How-to properly size battery interconnect cables?

Dumbdumbhead
Dumbdumbhead Solar Expert Posts: 28
Hello, I would like to build a very small low amp, low volt DC charging system. I do not intend to use a DC to AC inverter. The system I intend to build is about as simple as it gets. (2) 50W Kyocera panels, a 15 amp charge controller and (2) Trojan 6-volt T-105s in series.

My question is in regards to what size battery interconnect cables to use in between the two T-105 batteries. I figure since I will only be drawing power through 12-volt outlets at 25 amps max, and being that the two Kyocera panels will output nothing close to that that I need not use 2/0 or 4/0 battery interconnects.

Please correct me if I am wrong, but does it not make sense to only use these bigger cable gauges when you are pulling large amperage, for example; using a DC to AC converter? What I have read so far leads me to believe that a considerable amount of the amperage an inverter draws is usually during the initial start up of heavy appliances, i.e. Microwaves, T.V.s and Heaters. If that is the case and I only intend to use my system for smaller 12-volt devices would it not be better to use, say, #2 or #4 light-duty battery interconnect cables?

Tyia

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?

    For a 12 volt system, you have about 1.0 volts of drop before your equipment will shut down for lack of voltage (too much voltage drop)...

    And for charging the battery bank, it would be really good to have about a 0.050 volt maximum drop in the charging path (from charge controller to positive lead through the interconnect to negative and back to the charge controller.

    So, for example, lets look at 50 watts of panels and 6 foot one way trip (round trip would be 12' -- some voltage drop calculators use one way, others round trip):
    • 50 watts / 17.5 volt Vmp = 2.9 amps
    Using a generic voltage drop calculator playing around (by the way, I used 60' to see the 0.05 volt drop I was looking for--i.e., program will report 0.5 volt):
    • 6' of 10 awg cable -> 0.04 volt drop
    That is the charging current---You would make the same sort of calculations for discharge current too--Probably no more than 0.5 volt drop maximum.

    Regarding your batteries--I guess you are looking at making a 225 AH @ 12 volt battery bank. Rate of charge will be:
    • 2.9 amps / 225 AH = 0.013 = 1.3%
    That is almost a trickle charger (typically 1% or less) and will just barely keep up with the self discharge of that sized battery bank (especially as the batteries age). And with that level of charging current--you almost don't even need a charge controller.

    Having that large of bank with that small of panel really only makes sense if you have an alternative means of charging (genset, utility power, etc.).

    Do you need such a large battery bank (i.e., high surge current)--or are you just looking for a bunch of days of operation without much charging?

    Otherwise, I would suggest a much smaller battery bank and/or more solar panels (usually, somewhere around 5% to 13% rate of charge.

    And if you need such a large battery bank--Perhaps you should look at AGM type batteries... They have less self discharge and will work somewhat better with a smaller solar array (but AGM batteries are ~2x as expensive).

    The problem with Lead Acid batteries is that they tend to sulphate (lead sulfate crystallizes and no longer will charge/discharge--costing battery capacity) if the batteries set below ~75% state of charge for days/weeks/etc...

    Also, battery banks tend to have shorter life if you deep cycle them below 50% state of charge.

    But, it really depends on your needs (weekend cabin, remote data capture site, backup power at home for a computer, etc.; a lot of Watt*Hours or a small amount of Watt*Hours, etc.) as to what you changes you may wish to make to have a system that better meets your requirements.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?

    Rats! I did not realize how poor my intended setup was for my needs. Thanks for the reply btw. I have a very small 17' travel trailer that I would like to retrofit with a solar array. Just enough to supply my daily needs as I will be boondocking almost 99% of the time. I'm looking to avoid the cost of camp space rent and would prefer to travel in some rather remote areas so the self-generating power is a must. The only caveat is that space is at a premium on my roof and pulling big PV panels in and out of the back of my pickup is none too attractive either.

    My main power needs are to power two 17" notebook PCs for at least 8 hours a day and a Cradlepoint CTR500 wireless router for 8 hours as well. As far as television goes we intend to power that via a Yamaha EF2400is generator. The EF2400 will also act as a battery charger when need be, we'd prefer to generate our power via solar rather than start up a noisy,inconvenient generator. So...back to the drawing board I guess.

    I was also toying with the idea of a single Trojan 8D group battery. Again, space is at a premium but we could put the 8D in place of the 2 T-105s we originally intended to use.

    I figure our roof has space for 160Watts of panels max, and that is with best wishes. I could possibly fit one 100Watt and one 60Watt and connect them together. So, if I understand you right BB, you recommend an inverter right? I was just scared that during the conversion from DC to AC there would be a significant loss of power.

    Thanks for helping a newbie ;)
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?

    I usually don't like to cut and past generic replies--but sometimes it saves my fingers and gives you a bunch of information in one spot:
    BB. wrote: »
    Our general suggestion for getting into solar PV electricity:
    1. Conservation--Reduce your power needs by changing to LED/CFL lighting, Energy Star Appliances (computer, TV, etc.), and just turning things off. For AC devices--get a Kill-A-Watt meter to measure their draw.
    2. Know your loads--You need to measure your loads... Watts*Hours (average power * time) or Amps*Hours (for 12 volt / DC loads). Average usage per day and by season (more sun in summer, less in winter -- same for PV power). This is where you set your expectations for your solar power system. Generating the solar power is expensive (~$1.00 TO $2.00+ per kWhr vs $0.10 per kWhr for utility power).
    3. Design the System--This part is pretty straight forward. Define your location, season(s) of use, mounting of panels (fixed, flat or tilt, how much space, etc.). Generator backup power, battery monitoring equipment, how much you want to spend (range of solar panels, charge controllers, inverter, battery types, battery monitor, etc.).
    Here are some frequently asked questions that will help you with the understanding the basic issues:

    All About Charge Controllers
    Read this page about power tracking controllers
    All About Inverters
    Choosing an inverter for water pumping
    Deep Cycle Battery FAQ
    Solar Radiation Tables for US
    PV Watts--Simple Solar Power Calculator Program (use Derating=0.52 for off-grid systems)
    For 12 Volt & RV Systems - HandyBob's long discussion and rant is about 99% right on how to make RV and similar 12 volt systems work correctly. One of the few "non NAWS" articles that we recommend.

    Here is a nice thread with video from Kevin in Calgary Canada that shows designing and installing solar PV in a small RV trailer.

    Our host is Northern Arizona Wind & Sun (Flagstaff Az) and they have a webstore with a good selection of components to build your own solar system. You do not have to purchase from them--but it is a handy place to find reliable products at reasonable prices to layout your system.

    If you have questions about those products, or others from different vendors--please ask. We are all volunteers here with no connection to NAWS (except for Windsun, the Admin from NAWS) and are happy to help.

    There are lots of options out there--but understanding your loads and having enough solar panels to meet the requirements is critical--or you will end up just having to us a small Honda eu1000i or equivalent every few days to make up for too small of solar panels.

    I have seen people mount solar panels on the side of their RV's--And they can tilt them up/out like an awning to better capture the sun.

    Just to get some round numbers...:
    640 WH = 2x 40 watts * 8 hours for laptop computers
    240 WH = 30 watts * 8 hours sat modem
    ==============================
    880 WH per day

    Using PV Watts, assuming Tuscon, 1 kW (round number array), 0.52 tilted to latitude:
    "Station Identification"
    "City:","Tucson"
    "State:","Arizona"
    "Lat (deg N):", 32.12
    "Long (deg W):", 110.93
    "Elev (m): ", 779
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 32.1"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:"," 8.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 5.70, 85, 7.23
    2, 6.11, 80, 6.80
    3, 7.03, 103, 8.76
    4, 7.50, 104, 8.84
    5, 7.29, 100, 8.50
    6, 7.15, 94, 7.99
    7, 6.44, 87, 7.40
    8, 6.85, 93, 7.91
    9, 7.06, 95, 8.07
    10, 6.72, 96, 8.16
    11, 5.99, 86, 7.31
    12, 5.27, 80, 6.80
    "Year", 6.59, 1105, 93.92

    Assume that you are year round camping... Minimum month is December of 80 kWH per month per 1,000 watts of solar panels:
    • 80 kWh per month / 31 days per month = 2.58 kKWH per day = 2,580 WH per day per 1,000 watts of panels
    • 880 watts / 2,580 watts per 1,000 watts of panels = 341 watts of solar panels minimum
    These are just guesses at your daily load--you need to measure (and conserve) to get real numbers.

    Battery bank sizing--1-3 days of backup (no sun) power typically... Use 2 days with 50% maximum discharge (for longer battery life):
    • 880 Watts * 1/12 volt battery * 1/0.85 inverter eff * 2 days * 1/0.50 max discharge = 345 AH @ 12 volts
    That is a pretty big battery for a small travel trailer--And I would suggest going down to 1 day of "no sun" and use a backup genset when needed (or turn of the equipment).

    That would get you down to a ~173 AH battery bank (not far from your 225 AH bank).

    For charging a battery bank, usually 5% to 13% rate of charge. Using your 223 AH battery bank:
    • 225 AH * 14.5 volts charging * 1/0.77 derating * 0.05 rate of charge = 212 watt minimum
    • 225 AH * 14.5 volts charging * 1/0.77 derating * 0.10 rate of charge = 424 Watt Nominal large array
    • 225 AH * 14.5 volts charging * 1/0.77 derating * 0.13 rate of charge =551 watts maximum cost effective array
    So, we are looking at ~341 watt to ~551 watt solar array for my mythical setup.

    If you only camp during summer--you get more sun, so you can use less minimum solar panels.

    If you power your loads during the day (sun up), you might be able to reduce the battery capacity because you do not need much power at night.

    I do like to recommend a small AC inverter (like the MorningStar 12 volt 300 watt pure sine wave inverter). Trying to hook up 12 volts to a bunch of adapters does get to be a pain--plus the voltage range of 10.5 to 15.5 volts of a solar RE power system can blow the "typical" car 12 volt converters. And it makes wiring easier (120 VAC vs 12 VDC--wiring handles only 1/10th the current).

    I forgot--do you have a kill-a-watt or equivalent AC kWH meter?

    Anyway, I will stop typing here and let you ask your questions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?

    BB, I really appreciate the time you are taking out to explain this stuff to me. I'll keep it short and then do some more research this week and get back to you with a "revised" plan of action.

    First, I have the Yamaha gen. So I am not going to ever be up the creek without a paddle. I will find a compromise though so I do not have to rely on this generator. It just defeats the whole purpose of ecology and convenience if I have to rely on a genset to make up for a poorly configured solar array. So...that's not an option.

    I will measure every conceivable inch of my trailers roof, not that it will make non-existence space appear that wasn't there beforehand but perhaps I can squeeze one more panel in up there.

    I would be lying though if I did not say that the amount of power generated with today's current solar technology is a bit disappointing. I'm sure if I had a million bucks I could find the perfect solar solution but I don't and it appears that it takes a considerable amount of panels and space to generate the desired wattage I am looking for. I am not ready to abandoned the idea yet.

    As far as mounting solutions, the side mount as you eluded to, well, I am a paranoid individual and the idea of showing off my bling-bling on the side of my trailer is probably going to give me ulcers. I'm not poor but I'm not rich either and I know there are a great many elves out there that like to walk off with expensive equipment, if not the entire trailer itself :) so...the roof is "thee" place. Out of sight out of mind. I hate the fact we live in a world where we have to psychologically stress about thievery but we do, and it is rampant. It might not be so bad if I were planning on going on weekender trips but I will be traveling the States and places like Cali are not exactly known for its lack of property theft.

    Now, the battery bank issue, that is an issue of limited space as well. I can fit a Trojan 8D AGM battery on the tongue of the trailer and I really liked the point you hit on that I wasn't sharply aware of, and that is the issue of self discharge. I think the AGM is the way to go. Yeah it is a lot heavier and more expensive but it is less maintenance roughly the same AH capacity as the two 6-volts in series. So the Trojan 8D it is.

    I will get the Morningstar 300W DC-AC inverter. You are completely right, do I really want to string my trailer with a million 12-volt outlets. And then there is the issue of 12-volt voltage drop. low volt 12-volt systems require too short of runs. If I had a 24-volt system maybe, but I don't. So a small inverter it is.

    Now it is just about the panels. I will try to squeeze about 200-266Watts up there. I am going to have to get creative. Avoiding shadows from the A/C and vents is going to be a bi**h! Plus there's the issue of weight carrying capacity, not sure what my little 17' marine fiberglass trailer's roof can carry but we are going to find out.

    Alright, that should be enough for today. It's nice there are people like you out there BB. Thank you for all the time you devoted to answering my questions.
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?
    .... As far as television goes we intend to power that via a Yamaha EF2400is generator. The EF2400 will also act as a battery charger when need be, we'd prefer to generate our power via solar rather than start up a noisy,inconvenient generator. So...back to the drawing board I guess.

    use the generator to power a battery charger, the DC output of gensets is very low for recharging a large battery
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?
    mike90045 wrote: »
    use the generator to power a battery charger, the DC output of gensets is very low for recharging a large battery

    Mike, I have a Ctek Multi US 7002 8-stage smart charger. Do you think it would be sufficient to plug it into the Yamaha EF2400is generator and let the Ctek 7002 charge the batteries or 8D battery in this case? I know from experience that when I charge even my auto batteries, in the 80Ah range it takes hours to charge the battery so I am unsure how it would work out trying to charge a 230Ah battery such as the Trojan 8D battery with the Ctek on top of being plugged into the generator. Sounds unrealistic. The Ctek charger seems to charge at very low amps, 7amps max I believe. Paint dries faster. It's a great charger but I am not sure it will work out for my traveling purposes.

    Thanks
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?

    You are very welcome--We all started in pretty much the same places and made our mistake$ too.

    Computers/digital equipment running 8-12 hours per day is a real energy hog. Even for the "Grid".

    All I can add is look for the smallest/most power efficient laptops that will meet your needs you can find... It is possible to smaller PC's that are done to the 8 watt average power usage... And as you can see, solar arrays are very inefficient at collecting energy (unless you want to spend 100x the cost for space rated panels that are ~2x as efficient).

    Again--I made a whole bunch of guesses and they may be close or far away from your power needs. Also, your location and seasons of camping, and a whole bunch of details I did not go into...

    In the end, I think the numbers are close enough for financial planning to see if you are even close to meeting your power needs.

    And, look at a Honda eu1000i genset... They are small and light--and probably will match your charging needs for the battery bank to minimize fuel usage. I am a big fan of matching gensets/AC chargers to the needed loads. Many times, people use larger gensets and use 2-3x as much fuel because the big gensets are lightly loaded. If you can load your genset to >50% of rated output--your fuel is much more efficiently burned for electricity.

    In the end, you may end up with two gensets or two inverters--A small one for
    battery charger and small loads--The big guys for running your A/C, tools, emergency backup, etc.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?

    I believe in sizing the genset and battery charger to the size of the battery bank--Again in the 5%-13% (although, you can go as high as 25-30% of AH rating).

    A large genset with a small battery charger (2,400 watt generator and 105 watt battery charger) is just burning a hole in you wallet regarding fuel consumption.

    If you are looking at a 255 amp 12 volt battery (especially AGM) you could go with a 10-20% AC charger pretty easily.
    • 255 AH * 14.5 volts charging * 0.10 rate of charge * 1/0.80 charger eff * 1/0.6 Power Factor = 770 VA
    • 255 AH * 14.5 volts charging * 0.20 rate of charge * 1/0.80 charger eff * 1/0.6 Power Factor = 1,540 VA
    • 255 AH * 0.20 Rate of Charge = ~61 amp battery charger
    So, if you are going to use just the Yamaha 2400--You could run a 12 volt 60 - 80 amp AC charger pretty easy on there. Something like this would work well:
    wind-sun_2155_22704694Iota DLS-75: 12 volt 75 amp regulated battery charger
    Price: $321.00


    If fuel is a big issue for you--You could back down to a smaller genset and charger.... SteveK went through a whole bunch of research to find the "optimum" charger for his Honda eu2000i generator (1,600 watt). It is a great thread to read if you wan to learn the electrical details behind all of the rules of thumb we use here.

    Question about battery charger selection with EU2000 generator.

    If you are not a "techie" and into the details--It may not be the thread for you.;)

    To use the generator in an optimum manner--typically we recommend charging your battery bank first thing in the morning with the genset and after the bank is 80-90% full and the battery charger is cutting back on charging current--shut down the genset and let the solar charge the last 10-20%.

    You normally do not want the generator to charge the last 10-20% because the current accepted by the battery is way reduced and you are just wasting fuel running the AC battery charger.

    Also, a Battery Monitor is a great tool--especially for AGM's which are sealed and you cannot monitor their specific gravity with a hydrometer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?

    Great advice, thank you. That Iota charger will be far better for my needs. I love the idea of charging the batteries up to 80% with the gen and then letting the solar panels do the job of trickle charge babysitting. Any idea why you choose the morning to charge the batteries? Or is it just as good of time as any? I know the temps of the batteries play a part in their performance, I read somewhere that batteries are like people, if the weather feels comfortable to you then the batteries probably feel comfortable too.

    Two last ideas, First idea, I was looking at the Sky Blue SB1524iX and it has LVD technology on it. I was wondering whether that would be helpful so that I didn't run the battery bank down to harmful levels. It will automatically disconnect load devices correct?

    And lastly, When you said I can use the genset and Iota battery charger to charge the batteries to 80% can I charge the batteries while they are connected to other equipment? i.e. the solar charger, battery monitor etc... Is there a risk of sending a harmful spike or surge to these devices when I charge it with the gen and Iota battery charger? Should I be looking for a disconnect switch or something?

    Ciao!
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?
    Great advice, thank you. That Iota charger will be far better for my needs. I love the idea of charging the batteries up to 80% with the gen and then letting the solar panels do the job of trickle charge babysitting. Any idea why you choose the morning to charge the batteries? Or is it just as good of time as any? I know the temps of the batteries play a part in their performance, I read somewhere that batteries are like people, if the weather feels comfortable to you then the batteries probably feel comfortable too.
    Pretty much--Batteries are typically rated around 77F / 25C... A good rule of thumb--if the temperature goes up by 10C (18F), the life will be cut by 1/2. If the time goes up by 20C, the life will be cut by 1/2*1/2=1/4... This is only for the time the battery is above 25C.

    And conversely, if the battery is 10C lower than 25C, its service life will be 2x longer...

    Note, this is battery "life"--not capacity. Because of the Lead Acid chemistry, hotter batteries can supply/store more energy than cold batteries. And batteries near freezing start loosing substantial amount of output AH.

    Why AM? For most people (perhaps not you), they charge during the day and draw down at night--In the morning, if the battery is below ~75% state of charge, sulphates begin to harden--so you want to get the battery recharged above ~75% state of charge quickly (genset + AC charger is usually > solar array). You want your batteries to spend as little time as praticable below 75% state of charge.

    Second, you want to run the genset at its most fuel efficient... That is when the batteries are discharged and the sun is still not full up shining on the solar panels.

    Let the genset/AC charger dump "lots" (i.e., >50% generator capacity) into the battery bank for 1) fuel efficient charging and 2) get above 75% state of charge.

    Now--You don't have to run only the AC charger to get the 50% load on the genset--you can run the computers, coffee maker, microwave, hand tools, etc. on the genset too and get that work out of the way in the morning. By mid-morning, the batteries are hopefully in the 80-90% state of charge, and you have the solar panels to "taper" charge the batteries the rest of the way (and support your day time loads in your case).

    A couple good things to read:

    Deep Cycle Battery FAQ

    www.batteryfaq.org

    "Know your enemy"--Or "know your friend"--Batteries are fickle that way. ;)
    Two last ideas, First idea, I was looking at the Sky Blue SB1524iX and it has LVD technology on it. I was wondering whether that would be helpful so that I didn't run the battery bank down to harmful levels. It will automatically disconnect load devices correct?
    The Blue Sky family of controllers work fine but are getting long in the tooth... You might also want to look at some new MPPT type models.

    Low Voltage Disconnect is typically set to a voltage level (10.5 volts, 11.5 volts, etc.). Voltage of a lead acid battery under load (or charging) does not really represent the state of charge at all... So, it is not a good way to make / automate power systems.

    Also, LVD's are typically lower current circuits (8-10 amps or so)--Any good sized AC inverter or larger DC load is too much for these LVD output.
    And lastly, When you said I can use the genset and Iota battery charger to charge the batteries to 80% can I charge the batteries while they are connected to other equipment? i.e. the solar charger, battery monitor etc... Is there a risk of sending a harmful spike or surge to these devices when I charge it with the gen and Iota battery charger? Should I be looking for a disconnect switch or something?
    No and yes...

    The charger device we usually list here are good quality and should not "lose control" if properly connected to the right sized battery bank (a large charger on a small battery bank--all bets are off).

    However, many 12 volts DC adapters are designed for use on a car... Assuming around 13.8 to 14.2 volts. Many devices will loose power below 13.8 volts (i.e., transmitters) or draw more current (power=volts*amps, if volts go down, amps goes up)... Running them at 11.5 vdc (or less) is perfectly normal, but that can cause ~20% or more current draw--overheating the inexpensive adapters.

    The other issue is when charging... The typical charging voltage can be in the 14.5 to 14.8 volt range and equalization in the 15-16 volt range--which can over-voltage these adapters.

    That is another reason I like AC inverters--The good ones are designed for the wider range of off-grid battery systems and will either work fine or shut down safely if the battery voltage goes out of specifications.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?

    Alright, here is my revised setup.

    (2) NOCO HM318BK Group 24-31 Snap-Top Battery Box

    (2) Trojan Group 31-AGM 12V cycling agm batteries

    (2) Kyocera KC50T with J-Box Solar Panel

    (1) Morningstar SunSaver 15 Amp MPPT Solar Charge Controller

    (1) Morningstar Remote Digital Meter for SunSaver MPPT and SureSine inverter

    (1) Morningstar 300 Watt Sine Wave Inverter

    (1) Iota Engineering DLS-45 45 Amp, 12 Volt Regulated Battery Charger

    (1) Yamaha EF1000iS generator

    I now realize that I am going to have to use the generator as a full-time partner in this type of setup. I can't really avoid it, so I will strike a compromise by getting the smaller 1000 gen. over the 2400 as fuel cost and efficiency is a concern for me. Thanks Bill for all your advice. I suspect if I had went ahead and bought the items I had planned on buying I would have been sorry for it. Please let me know what you think about this setup, at your convenience of course, no rush.

    Please remember that my main desire is to run the two notebooks for a few hours a day along with the Cradlepoint router. Unfortunately buying 2 new ultra-efficient notebooks isn't feasible at this moment, also my eyesight is rather poor so the 17" notebook has to stay, no choice as my eyes are already straining while using the 17".

    Thanks a million
  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?
    BB. wrote: »
    I forgot--do you have a kill-a-watt or equivalent AC kWH meter

    Yep, in the mail and on the way. I purchased the P3 International P4400 Kill A Watt Electricity Usage Monitor. When it gets here I will have a chance to run the two notebooks and the Cradlepoint wireless router on it to determine my exact Wh needs.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?
    (2) Trojan Group 31-AGM 12V cycling agm batteries 100 AH each

    (2) Kyocera KC50T with J-Box Solar Panel 50 watt panels

    (1) Morningstar SunSaver 15 Amp MPPT Solar Charge Controller very nice--may be overkill

    (1) Morningstar Remote Digital Meter for SunSaver MPPT and SureSine inverter look at getting a Battery Monitor instead (or in addition)--BM may be a better investment (Trimetric or better).

    (1) Morningstar 300 Watt Sine Wave Inverter very nice inverter

    (1) Iota Engineering DLS-45 45 Amp, 12 Volt Regulated Battery Charger probably too large for Yamaha EF1000iS genset--Look more at 20-30 amp maximum.

    (1) Yamaha EF1000iS generator should be nice--but Iota charges are not power factor corrected. They take ~1/0.6pf = 1.67x the current vs a PF corrected supply and will probably overwhelm the genset. Others may have better information than I.

    I now realize that I am going to have to use the generator as a full-time partner in this type of setup. I can't really avoid it, so I will strike a compromise by getting the smaller 1000 gen. over the 2400 as fuel cost and efficiency is a concern for me. Thanks Bill for all your advice. I suspect if I had went ahead and bought the items I had planned on buying I would have been sorry for it. Please let me know what you think about this setup, at your convenience of course, no rush.

    Yes, at this point a pair of 50 watt panels will not supply very much charging current:
    • 2x 50 watts * 0.77 derating * 1/14.5 volts = 5.31 amps
    That is around the minimum charging current we would recommend for 1x of your 100 AH AGM batteries.

    The MorningStar 15 amp MPPT controller is very nice--but may be overkill here unless you plan on adding more panels to get upwards of:
    • 15 amps * 14.5 volts * 1/0.77 derating = 282 watts of solar panels
    Unless you will be out in very cold weather (sub freezing) and/or mounting the panels a long way away (stake to ground 50' away from RV)--A cheaper PWM controller may be "good enough" for now.
    Please remember that my main desire is to run the two notebooks for a few hours a day along with the Cradlepoint router. Unfortunately buying 2 new ultra-efficient notebooks isn't feasible at this moment, also my eyesight is rather poor so the 17" notebook has to stay, no choice as my eyes are already straining while using the 17".

    Yea--we harp on conservation--but recognize that power usage is a very personal matter. We don't argue with choices--just offer facts and our opinions the best we can.

    Looking at your power needs will help a lot in sizing the system. At this point, I would probably suggest that you get only 1x AGM battery for now and simply run the genset every morning (when needed). Unless your measured loads are high than we think or you really need a day or two of silence.

    The total genset runtime will be the same--just 2x the batteries and 2x longer between charging mean running the genset 2x longer every two days...

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?

    I would verify with IOTA, what the power factor on the charger is, I know mine is not good (measures .67) , and that has to be accounted for when sizing the generator.

    I use a VEC1093 12V Charger (search for it on Amazon) - it's power factor corrected, and can do 40A into the batteries.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: How-to properly size battery interconnect cables?

    Mike,

    What are the Watt and VA readings for that Vector Charger... If it is low enough, it should a good unit for the Yamaha 1000i and the Honda eu1000i (900 watt).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?
    BB. wrote: »
    Mike,

    What are the Watt and VA readings for that Vector Charger... If it is low enough, it should a good unit for the Yamaha 1000i and the Honda eu1000i (900 watt).

    -Bill

    Power Factor reads on K-a-W at .94, @ about 15A. I don't have a dead battery to test it on for full 40A charge, but I'll look into it this weekend, and record #s' from it.
    ( VEC1093 12V Charger )
    Mike
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?
    mike90045 wrote: »
    I would verify with IOTA, what the power factor on the charger is, I know mine is not good (measures .67) , and that has to be accounted for when sizing the generator.

    I use a VEC1093 12V Charger (search for it on Amazon) - it's power factor corrected, and can do 40A into the batteries.

    Hi Mike, I searched the internet for the VEC1093DBD charger you were talking about, It seems good for my purpose in terms of its fast charge rate but from reading the reviews on Amazon it appears to have some issues, some people stated that they had problems with the fan going out. I don't want to dismiss it on a few negative reviews but it does make me leery.

    To be honest I have no idea about "power factor" of the battery charger. I guess that is yet another thing I need to learn about :roll:

    I will need a high amperage battery charger though, no way around it. Can you give me a very brief tutorial on how the "power factor" of a battery charger plays and part in what generator you pair with it?

    Thanks a lot
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?

    power factor

    I'll pass that onto wikipedia
    http://en.wikipedia.org/wiki/Power_factor

    Basics: with AC, sometimes you can't get full power because the current and voltage have a phase shift with each other and don't align well. There are complex circuits to prevent this from happening. (power factor correction)
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?
    mike90045 wrote: »
    power factor

    I'll pass that onto wikipedia
    http://en.wikipedia.org/wiki/Power_factor

    Basics: with AC, sometimes you can't get full power because the current and voltage have a phase shift with each other and don't align well. There are complex circuits to prevent this from happening. (power factor correction)

    I read the Wiki link, a bit over my head but what I think I took away from it is that the delivery of power is imperfect and thus must be "corrected" through P.F.C. in order to see the full potential of the "real power" supplied, not apparent power?

    So when you said your Iota battery charger had a P.F.C. of only .67 that means it has a P.F.C. of 67% correct? And being that your VEC1093 charger has a purported P.F.C. of .94 that would make it 27% more P.F. efficient than the Iota model thus shortening battery charging time? I might be way off the mark, please correct me if I am.

    Btw, is your VEC1093 charger a Black & Decker model?

    Thanks
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?

    You have it very close. It's not the battery side that is at issue, it's the generator side. The VEC1093 is more efficient at using power from the generator, the Iota, needs a 30% larger generator, because it's less efficient (poor power factor).
    When you plug into the "grid" this is not an issue, but when useing a generator, it becomes important, hence the "is the generator large enough" thread.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • Dumbdumbhead
    Dumbdumbhead Solar Expert Posts: 28
    Re: How-to properly size battery interconnect cables?
    mike90045 wrote: »
    You have it very close. It's not the battery side that is at issue, it's the generator side. The VEC1093 is more efficient at using power from the generator, the Iota, needs a 30% larger generator, because it's less efficient (poor power factor).
    When you plug into the "grid" this is not an issue, but when using a generator, it becomes important, hence the "is the generator large enough" thread.

    Great, so do you think the Yamaha EF1000is will be able to handle the VEC1093 battery charger? How much load would the Yamaha EF1000is be under percentage wise when running the VEC1093? BB said a 50% load is perfect, that way I am not wasting gas running a small load on too large of a generator.

    One other question I have, how did you determine the P.F.C. of your units? Do you have a P.F.C. meter of some type? I searched both Iota's, Vector's and Black & Decker's charger manuals and could not find any reference to P.F.C..
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: How-to properly size battery interconnect cables?

    I used a kill-a-watt meter to measure the iota:
    1030w 11.9A .67 PF

    The Vector, either had a sticker on it, or I measured it some time ago. I'll load it down and see what the k-a-w measures.
    15V @ 40A = 600W so it's not much of a load for a 1KW generator, and with a good PF, should not be over 700W. As soon as the battery starts charging up, the 40A changes to 35A to 30A, and the genset starts slowing down, as it doesn't need full power anymore.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,