Attempting to get my head wrapped around this solar info, very confused

NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
Hi all,
Have been lurking around the edges for the last couple of weeks and decided to ask some more dumb questions, that I don't have a clue to figure out.

A little background history,
We, better half and 2 grown kids, love to boondock/camp in all 4 seasons of the year, hunting/fishing seasons get the main use. Started with a tent and now have graduated to a 2007 28' KS Desert Fox TH RV. We want to install an Solar RV system (12 Volt), there is no solar equipment installed at this time.

I made a partical list of the items that I think should be used/run on this system,
figuring the total watts (from all items) I come up with this figure for winter time use:
1685 Watts used per day?

I came up with this amount, used per day (for all items), winter time use:
235 amp Hrs used per day?

There are some items I could not figure out, ie, Co detector and all other safety gear installed in the RV etc.

Being that I have limited space to install many batteries, I will probaly adapt this member ideas to my TH, as there is several bays that I can use, see photo's here:

http://www.flickr.com/photos/kayakmikesstuff/

I think that I would have to use AGM type batteries this way, as there is not much storage areas where I can use a 4 battery bank, plus the 2 OEM batteries on the tounge.

I don't think that reg LAB would work under the inside bed compartment, due to the stink/gassing etc. I cannot use the back bummper area as the TH has a ramp that lowers right over the back bumper etc. So I am kinda stuck with going underneath, for the battery storage area.

I want to have 3 KC 135Watt panels on the roof, no problem with installing them there. I think I am over board somewhat, but that is better than being underwater???

Here is a list of the following equipment, I think I need,
Mag inverter: Model MS-2012
Mag Controller head: ME-RC-50
Charge Controller: Tristar 60
Remote Temp sensor for above:
Trimetric Battery meter:

Total funds for above $2165 (estimated so far, still pricing around) out of $5000 allotted for this project, the remaining funds will be for panels, batteries, wiring etc.

I know from reading lots of posts here, to expect about an 80% working rate, as a general rule, because of ALL THE small losses in these solar systems etc.
Does this include for WINTER time use, IE, batteries are only 65% efficient at or near 32* temp?

I would greatly appreciate any and all help on setting up a good working bullet proof system to enjoy year round.
Tia,
Don

Comments

  • BB.BB. Super Moderators, Administrators Posts: 29,321 admin
    Re: Attempting to get my head wrapped around this solar info, very confused

    It would be very helpful to know where you camping is by season... Solar irradiance is very location/weather dependent.

    I will do Los Angeles for you--but anywhere else is pretty much the same. Using PV Watts, say you have 1 kW of solar panels, 0.59 system derating (AC power using AGM batteries), and you mount your panels flat to the roof (tilting when parked will give you more power the farther north you go):
    "Station Identification"
    "City:","Los_Angeles"
    "State:","California"
    "Lat (deg N):", 33.93
    "Long (deg W):", 118.40
    "Elev (m): ", 32
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.590"
    "AC Rating:"," 0.6 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 0.0"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","12.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 2.88, 47, 5.88
    2, 3.87, 59, 7.38
    3, 4.77, 82, 10.25
    4, 5.76, 95, 11.88
    5, 6.57, 112, 14.00
    6, 6.79, 111, 13.88
    7, 7.00, 118, 14.75
    8, 6.60, 110, 13.75
    9, 5.13, 82, 10.25
    10, 4.15, 69, 8.62
    11, 3.21, 50, 6.25
    12, 2.72, 43, 5.38
    "Year", 4.96, 976, 122.00

    Lets pick two numbers (because I am lazy) ~45 kWH per month for Winter; and ~100 kWH per month for summer--based on 1,000 watts of solar panels. You have 3x135 Watt = 405 watts of solar panels. For Winter (note, I have ignored the inverter losses below--If you had 12 volt only loads, you would get a bit more power than I showed):
    • 45,000 WH per day * 1/30 days per month * 1/12 volts = 125 Amp*Hours per day per 1,000 watts of panels
    • 125 WH * 405 watts/1,000 watts = 51 AH per day winter
    • 51 AH * 12 volts = 612 WH out the AC inverter
    And for summer:
    • 100,000 WH per day * 1/30 days per month * 1/12 volts = 278 Amp*Hours per day per 1,000 watts of panels
    • 278 WH * 405 watts/1,000 watts = 113 AH per day summer
    • 113 AH * 12 volts = 1,356 WH out the AC inverter
    So, based on what you asked for--I am guessing that you will generate around 1/4 the amount of power you want to use during the winter (although, I am not seeing how you converted between 1,685 WH and 235 AH)...

    So, this demonstrates that, for most people, they use more power than solar can generate based on their first pass calculations.

    Generally, the best way around the issue... First look at conservation... Use LED/CFL lighting, change out the forced air furnace with one that does not use 12 vdc. Look at using an LP powered refrigerator. Reducing the usage of other electronics (small netbook instead of large laptop, use as DVD player instead of standard TV+DVD player, etc.).

    Probably look at a good generator/battery charger combination that supports your battery bank needs (sized to battery bank). Run genset in the early morning to get the batteries > 80% charged--then less the solar take the rest of the day to finish off the charging (saves fuel and generator run time). Using the vehicle engine to recharge your RV bank is usually a poor use of fuel (and is hard on your vehicle engine/alternator).

    Adding more panels and tilting the panels when parked will add more power too.

    I will stop here--What questions do you have?

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Bill, thank you,
    I will attempt to answer your questions, I am in over my head, so bear with me, I will answer your questions/ statements which will be in bold, my answer or questions will be under neath your info.

    It would be very helpful to know where you camping is by season... Solar irradiance is very location/weather dependent.

    Where we will be, depends on where we are lucky enough to draw a tag for, I went to another site and used their info to get the following info for replies etc,as the site you had listed only shows a couple of towns listed near where we may end up.

    For the following areas:
    Ely area, Lat. 39/Long.114, I figured the average solar irradiance for the WINTER months is 4.69 hrs per day
    Elko area, Lat.40/Long.115, is approximately 3.75 hrs
    Winn area, 40/117 is approx 3.75 hrs
    Reno area, 39.119 is approx 4.25 hrs
    Lvlk area, 40/118 is approx 3.34 hrs per day

    The total average for above is 3.95 hrs per day, for WINTER use (across the areas we would been in the most), to figure how many panels/batteries I will need to have a reliable working system for winter use, summer use should be ok as I will have more hrs to replenish the power use from the system etc???

    although, I am not seeing how you converted between 1,685 WH and 235 AH.

    The 1685 Watt Hours per day used, (all electrical items used per day average) (is what I read on another site), is one method that can be use to figure out how many panels/batteries would be required.
    The 235 Amp hrs used per day was another way to figure out the required number of panels/batteries etc.

    Also figuring in that during the winter use, my average hours that would produce any power from the panel would be approximately 3.95 hrs per day??

    I figured it out this way: using KC 135 watt panels @ 7.39 Amp each

    3 panels @ 135 watts = 405 total watts x 3.95 h/per day (winter use) = 1599.75 watts, per my rough caluations i will use approximately 1685 watts per day = in the hole by 85.25 watts, not good. :cry:

    3 panels @ 7.39 amps each= 22.17 amps total x 3.95 hrs/p day = 87.57 total amps = 147 amps in the hole, not good, hole getting deeper. :grr

    I would need to have at least 8 panels to break even, not accounting for system losses, cold batteries etc. No room for that many panels.

    I cannot figure out how to make this info come out with the figures/information, I have so far. Some of the WH and A hrs are a SWAG, my Kill-a-watt meter has not got here yet to do a realistic check on all the electical draws for the TH.

    Generally, the best way around the issue... First look at conservation... Use LED/CFL lighting, change out the forced air furnace with one that does not use 12 vdc. Look at using an LP powered refrigerator. Reducing the usage of other electronics (small netbook instead of large laptop, use as DVD player instead of standard TV+DVD player, etc.).

    I plan on using LED lighting where ever possible, small 22-24" tv/dvd player, radio will be the only other electronics used. I am forced to use the furnace as the Th has a heated/ducted piping that keeps the ALL the WATER TANKS from freezing along with the internal water lines etc. I plan on tilting the panels as we stay for an average of 10days to 2 weeks when we go anywhere.

    As close as I can figure it so far, the furnace draws 8-10 amps per hr of use, I will have a cat heater that will be used most of the time for keeping heat inside the TH, but will be shut off during sleeping hours, so the furnace will be cycling off and on during the night etc.

    I already have 2-2000 Honda generators that will be used for back up if needed, to also back up the inverter/charger combo and other solar equipment listed in the first post. The vehicle will never be used as a power source, unless it's an emergency.

    I am doing something wrong, but don't know what, and I have not got to the batteries needed yet, and the hole is getting deeper by the minute.

    Thank you,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    For an RV, I would look at it this way:

    How many panels can you fit on the roof?
    Let's say 3 x 135w. So 405w per hour of good sun - that's the max you can harvest.

    Let's say you get 4 hours/day of good sun, and you use a good MPPT charge controller. Okay, say 85% of that harvest ends up in the batteries. That's 345w per hour x 4 hours = 1377 watt*hours per day you need to store.

    Divide that by 13.5v (true voltage for a 12v nominal system) and you are looking at about 100 amp*hours per day that you can harvest and store. To make the batteries last a long time, you want to discharge them no more than 50% so you need roughly double - so 200ah.


    So, if you can only fit 3 x 135w panels on the roof, and get 4 hours/day of good sun, then you only need 200ah of battery.

    And you have 100ah per day available for use. That's it. That's all you get so now you *must* make your loads fit that number.


    That's if you want to run the RV from the solar only. Depending on how long your trips are, you might be better off planning more battery capacity and top it off from shore power before you go out, and then use the solar to stretch it a bit.

    So lets' say your loads are 150ah/day and you can generate 100ah/day. You will incur a 50ah/day deficit.

    You could double the battery ah capacity to 400ah. On day one you run down 150ah to 250ah, then replace 100ah so now the bank is at 350ah. Day two you are at 300, day three at 250 and day 4 at 200 which is 50% drained.

    At that point, you need to run your generator and get them back to full charge. Be aware though that letting the batteries sit for a few days at noticeably less than full charge can noticeably shorten their life, but if you run the generator and top them off every 3-4 days they should last some years.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    DWH,
    Thank you for the info,
    Please do not think I am doubting or questioning your infomation, I am not in any way, I am attempting to understand via which method I should use to have a good working solar system for the RV.

    Using your info, why does figuring the problem out via the watts way, your ending results come out with 1377 watts*hrs divide by 13.5 voltsand you have about 100amp*hrs.

    Yet, when you figure the problem out via the amp way out the end results comes out a different results, (using the info from the panels, being 7.39 amps per panel x 3 panels = 22.17 Amps total x (3.95 hrs p.day) = 87.5 amps total.

    WHERE DOES THIS DIFFERENCE go?

    Figured by Watts = 100 ahr
    Figured by Amps = 87.5 ahr

    Difference of 12.5 ahr, What happened to it? Why would it not work out to be roughly the same totals? This amount is quite a lot to lose somewhere?

    I have been figuring this out for the last couple of weeks and getting no where, except splitting headaches.:grr I follow so far, the way you figured everything out.

    I know nothing about solar equipement or the way it works, attempting to learn.

    I had planned on a 4 battery bank (underneath the th) for the solar set up and have 2 OEM 12 volts on the tounge at this time. I know that the 2 OEM 12 batteries will NOT RUN THE FURNACE thru the night, reason for the solar set up.

    I have room on top of RV for 4/135w sized panels.

    Thank you,
    Don
  • BB.BB. Super Moderators, Administrators Posts: 29,321 admin
    Re: Attempting to get my head wrapped around this solar info, very confused

    First of all, there are losses that you are not accounting for...

    Basically, there is the 77% efficiency (typical) of the solar panels + charge controllers. Then there is the 80% efficiency of flooded cell batteries or 90% efficiency of AGMs. Then there is the 85% or so efficiency of the AC inverter. For a typical full off-grid system with flooded cell and and an AC inverter:
    • 0.77*0.80*0.85 = 0.52 or ~52% of the solar panel rating gets turned into useful energy at the 120 VAC inverter outlet.
    Next, for charging/discharging batteries, there is a difference between Watt*Hours and Amp*Hour calculations.

    Lead Acid Storage Batteries (excluding during equalization) are pretty close to 100% efficient when looking at Amp*Hours out and Amp*Hours recharged.

    The power (Watt) losses come from the battery supplying about at 12.0 volts or so and recharging at 14.5 volts:
    • 12.0 volts discharging / 14.5 volts charging = ~83% efficiency
    So--Depending on how you do your calculations, and even what type charge controller you have (PWM or MPPT)--Some calculations are "easier" in Amp*Hours.

    However, in the end, we tend to do most of the calculations in Watts and Watt*Hours so we can take losses into account... That 50% loss from panel rating to inverter output is real (and ugly :cry:).

    You can look at the difference between AGM and Flooded Cell... Operating a battery between 75% and 90% state of charge is more efficient than 85% and 100% state of charge, etc... But--for solar, if your "numbers" are within 20% of the actual measurements--consider it a a win... There is just so much variability in how you operate your system, what specific components you purchase, and variability in weather--it is not worth the effort to be more accurate (the additional accuracy is an illusion).

    So, say you are using 3x 135 watt panels, AGM batteries and most of your power is AC (using 3.95 hours of sun in winter):
    • Derating = 0.77 * 0.90 AGM batt * 0.85 Inverter = 0.59 efficient
    • 3x 135 watt panels * 3.95 hours of sun per day * 0.59 sys derating = 944 WH per day (winter)
    • 944 WH * 1/12.0 volts * 1/0.85 back out inverter losses for DC only loads = 92.5 AH of 12 volt DC per day (roughly)
    The numbers are ugly--I am sorry about that. I (we) usually try to error on the conservative side (batteries age, panels get dirty/blocked by trees/shadows at times, etc.).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    WHERE DOES THIS DIFFERENCE go?

    It disappears into The Black Hole of Mathematics. :D

    Amperage is Wattage divided by Voltage.

    To make it easy, say a 120 watt load.

    120w / 120v = 1a
    120w / 12v = 10a

    But 12v systems aren't actually 12v - at full charge they are more like 13.5v, which would actually look like:

    120w / 13.5v = 8.8a

    So the differences you are seeing in the math, are due to differences in the numbers that are being plugged into the formulas.

    Watts are the main thing. Amps vary depending on the voltage and when dealing with "12 volts" you can actually be talking about anywhere from 11v-14v (for batteries) and from 17v-23v (for solar panels). Those voltage variables tend to jerk around the amperage numbers.

    The best way is to do the math in watts, then convert to amps where needed.


    Also, you can't rely on the numbers from the panels to get an accurate picture. For instance, say a PV puts out 7amps at 17 volts.

    Well, if you use a PWM charge controller (just direct connects the PV to the battery) you aren't going to get 7a into that battery, because the panel voltage is 17 and the battery voltage might be 11, 12 or 13 or somewhere in between - and the mismatch will cause inefficiency because the voltage differential is pretty high. The battery simply cannot absorb as much power as quickly if it is coming it at so high a voltage.

    If you used an MPPT controller, it will lower the voltage from the PV so that the MPPT is pushing like 15v to the battery instead of 17v - and that is much more efficient because the battery can absorb more of it faster. AND since you are lowering the voltage, you are increasing the amperage (amp=watt/volt) so you might actually see 8a or 9a going into your battery from a 7a PV panel (lowering the voltage to kick up the amperage is the beauty of MPPT).

    Actually, it would look like this:

    17v x 7a = 119w

    119w / 17v = 7a
    119w / 15v = 8.4a


    As Bill mentioned, there are still system losses and inefficiencies. Voltage mis-match, wiring losses, etc. That's why I said maybe 85% will actually get into the battery. That's just a guess though. Most MPPT charge controllers are more efficient than that, but there is still a voltage mis-match to the battery (though it's small with MPPT) and also batteries have internal resistance - the more drained they are, the more their internal resistance and the less they will absorb.

    I have room on top of RV for 4/135w sized panels.

    Thank you,
    Don

    Then you should probably plan on using 4.

    I'm Don too. :D
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    DWH and Bill,
    Thank you for helping me, I just could not figure out where the rest of the amps was going etc.

    I did not realize that solar systems were that inaffecient (realitve speaking), knowing this info, I see where a person has to figure in some extra to get anything near what they were looking for, (to a certain point).

    By using the best equipment, ie, MPPT charge controller, and uping the wire size a couple of sizes, and any other reasonable improvements, can the efficiency be brought up some?

    So, change of plans, there will be 4, 135 Watt panels, +4 batteries, I have not made up my mind if these batteries will be 6v or 12V, is there any real advantage of one over the other?

    I am about 75% sure that they will be AGM types due to the way they will be mounted underneath between the frame rails, see pictures of mounting system here:
    http://www.flickr.com/photos/kayakmikesstuff/,
    I will adapt this members ideas etc to my setup.

    The following is a list of the equipment that will also be used in this solar setup,
    Mag inverter: Model MS-2012
    Mag Controller head: ME-RC-50
    Charge Controller: Tristar 60
    Remote Temp sensor for above:
    Trimetric Battery meter:
    2- 2000 Honda Generators (already have)

    Are there any looming problems or better equiptment I can use with my setup, etc? My biggest concern is the furnace (The amp HOG) and having it run during the night to keep the tanks from freezing etc.

    Thank you guys again,
    now I'll go figure out the 4 panel system:cry:
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    By using the best equipment, ie, MPPT charge controller, and uping the wire size a couple of sizes, and any other reasonable improvements, can the efficiency be brought up some?

    Not really. Once you have the right stuff then you just end up chasing the Holy Grail of another tenth of a percent in efficiency.

    Wire size is extremely important to minimize voltage drops in low voltage systems. A 6v drop in a 120v system is only 5%, but in a 12v system that same 6v drop is 50%. The importance of properly sized wire and good solid connections cannot be overstressed.

    There is a voltage drop calculator that is often linked to in this forum. Maybe in the FAQ? I haven't played with it myself, so I don't have the link.

    So, change of plans, there will be 4, 135 Watt panels, +4 batteries, I have not made up my mind if these batteries will be 6v or 12V, is there any real advantage of one over the other?

    Not much difference really. Either 6v or 12v is just a collection of 2v cells. 200 lbs. of 2v cells is 200 lbs. of 2v cells regardless of how they are rigged for voltage.

    A 12v battery that has 225ah of capacity, will weigh roughly double that of a 6v/225ah battery, so you'll probably end up with about the same ah of storage capacity either way you go.

    Unbalanced wiring of the batteries can be a problem, in that wherever the resistance is lowest is where the most juice will come from, and the most charge will go - so that will end up wearing out first. Series connected doesn't have that problem, but parallel does.

    So if you rig two 6v in series to get 12v, then parallel those you only have to worry about balancing the resistance of two "strings", vs. rigging four 12v all in parallel you have to worry about balancing four "strings" (even though each string is actually only one battery).

    Around here, the standard link to "how to wire up batteries and why" is this:

    http://www.smartgauge.co.uk/batt_con.html

    The SmartGauge tech section is one of the best resources on the net. I HIGHLY recommend reading everything there.

    I believe you said something about having some batteries underneath and two on the tongue or something like that. If you try to combine the two, you are going to run into resistance imbalance problems. Your best bet in that situation is probably to split the loads and then use a 12v-12v battery charger to keep the smaller bank charged off the larger bank.


    Your battery rack is very cool! But that hinge makes me nervous. That seems like a lot of weight for that hinge to support.

    I would definitely go with AGM down there. They won't outgas and corrode the underside of your trailer, and they won't mind being tilted when you drop the rack. Also, having to check water levels by dropping the rack and removing the batteries regularly seems like just too much work.

    The Magnum MS2012 has a 100a charger, which might be a bit much depending on the size of your battery bank. For a 600 ah battery bank, 60a-70a would probably be about right. In charge mode the MS2012 draws 15a of AC which is more than the 13.3a continuous rating of a single Honda eu2000i. But you can program the MS2012 to use a lower charge rate - which will match the charge rate to your battery bank size AND should be able to run off a single eu2000i (if there are no other AC loads).
    Are there any looming problems or better equiptment I can use with my setup, etc? My biggest concern is the furnace (The amp HOG) and having it run during the night to keep the tanks from freezing etc.

    Ugh. Yea that's a problem. I believe you said you also have a catalytic heater? So you could get by without running the furnace at all if you didn't have to keep the tanks from freezing?

    There are tank heaters that are basically like water bed heaters - but I doubt they'd save you much in terms of watts. They might though depending on what your furnace draws.

    Another alternative might be to install a smaller propane furnace to keep the tanks from freezing and provide some heat in the cabin, and using the catalytics as well. Maybe something like the Propex:

    http://www.propexheatsource.co.uk/air-heaters.php

    Here's a dealer in the U.S.:

    http://www.van-cafe.com/home/van/page_316_205/propex_propane_heater_hs2000_kit.html

    And another:

    http://westyventures.com/propex.html

    Both of those dealer's pages list incorrect amperage draw for the HS2000 - one says 1.2a and the other says 1.8a...but the Propex page says 1.4a.

    So, the 6500btu HS2000 would draw 34ah per day running 24/7. Even the larger 9000btu HS2800 would only draw 46ah/day. But they are thermostatically controlled, so you could maybe stick the thermostat in with the tanks and set it to like 40 degrees or something...then the little Propex would only run enough to keep the tanks from freezing and would probably draw a lot less ah/day.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    DWH
    Thank you for the Smartgage info page, outstanding info I can mostly understand, I will read everything on that site several times.

    The battery rack hinge will be made of 1/4" material and grade 5 bolts for locks, I OVER build anything I do, as it will hold 4 batterys underneath, I also plan on insulating that bay with R-Max rigid foam, along with all other areas not covered and insulated etc, and that should help in maintaining a some what warmer temp around the batterys etc.

    I have to run the furnace, it is the only way to keep all the tanks from freezing, I just got back from one hunting trip and I timed the furnance, it runs for 5-6 minutes every 90 minutes, when set at the lowest setting of 55* possible, outside air temp was 27-30* everynight. I run the genset/furnace for several hours when we get back to camp, but will shut it off untill in the am when making breakfast, but hate the noise etc.

    I am in the process of building a water/wind proof skirting around the TH,s base, the built in genset has a fan for the hot engine air exhaust (NOT THE EXHAUST PIPE), that is directed to the ground, right under the genset. I am hoping I can use this hot engine air (being trapped by the skirting) to contain and store as much as posssible, untill the furnace has to be used during sleeping hours.
    Tia,
    Don
  • bryanlbryanl Solar Expert Posts: 175 ✭✭✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    A key for RV solar systems is to not over-engineer. It can be fun but the variables are many and the quantities also have significant variances. Experience will predict outcomes much more effectively than power engineering.

    You figure about 250 AH at 12v or 3KwH daily energy usage? That suggests a battery bank capable of providing 6 to 10 KwH energy storage. That means 600 to 1000 pounds of battery and 600 to 1000 watts of solar by the usual rules of thumb.

    Since it isn't likely your RV will support that weight of battery or that much solar, what you are looking at is a severely constrained system that requires [major] lifestyle adjustments and other compensation.

    Worrying about the CO alarms and other background loads in this context is rather fruitless. They are continuous and that means they do add up, though. (maybe 200 Wh/day or a tenth of your estimated usage)

    What makes the most impact are temperature, use profile, cycle to cycle variance, battery age, and other factors that may each impact available battery capacity by up to 20%.

    As for AGM's, they are nice but you should still provide proper battery compartments for your batteries. It is best if all bank components are mounted in close proximity.

    The usual process is one of continual adaptation and adjustment and improving solutions to suit preferences. This often includes upgrading RV's as energy is only one part of the entire equation. Good Luck and Have Fun!
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Have been reading the Smartgage info pages again.

    The #3 option looks to be the best for me so far.

    Question,
    When building the battery connection cables, keeping them ALL the same length, is it better to just hammer crimp or solder and crimp these wires to the lugs/posts.
    Does it make a difference?

    I want to make the best bullet proof system possible to stop the possibility of ANY loose connections, as this TH get dragged over some very rough roads etc.

    Using the #3 diagram for battery connection points, would it be better to use the proper sized copper pipe and then use the post/wing nut or post and clamp type battery connectors for each side of the battery bank.

    Attempting to figure the best attachment system where each side of the 4 battery's connect to the single point before the cable that enters the TH to be hooked into the system.
    Tia,
    Don
  • BB.BB. Super Moderators, Administrators Posts: 29,321 admin
    Re: Attempting to get my head wrapped around this solar info, very confused

    In general, a proper crimp connection is the best.

    A solder connection or solder+crimp are both "bad"....

    Solder only, if the wire overheats, the solder melts and the connection fails.

    Solder or Solder + crimp: The solder creates a fulcrum where all bending stresses are focused--leading to early failure as the copper work hardens and fails.

    A proper solder crimp will be gas tight and will not let solder in anyway. If solder can wick into the joint, then it was not a good crimp in the first place.

    Heating the crimp connector to solder--I worry that the the crimp joint can "relax" as the previously work hardened crimp softens from the heat. (proper soldering temperatures may not get the crimp hot enough to soften).

    If you decide to solder--then the joint/wire needs to be well supported to prevent the wire from flexing at the joint / work hardening and failing.

    On the other hand--I too have soldered my share of copper wire and cables when I had nothing else better to make the connection.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Hammer crimp for sure.

    I wouldn't use copper pipe on a rough road rig - too much chance of vibration/flex/break. Stationary in a building would be okay, and probably okay in a big boat, but on a camper or small boat I'd stick to fat cables.

    I'd prefer the ring terminals and wingnuts instead of the post and clamp. Down below the way you are doing it...I might chuck the wingnuts and go for a double nut or a nylock.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Thanks Guys
    For the info,
    My main concern was were the 4 battery leads/ends come together and the single line leaves each side, (In #3 digram of the Smartgage info pages.)

    Would you use brass, copper or steel bolts for this connection point? (five battery cable connections), for the least resistance for this system?

    I think I would have to build some type of box/holder to keep both of these junction points from flopping around and making any contact with the metal frame and then have that secured in place etc.

    Possibly use a capped piece of 2-3" PVC pipe at the junction point, making sure the connection joint is secured inside the pipe and then the PVC pipe is secured to the battery rack/frame to allow NO movement or metal contact etc.

    Which material/metal would have the LEAST resistance?
    Could a meter be used to test these materials for resisitance?

    Any suggestion/Ideas would be greatly appreciated.
    Tia,
    Don
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    DWH

    In reference to the copper pipe, I was thinking about using a 4-6" long piece of copper pipe (of the proper outside diameter/size) and then use those battery termanials that slip over the battery posts and have either a stud or clamp for wire attachment.

    Attach these battery clamps to the ends of the 4 battery cables and then slide these clamps over the copper pipe and tighten them down, then smash the end of the copper pipe and attach the main battery lead to that and securely mount the copper pipe so it does not make any contact with the metal frame,etc.

    I would probaly put a HD fuse on each main line for added security. Just thinking of the best way as this is all new to me, and still learning.
    Tia,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    DWH

    In reference to the copper pipe, I was thinking about using a 4-6" long piece of copper pipe (of the proper outside diameter/size) and then use those battery termanials that slip over the battery posts and have either a stud or clamp for wire attachment.

    Attach these battery clamps to the ends of the 4 battery cables and then slide these clamps over the copper pipe and tighten them down, then smash the end of the copper pipe and attach the main battery lead to that and securely mount the copper pipe so it does not make any contact with the metal frame,etc.

    I would probaly put a HD fuse on each main line for added security. Just thinking of the best way as this is all new to me, and still learning.
    Tia,
    Don


    Oh...uh...

    Busbar.

    http://www.google.com/images?q=marine+battery+busbar&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=og&sa=N&hl=en&tab=wi&biw=1366&bih=593


    EDIT: And yea, a fuse per paralleled battery or per series string of batteries. Basically, one fuse per paralleled whatever.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    dwh wrote: »
    Oh...uh... Busbar. EDIT: And yea, a fuse per paralleled battery or per series string of batteries. Basically, one fuse per paralleled whatever.

    Dwh
    Thanks for the info, (have saved the page and reading everything)
    I did not know what this piece of equipment was called = Busbar, (I am slowly learning) and was wondering if they would handle the wire size needed for this application?

    How can they be attached and provide NO contact with anything that will conduct elect power?
    Which would be the best material, Copper, brass or Alum?

    Tia,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    How can they be attached and provide NO contact with anything that will conduct elect power?

    Technically...they can't. I mean, they do have to connect to the battery cables and they are conducting power.

    Just kidding. I know what you mean. :D

    Plastic mounts called standoffs. Get em in red or black.

    Which would be the best material, Copper, brass or Alum?

    Copper or Aluminum, but as long as the busbar is rated for the amperage, it doesn't much matter. I mean, you will have copper battery cables, but the connectors crimped on the end won't be copper and the bolts on the busbar will be steel.

    There is a member on the forum here, 2manytoyz who has a site with a good deal of info and pics. He made his own busbars and did a nice job of it. Should give you an idea how it can be done:

    http://2manytoyz.com/battbank.html
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    dwh wrote: »
    Copper or Aluminum, but as long as the busbar is rated for the amperage, it doesn't much matter. There is a member on the forum here, 2manytoyz who has a site with a good deal of info and pics. He made his own busbars and did a nice job of it. http://2manytoyz.com/battbank.html

    Dwh and guys,
    Thank you, the site info on 2manytoyz was a big help.

    Question: When bus bars are made from solid copper/brass ie, (like 2manytoyz), how can the amps be measured ? Will a meter provide a correct reading OK?

    Which would be the better option, solid copper/brass bar 3/4" wide x 1/4" thick x required inches long to properly fit or #2 copper cable for the battery connections, using #3 diagram in the smart gages pages?

    I have a Lathe, Mill and welder etc, and I can build just about anything, (Gunsmith for 20+ yrs). I can make solid bolts from copper/brass etc and have 20-40-60- ton presses for forming etc. I can form different sizes of copper pipe into cable lugs (20 ton press, no problems). :D
    Tia,
    Don
  • nsaspooknsaspook Solar Expert Posts: 396 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    Dwh and guys,
    Thank you, the site info on 2manytoyz was a big help.

    Question: When bus bars are made from solid copper/brass ie, (like 2manytoyz), how can the amps be measured ? Will a meter provide a correct reading OK?

    Which would be the better option, solid copper/brass bar 3/4" wide x 1/4" thick x required inches long to properly fit or #2 copper cable for the battery connections, using #3 diagram in the smart gages pages?

    I have a Lathe, Mill and welder etc, and I can build just about anything, (Gunsmith for 20+ yrs). I can make solid bolts from copper/brass etc and have 20-40-60- ton presses for forming etc. I can form different sizes of copper pipe into cable lugs (20 ton press, no problems). :D
    Tia,
    Don

    We use some of these products for DC high current systems. I'm sure you could make your own with the equipment you have.

    http://www.stormcopper.com/busbar.htm
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    Question: When bus bars are made from solid copper/brass ie, (like 2manytoyz), how can the amps be measured ? Will a meter provide a correct reading OK?

    You don't really measure the ampacity of a bus bar - you calculate it. Here's an ampacity table:

    http://www.stormcopper.com/design/Ampacity-Quick-Chart.htm

    If you need to measure, for instance with a battery monitor, you use a shunt. That goes in the negative line between the battery bank and whatever. So you would connect the 3 battery string negatives to the negative bus bar, connect the shunt to the bus bar, and connect the inverter and solar charge controller negatives to the other end of the shunt. That way the shunt -> meter can track input/output to the total battery bank.

    http://search.store.yahoo.net/wind-sun/cgi-bin/nsearch?catalog=wind-sun&x=0&y=0&query=shunt


    One thing that has occurred to me more than once when looking at 2manytoyz' bus bar setup, is that it doesn't seem to be strictly balanced. He's got 2x6v in series for 12v, and then runs those strings to the bus bar.

    Notice how he has his short jumper quick-disconnects. The first one goes to the lowest position on the bus bars, the next to the second lowest, etc. Then the inverter and charge controller connections are at the other end of the bus.

    http://www.2manytoyz.com/hardware/alt/setup_1482.jpg

    (at least, that's how it looks to me)


    That would seem to me, to make the string connected furthest up from the bottom (closest to load/charge) do the most work. I think it could be balanced a bit better by putting the charge/load in the center, and putting the battery strings on either side.

    For instance, something like this:

    + bus
    string 1 +
    string 2 +
    inverter +
    charger +
    string 3 +
    string 4 +

    - bus
    string 3 -
    string 4 -
    inverter -
    charger -
    string 1 -
    string 2 -

    string1+ furthest from the charger, but string1- closest to the charger
    string2+ nearest the inverter, but string2- furthest from the inverter
    string3+ nearest the charger, but string3- furthest from the charger
    string4+ furthest from inverter, but string4- closest to the inverter

    It just seems to me that sort of arrangement would work out to a more balanced charge/discharge across all the strings.

    Maybe flipping the inverter- and charger- would balance it out a bit more. Unfortunately, I just don't seem to have the math skills to work out the exact correct arrangement, so I'll have to leave it to the engineers (it's a union thing). :D
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Thanks Dwh

    I see what you are saying about the examples/pictures of 2manytoyz.
    It appears that may be the case. I would think (what little I know about this stuff) that your reasoning on balancing the system might be a better way, kinda like the #3 example in the battery setup etc.

    After spending the last couple of days crawling and rolling around underneath the DF, attempting to find a suitable spot for the battery rack etc (4 AMG batteries, via Kayakmikes design), several questions have jumped up.

    Per information I have recieved, it is best to keep the invertor within 10' or less of the batteries, the pending cable length/run will be approx 12' -13'. See the explanation below.

    Because of the DF lack of outside storeage bays, the best I can do at this time, is the battery rack between the dual axles underneath, then run the #2 cables up the passenger side main frame rail and into the furnace/reefer/closet area, (size is 24" deep x 44" wide, the furnace/reefer (left side) is 28" wide x 24" deep and the right side is a closet/shelf storeage area 16'' wide x 24" deep floor to ceiling). The Solar Panel wiring from the roof will drop down thru the reefer exhaust area (same area).

    Inside the right section of this area, is the OEM Intelipower 9260 power converter that is bolted to the floor, approximately 9" above this converter is a drawer 8"H x 14"W x 22''L, then 5'' to the bottom of the storage area.
    Since this is the best place (so far), I can convert this area to store/place most all of the pending solar equipment, by removing the drawer and installing a couple of shelves for the pending equipment.

    The viewing meters can be installed on the left or right sides of this storage area with no problems, via running the wires inside of this cabinet to either side.

    The pending solar equipment is as follows:
    Mag inverter: Model MS-2012
    Mag Controller head: ME-RC-50
    Charge Controller: Tristar 60
    Remote Temp sensor for above
    Trimetric Battery meter:
    4-135 KC Panels
    4 AGM battery's

    Will the extra few feet degrade my solar setup?
    What about upsizing the battery to invertor wire a size or two to make up for the extra distance etc.

    With the pending Solar install, do I remove the OEM power convertor?
    I would like to use it as it has the capability of charging 2 different size/kind of battery racks, the AGM and the 1-2 12v tounge battery, (deep cycle), which can not be done with the new solar equipment.

    Just pull the fuses and leave it there and keep as a back up?

    Any thoughts or suggestions on the best direction to head.
    Tia,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    Will the extra few feet degrade my solar setup?

    You have two different things to consider - the voltage/amperage from the solar to the battery bank, and the voltage/amperage from the battery bank to the inverter.

    First - solar controller to batteries:
    4 x 135w @ 12v (nominal) panels in parallel would be 540w @ 12v.
    540w / 12v = 45a

    Okay, so sticking that number into a voltage drop calculator with #2 wire:
    http://www.currentsolutions.com/vdrop.php
    The drop on a 45a load over 10' (20' in the calculator) would be 0.15v, and over 13' would be 0.19v.

    1% of 12v would 0.12v.

    So, even at 13' the voltage drop for 45a over #2 wire would be under 2%, which is close enough.


    Which doesn't actually matter at all anyway...because...


    Now for the battery bank to the inverter:
    The MS-2012 has a rated DC input of 190a @ 12v.

    Note that the manual actually says a run of "#2/0" should be under 5'".

    http://www.wholesalesolar.com/pdf.folder/inverter%20pdf%20folder/Magnum%20MS%20Manual.pdf

    (page 8 )

    2/0 is two-ought - and that's a helluva lot bigger than #2...in fact try putting those numbers into that calculator - 12v. 190a. 26', #2 wire...it pops up a message saying don't do over 170a on #2 because the wire temp would be over 80C!
    What about upsizing the battery to invertor wire a size or two to make up for the extra distance etc.

    Yea...you gotta. Plug in 12v, 190a, 26', 2/0 wire and you get a drop of 0.30v which is coming up on 3%. If you kicked the wire size up to 3/0, then it would get you down to 2% voltage drop.

    In the manual for the inverter at he bottom of page 11 they have a table showing recommended wire size. For 5'-10' they show 4/0. 4/0 is THICK. Hard to bend. Very hard to bend. So when you get up in that range, you need to use welding cable which is much more flexible. NAWS sells the kit you need:

    http://store.solar-electric.com/15foincase40.html


    Note that the manual also says you should use crimped ring terminals with a 5/16" hole to connect the cable to the inverter - so make sure the cables have the right terminals before you order them.

    or...

    Not to cheat NAWS out of a sale, but what I would probably do is take the inverter to a welding supply shop and have them cut me the wire and crimp on the connectors. They usually have spools of the stuff and the connectors and crimping tool. Call first and make sure they can do it and get a price.


    But also...if you are gonna run a pair of 4/0 up from the battery bank bus to the inverter, then you could connect the solar charge controller to that wire at the top. 4/0 is big enough to handle the 100a from the inverter's charger AND the 60a from the MPPT at the same time. Especially considering that the inverter's charger won't even be running unless you're connected to shore power. You really don't need two runs down to the battery bank. You can just stick a 60a fuse in a short run of #2 and connect it to the inverter end of the 4/0.

    You need a big (250a) fuse between the battery bank + bus bar and that 4/0 run to the inverter. The fuse has to be down at the bus end, not up at the inverter end. If you have the fuse at the top and there is a short, then the fuse will blow and protect the inverter, but the battery will still be feeding power to the whole 15' run of 4/0. If there is a short in that sucker you want the fuse to blow at the battery end and kill the power to that 4/0.


    With the pending Solar install, do I remove the OEM power convertor?
    I would like to use it as it has the capability of charging 2 different size/kind of battery racks, the AGM and the 1-2 12v tounge battery, (deep cycle), which can not be done with the new solar equipment.

    Just pull the fuses and leave it there and keep as a back up?

    It depends - how many amps does it put out?

    Can your DC distribution box draw power from two different battery banks? Probably not. So you have to choose which battery bank you are going to use to feed your DC loads.

    What you might do is put in a switch, so that you could run your DC from the big bank, and switch to the tongue bank if needed. In that case, I would let the solar and the inverter/charger handle charging the big bank, and let the existing converter/charger handle just the tongue bank. You would have to wire both the inverter/charger and the converter to get AC power from shore or generator.

    You could also rig the converter to charge both banks, AND have the inverter/charger AND the solar charger on the big bank. They won't conflict, but they might total up to more amps of charging than is healthy for your big bank. Also, having both the converter and the inverter/charger drawing off a wimpy little campsite 15a shore power circuit might be too much and pop the breaker to your campsite.


    If you just pull the fuse and leave it as a backup - what will charge the tongue battery bank?

    In reality, you should run the DC off the big battery bank, and use the solar and inverter to charge that bank and dump the tongue bank completely. Then you could wire the existing converter to feed the big bank and leave it turned off unless you need it.



    Also note that the solar charge controller and the inverter/charger each has its own battery temp sensor - you need to use both.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Dwh,
    Thank you for the info,
    more learning and reading to catch up on.

    I follow the info about the panels/controller to batteries producing the 45 amp of power etc.

    But I am lost, when it comes to the Mag inverter and 190a @ 12v, Where did the extra 145 amps of power come from?, when I only had 45 amps to start with from the panels, that is what I have to work with???? Correct. I am in over my head again. :confused:

    Quote: "Especially considering that the inverter's charger won't even be running unless you're connected to shore power".

    99.9% of the time we will be boondocking, with NO power of any type provided, except what we have with us or bring. I don't do camp grounds, or never have in the last 40+ yrs of tent camping etc. If by chance we end up in a camp ground, then I quess I'll have use the supplied electrical power.

    Quote: "It depends - how many amps does it put out?"

    Per information from the users manual, which states: 9260 series has 4 operating modes, Boost,Normal,Storage and Equalize. Output voltage is for normal is 13.6v DC, Boost mode is 14.4V DC, Storage mode is 13.2V Dc and Equaliztion Mode is 14.4V for 15 minutes, every 21 hrs of use.
    Output is 60amps at 13.6V DC.
    Model 9260, 1000 watts, www.progressivedyn.com

    Quote: "If you just pull the fuse and leave it as a backup - what will charge the tongue battery bank?"

    I don't know yet, Can a small portable standard electric battey charger (ie Sears type) be run from the big 4 battery solar set up to charge the 12V trolling motor battery (tounge battereis) when needed and not cause any major problems?
    If so, I can remove this OEM converter and one less problem to deal with.

    Quote: "Also note that the solar charge controller and the inverter/charger each has its own battery temp sensor - you need to use both."

    I had planned on using all the available temp sensor's for each piece of equipment that requires it, to have the best trouble free system possible, within reason.
    TIA,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    But I am lost, when it comes to the Mag inverter and 190a @ 12v, Where did the extra 145 amps of power come from?, when I only had 45 amps to start with from the panels, that is what I have to work with???? Correct. I am in over my head again. :confused:

    Ah...heh.

    Okay, first let's define "the bus". The bus is the power distribution apparatus - i.e., the bus bars AND the 4/0 cable. It's all just a rig to allow power to flow from here to there (and back if need be).


    The solar system provides 45a TO the bus. The inverter draws (up to) 190a FROM the bus. Two different things going on there.


    So the way it works, is that if the solar were supplying 45a to the bus, and at the same time you racked the inverter up to max load - the inverter would draw 190a from the bus ... 45a of which is supplied to the bus by the solar charge controller, so the other 145a is supplied to the bus by the batteries.

    If you then turned off the inverter, the 45a supplied to the bus from the solar would flow to the batteries instead. Since the solar charge controller is connected to the bus at a higher voltage than the batteries, the power would flow from the higher voltage to the lower (that's how chargers work).

    EDIT: But let's say you don't have much running from the inverter. Say it's pulling 20a from the bus and the solar is supplying 45a to the bus. Well, 20 would go to the inverter, leaving 25a to go to the battery bank.

    And of course, at night if you max out the inverter, the whole 190a comes from the batteries since the solar is supplying nothing to the bus.


    Also, the inverter isn't just an inverter, it's an "inverter/charger" which is two devices in one box. So, when you have the shore power plugged in, the inverter stops pulling FROM the bus, and instead switches on the battery charger, which supplies up to 100a TO the bus. It also passes the 120v coming in from the shore power straight through to the 120v plugs. It uses a transfer switch to disconnect the inverter's 120v plugs from the inverter section, and instead connect them to the 120v incoming shore power - it doesn't need to invert 12v to 120v is there is already 120v coming in.


    Since your MPPT controller can supply up to 60a to the bus, you need wire from the solar charge controller to the bus that is rated to carry OVER 60a, and you need a fuse rated at OVER 60a, but UNDER the wire's max rating. The purpose of the fuse is purely to protect the wire from melting.

    (Actually, since you are not using the full 60a rating of the controller, you can just use a 60a fuse - it will blow long before #2 starts to melt and still be high enough not to blow from a 45a load).

    Since the inverter can draw up to 190a from the bus, you need wire that can supply 190a to the inverter. 4/0 is rated quite a bit higher than 190a, so you need a fuse higher than what the inverter can draw, but less than what the wire can handle. One doc I saw on that inverter said it draws up to 190a, another one said up to 200a. Okay, well a 250a fuse is high enough that the inverter won't blow it, and low enough that it will blow long before the 4/0 starts to melt.



    Quote: "Especially considering that the inverter's charger won't even be running unless you're connected to shore power".

    99.9% of the time we will be boondocking, with NO power of any type provided, except what we have with us or bring. I don't do camp grounds, or never have in the last 40+ yrs of tent camping etc. If by chance we end up in a camp ground, then I quess I'll have use the supplied electrical power.

    Yea, same here. But I DO have a generator, which is the same thing really.

    The point was that the 4/0 that you need for the inverter to suck 190a FROM the batteries, is of course perfectly adequate for the chargers to push 100a+45a the other way TO the batteries.


    Quote: "It depends - how many amps does it put out?"

    Per information from the users manual, which states: 9260 series has 4 operating modes, Boost,Normal,Storage and Equalize. Output voltage is for normal is 13.6v DC, Boost mode is 14.4V DC, Storage mode is 13.2V Dc and Equaliztion Mode is 14.4V for 15 minutes, every 21 hrs of use.
    Output is 60amps at 13.6V DC.
    Model 9260, 1000 watts, www.progressivedyn.com

    Yea. If you were pushing 45a TO the batteries from the solar, and another 100a from the inverter/charger and then ALSO added another 60a from that converter - you'd potentially have as much as 205a of charging current pushing to the batteries.

    That's very likely higher than the batteries are rated for. The rule of thumb is 10%-15% of whatever the amp hour rating of the battery bank is. So if you had say 4 12v 225ah batteries in parallel, the amp hour rating of the battery bank would be 900ah. So the charge current should normally be in the 90a-135a range.

    Some batteries can take higher charge currents - lots of AGMs can - but you have to check the specs on yours.



    Quote: "If you just pull the fuse and leave it as a backup - what will charge the tongue battery bank?"

    I don't know yet, Can a small portable standard electric battey charger (ie Sears type) be run from the big 4 battery solar set up to charge the 12V trolling motor battery (tounge battereis) when needed and not cause any major problems?
    If so, I can remove this OEM converter and one less problem to deal with.

    Ahh. So the tongue batteries do have a purpose and need to be charged.

    So, you rig the trailer's DC to get power from the solar battery bank (actually from the solar battery bank BUS).

    You have no shore power AND you have no generator. The only charging power is coming from the solar charge controller.

    How do you charge the trolling motor batteries?

    Well, yea you could use a small charger that plugs into the 120v side of the inverter. That's a bit inefficient though since some watts are wasted when the power goes through the inverter.

    You could even plug in that 60a progressive converter/charger. (FYI - INverter takes DC and makes AC, where CONverter takes AC and makes DC.) But that's inefficient as well (wasted watts).

    Another way would be a DC-DC charger. Something like this:

    http://www.powerstream.com/DCC.htm

    That will take power from your big battery bank and charge your smaller bank. More efficient, but you'd need to make sure that your trolling motor battery didn't drag down your house bank too far.

    Another way would be another solar panel and charge controller just for the trolling motor batteries.

    The problem is that if your only incoming power is the solar, then whatever is going into your trolling batteries is NOT going into your house batteries. Or it is, but then it's going right back out. Whatever power you use to charge the trolling batteries comes out of your total daily power budget.



    Personally, I'd carry a small inverter generator for recharging everything when the solar just isn't enough....oh wait - I DO carry a small inverter generator (actually, my camper doesn't have solar, so I fire up the gen every couple of days when I'm camping to recharge the house battery).
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Dwh
    Thanks for the explanation on the inverter/operations etc.

    I now see why you have to figure the use of the 4/0 wire, (working with/to the possible maximum of the solar system equipment installed), not just what is quoted by the panels. :blush:

    I also have 2-2000 Honda gen sets, so I will adapt it (OEM converter) to charge the trolling motor battery's on a seperate stand alone system when needed.

    The pending solar setup/system equiment will a better choice due to the AGM battery's being used and the special requirements needed (charging voltage/time etc).

    I did not realize that so many operations/functions of equipment, and being used in different ways thru all these parts at the same time. I will diagram my complete solar system, so I can better understand what is taking place when power is recieved and used by all the systems equipment parts etc.

    Sorry for the dumb questions etc.

    Thanks again,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    Asking questions is a good thing - especially if it helps you avoid Icarus' "ready, fire, aim" syndrome.

    That 60a ProgDyn converter/charger might be too big (too many amps) for charging just a single trolling motor battery. Might be too big for even a pair of them really...

    Check the specs on the batteries to see what is the max charge rate they can accept.
  • NvreloaderNvreloader Solar Expert Posts: 71 ✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused
    dwh wrote: »
    Asking questions is a good thing - especially if it helps you avoid Icarus' "ready, fire, aim" syndrome. That 60a ProgDyn converter/charger might be too big (too many amps) for charging just a single trolling motor battery. Might be too big for even a pair of them really... Check the specs on the batteries to see what is the max charge rate they can accept.

    DWH
    Thanks,

    I will check and see the spec's on the 12v battery's.

    I have been doing some more very carefull measuring and I can get the 4 battery's (mounted side by side), (instead of end to end) to the minimum cable length of 8'-9' to the invertor installed place. I have 1 more belly panel to remove and check to see what's inside, Maybe shorter length pending?

    I have found a Cold weather RV camping site (Canada), a member there states that he is using a Boot dryer with 300 Watt heater/blower at 5amps p/hr on 12v.

    Is this possible????? I came up with 300w div by 12v = 25 amps??? As I don't know quite how to figure this info, but it sounds like BS to me, what little I know.

    Instead of using 12V AGM battery's (now that I can use the 1-2 12v tounge battey's), I think I can use 4-6v AGM for a better storage/supply system, as compared to the 12v's.

    Thanks again,
    Don
  • dwhdwh Solar Expert Posts: 1,341 ✭✭✭
    Re: Attempting to get my head wrapped around this solar info, very confused

    300w sounds like a lot for a boot dryer. The Peet 12v unit only uses 30w.

    http://www.peetshoedryer.com/product_go.html

    Even the biggest Peet is only 220w and it is 120v only.

    In any case, your math is right. If he were pulling 5a at 120v that would be 600w, and at 12v would be 60w. So he must have his numbers mixed up.


    6v or 12v doesn't really matter. If you use 6's you'll just have to rig them for 12v anyway. All you end up with is more battery interconnects. You'll still have to supply 12v to the inverter and accept 12v from the chargers.
  • BB.BB. Super Moderators, Administrators Posts: 29,321 admin
    Re: Attempting to get my head wrapped around this solar info, very confused
    Nvreloader wrote: »
    I have found a Cold weather RV camping site (Canada), a member there states that he is using a Boot dryer with 300 Watt heater/blower at 5amps p/hr on 12v.

    Is this possible????? I came up with 300w div by 12v = 25 amps??? As I don't know quite how to figure this info, but it sounds like BS to me, what little I know.
    It sort of depends... It is possible that the heater is thermostatically controlled and may be 300 watts when "on"--but only running a 20% duty cycle (for example; on for 12 seconds, off for 48 seconds) or other type of control (self regulating temperature--after it heats up, the resistance increases).

    Without measuring the load over the X hour drying cycle--It is really difficult to guess what the actual energy usage would be (average Watts * X hours to dry boots).

    A Kill-a-Watt meter (for 120 VAC) or a DC Amp*Hour/Watt*Hour meter would be very handy to plan your loads.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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