Small system need advice

System

Thanks, Niel, for the response to my last post. The information throughout the forum is terrific.
The more I learn about solar the more I need to learn and its nice to learn from folks with experience.

The Oregon Desert property I will soon be retiring on is 35 miles from the nearest power so the grid is not and never will be a factor. The closest "town" is 53 miles of rough road away and I will be isolated from time to time in the winter so solar to me is very important.

I will be running almost exclusively 12 volt on my appliances: water pump, small fluorescent lights, laptop, cell phone charger, DVD, CB, etc. with the occasional use of an inverter. The fridg., stove, oven and hot water heater are propane and heating is by wood stove. Much of my heated water will be from thermal solar.

My power needs are simple and my calculations show that at the most I will require is 32 amp hours a day with 8 luxury hours thrown in is 40 amp hours. Unfortunately the most need will be in the winter. (Less sun and more time inside.)

I will be able to boost the amount of amp hours in my battery bank when I run the generator
for the washer/dryer, power tools, etc. but do not want to run them much just for re-charging the batteries. How will this affect the batteries if I don't completely re-charge them or just throw partial charges into them when running the generator for short periods of time?

I have three 12 amp battery chargers that I plan on plugging into the generator and clipping to the batteries while the generator is running. Is this wise?

Is it OK to charge them with the generator at the same time the solar is charging them?

I calculated this system based on the manufacturer's specs. and no knowledge of peak solar radiation.

The latitude is 43.58, with 11 inches of precipitation, and over 300 days of sun per year.

This is what I have purchased:

Three 45 watt panels
four top quality 120 amp hour RV/Marine batteries
A 10 amp sunsaver controller
800 watt inverter (overkill?)
5 watt panel and separate battery for the 13 mA electric fence charger. (open range)
A 4500 watt and 2200 watt generator
quality hydrometer and digital volt meter

In reading through the forum it looks like three 45 watt panels may not be sufficient. Do you think I need more panels?

Since I plan on installing the panels on the water tower I will be constructing, and looking at the solar radiation chart, it would not be too difficult to mount them on a one or even two axis frame that I could rotate manually as the seasons change. Would this make a significant difference?

Any suggestions or recommendations on my system will be greatly appreciated.

Thanks,

Arch

crewzer

Re: Small system need advice

43.58 N latitude? Anywhere near Burns, OR? Here's the NREL solar insolation data for that area:

http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/94185.txt

HTH,
Jim / crewzer

BB.

Re: Small system need advice

First, you can take a look at this solar data and estimate the amount of sun (solar) energy you can collect between flat plate fixed (at latitude and +/- latitude) and for 1 or 2 axis tracking. Find the town/location closes to your place (or at least, similar weather).

http://rredc.nrel.gov/solar/pubs/redbook/

If you know of somebody with a year's worth of solar data near your cabin that you can relate the above solar data to--that will help you ensure that you adjust the numbers for your area.

Looking at Pendleton Oregon (guessing) as being in Eastern Mid-Oregon, you solar radiation runs (30 year average) around 6 kWhrs/day-sq.meter (mid summer) to as low as 2 kWhrs/day-sq.meter (in winter). Roughly, this is equivalent to 6 hours of sun and 2 hours of sun per day.

For your 3x 45 watt panels (135 watts total), you probably will see, roughly 120 watts maximum on a bright sunny (and cool) day. In theory, you can expect somewhere around 270 watt hours (or 270whr/12 volts = 22.5 amp*hours in winter... Assuming that you are using standard solar charger and lead acid storage batteries, you are somewhere round 80% efficient, which gives you an effective average winter output of 22.5amphour * 0.80= 18 amp*hours (in the summer, it would be approximately 3x or 54 amps*hours per day).

Given that you want ~40 amp*hours per day, you would need to at least double your current array (assuming that it is a fixed array). A one or two axis tracker does not seem to help much (maybe 10% or so) because there is so little sun at that time of year (weather/clouds too???). My own array (last year was my first winter with Grid Tied array) was even worst than predicted because of heavier than normal rain and clouds).

Second, I would humbly suggest that you permanently wire the batteries into bank(s) and permanently attach the chargers (solar, wind, generator driven). the last thing you want is to create sparks (light-off the hydrogen gas generated during charging) or accidentally short something, or otherwise go through several times a week of moving clamps/cleaning corrosion, etc...

And not to get too wordy here--A gallon of gasoline will generate, roughly, 416 amp*hours (5,000 to 5,500 watts rough estimate for a Honda eu2000i generator)--so, even though you don't like the noise, pollution, and fuel costs, there is certainly a trade-off between solar in winter vs generator time. I would suggest that you also try to size the battery bank to supply 3 days of typical load (no sun) and using no more than 50% of your battery capacity (to help the batteries have a long and productive life).

The above numbers are sort of conservative--but with solar and electrical loads, it is easy to be off by 50% for your particular conditions and current weather. You could easily double your solar panel size and not be terribly unhappy (more costs upfront, less generator time over the years).

Regarding the inverters, there is a whole 'nother set of issues... If this is your home, you will want sine wave rather than "modified sine wave" inverter(s) for your cabin. However, sine wave types cost probably 5x (or more) than the cheap and dirty modified sine wave units--but they are needed if you will be running electric motors or other expensive appliances. And you can easily have a huge inverter that a small battery bank could never really run at full load (without damaging the batteries).

Anyway, I will stop here and let you ask/direct your questions along the line you are interested in rather than just going on and on...

Sounds like a nice place to retire!
-Bill

niel

Re: Small system need advice

arch,
in general i agree with bb, but if you get snows or heavy winds don't even consider a tracking system. many would rather just buy more pvs than a tracker. wind generation is something to consider if you do get good winds. even if you don't it could contribute more during those vital winter months when solar isn't as available. there are cloudy periods, low solar radiation strength, shorter full sun hours available, and the one thing many forget about is snow buildup on the pvs. snow blocks sunlight, but with adjustable mounts the winter angle can be increased to allow better aiming towards the strongest elevation for sunlight which is now closer to the horizon(guessing at 20 degrees off of the horizon at the highest during the winter solstice and pv nearing a vertical angle off of the ground at around 60-70 degrees) and allowing for less sticking of the snows by allowing it to slide off easier.
as to what you've got:
*Three 45 watt panels (i recommend you will need at least 5% of the battery capacity to charge the batteries so that is around 23amps from the pvs with a 3% minimum giving 14.4amps from the pvs and no loads on. more with loads and are equal to the load's draw. roughly 10% of the battery capacity you shouldn't exceed or 48amps. all of this being measured realtime and not pv's max specs like stc ratings.)
*four top quality 120 amp hour RV/Marine batteries (will be fine if maintained and charges/discharges watched for proper operations)
*A 10 amp sunsaver controller (will be fine for now, but more ss10s can be paralleled for adding more pvs when it exceeds the safe capacity levels of the one ss10. do note the inputs to all of the ss10s can't be common to all pvs as each controller will have its own bank of pvs driving it. the controller outputs to the batteries can be in common or paralleled with each other.)
*800 watt inverter (overkill?) (probably is overkill and some good sinewave inverters have built-in chargers too, but mod sinewave i don't recommend for anything with electric motors or little walwort adapters. no air conditioners or electric heaters shall be used.)
*5 watt panel and separate battery for the 13 mA electric fence charger.  (open range)  (i hope it's enough to keep your fence running especially during the winter months and you will have to wipe it clean of snow if need be so it shouldn't be difficult to access.)
*A 4500 watt and 2200 watt generator (this is good for sure power as long as you have a supply of gas.)
*quality hydrometer and digital volt meter (this is good for rountine checkups on battery conditions. the voltmeter you will find invalueable though. this even gives rough battery states of charge at a glance and you'll come to know what i'm talking about. do also be sure to have pure distilled water only for adding to the cells of the batteries. make sure the water does not get contaminated by the container it's held in or delivered into the cells with.)

there's so much that can be said, but this should be sufficient for now.

BB.

Re: Small system need advice

Arch,

And here I went on and on, and forgot to answer a few of your questions that you asked... The shame...

Yes, it is OK to charge the batteries with both solar and a generator at the same time... You should look at your battery specifications for max charge rate (and have thermal controlled chargers) to prevent thermal runaway. Some types of battery types accept high charge rates better than others. With a generator and a smaller battery bank (especially if there is not good cooling/air circulation) it could be possible to charge a battery bank too quickly. Somebody here can give you better information than I on the recommend rates (usually, charge rates should be between 1/20 to 1/1 of C--Battery capacity--125 amp*hour 12 volt battery would be C=125, or charge current range of 6 amps to 125 amps--but ideal would probably be C*1/10 to C*1/5 or roughly 12.5 to 25 amps for one battery... If you have 4x 125 amp*hour batteries in parallel, then the current would be 4x greater).

Regarding partial recharging of batteries--from what I have read here, the deeper the discharge, the quicker you should fully recharge the battery--or the thick sulfate layer (that naturally develops as the battery discharges) can harden and reduce the capacity and life of the battery. If I recall correctly, if you accidentally drop well below 50% capacity (discharge), you only have hours or a day to recharge the battery before damage is permanently done--Again, I am not the expert here. I hope that somebody else here can give the "official" explanation.

Lastly, you may wish to look at the following link (shameless plug for the sponsor of this fine wind-sun forum) for battery monitoring systems... Because there are all sorts of issues with battery chemistry that affect charge/voltage--using one of these meters to monitor energy in and out of your battery bank will help you prevent over discharging your batteries and prematurely ending their life.

http://store.solar-electric.com/metersmonitors.html

-Bill

System2

Re: Small system need advice

Thanks for the replies, this information is sure what I was looking for. It really gives me something to sink my teeth into.

Appreciate it.

Arch

crewzer

Re: Small system need advice

Arch,

32 Ah (at 12 V) per day? I estimated ~28 Ah/day just for a laptop in this previous discussion:

http://www.wind-sun.com/smf/index.php?topic=1463.0

Average solar radiation on a south-facing PV array tilted up at ~58.58 degrees (= latitude + 15 degrees) is 2.9 hrs./day in December. Average radiation – even at this tilt angle -- is higher for all other months, although peak array current will be lower due to less than ideal array alignment.

More on solar radiation in your area is available from these sites:

http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/94185.txt
http://solardat.uoregon.edu/

Assuming your requirement of 40 Ah/day and a battery bank coulombic efficiency (Ah out / Ah in) of 90%, you’ll need an array that can produce 40 Ah/day / (90% x 2.9 hrs/day) = 15.4 A. I estimate your three 45 W modules wired in parallel will be good for ~ 8 A, or about ½ of your requirement.

The three 120 Ah batteries wired in parallel will create a battery bank rated at 12 V x 480 Ah. At 40 Ah/day and limiting your discharge to 50%, the bank will provide 480 Ah x 50% / 40 Ah/day = 6 days of autonomy. That’s great!

However, at just 8 A, the charge current from the 45 W x 3 = 135 W array will be just 8 / 480 = ~1.6% of the battery capacity, so the array will probably not be able to recharge the battery bank, even if there’s no load. 5% charge current is a practical minimum capability.

The SunSaver controller is a good basic controller, but it doesn’t offer a battery equalization function nor temperature compensation based on battery temperature. And, at 10 A, it’s just abount maxed out with your present PV array, so adding more modules isn’t really an option with this controller.

As you noted, the 800 W inverter is probably overkill given your planned energy requirements. Similarly, the two generators are likely much larger than you’ll ever need.

So, some suggestions:

1) Double check your projected energy requirement.
2) You can stay with your present system configuration if you buy a Xantrex TC40 battery charger. Assuming 40 Ah/day, you’ll probably need to use it ~once a week or so in the Winter to fully recharge the battery bank while the PV array serves as a trickle charger. The TC40’s 40 A charge current is about ideal for a 480 Ah battery bank, and it includes temperature compensation and flooded-cell battery equalization features. The 2200 W generator will easily handle the TC40’s full load of ~15 V x 40 A / ~80% efficiency = ~750 W.
3) If you want to consider adding more PV modules, you’ll need grow to at least 270 W. The ~16 A charge current should be just enough to be able to recharge the battery bank, but a bank of just 3 batteries (360 Ah) would probably be better. A good full-featured solar controller/charger for a system of this size is the Morningstar ProStar 30 M. Another benefit of the ProStar 30 is that it can handle a 12 V PV array of up to ~500 W, so you’ll still have some additional room for growth.

HTH,
Jim / crewzer

System2

Re: Small system need advice

Thanks again to everyone, its so much better to do it correctly now than get out there and learn the hard way. This is a lot more complex than I thought.

In digesting all of this information, I can see three things that I need to address first.

1. More solar panels
2. A larger controller
3. Replacing my modified sine wave inverter for a sine wave inverter

More panels:

I found locally a used Siemens SP 75, seventy five watt panel yesterday that I can buy for $350.00. It was put in service in October of 1998 and used until about a month ago. On the back it indicated that it is rated at 4.4 amps, open circuit 21.7 V rated at 17.0 V From what I have learned in the forum this should be a 12 volt panel. (?)

The price seems pretty good (?) and the panel looks to be in perfect shape plus I can have it in my hands right now. This would take me from 135 watts to 210 watts and go a long way to making it in those winter months. All I will need then is to pick up another 75 watt panel and I will make the 270 watts minimum needed to make my 40 amp hour per day requirement.

A larger controller:

I went to Northern Arizona Wind and Solar ( this is a great site, concise and easy to navigate)
and drooled over the Morningstar ProStar 30M, this looks like the ideal choice, thanks for the suggestion.

It looks like I will need a shunt too. (?) I'm not sure what a shunt actually does?

Sine wave inverter:

I have tried to go with 12 volt for everything but there are a few 120 volt items that I just can't get around. (my regular computer and photo printer occasionally to transfer and print wildlife photos and the monitor, etc.)

I will be under 300 watts with anything I use that is 120 volt. I looked at the Samlex 300 watt
12 volt sine wave inverter, its more affordable and appears to be what I need. Is this a good choice?

Bill brought up a great point about the trade-off between solar in winter vs. generator time. Since the closest "one gas station town" is a 106 mile round trip on rough road I was thinking
not only about the cost of gas to run the generator but also the cost of the gas in a full size Bronco just to go get it. I thought it would take a lot more gas to charge the batteries with a generator, still nice to be totally independent though.

With one gallon of gas generating roughly 416 amp hours and the need to run the generator once a week for a couple of hours to use the washer/dryer anyway, I can make it through the harshest winter and never deplete my batteries below 50% and the solar will still be doing a lot of the charging. I will be living there full time so this takes a serious load off of my mind.

I'll be throwing 36 amps into the battery bank when charging them with the generators.

Something I'm pretty confused on: I have three 12 amp battery chargers that I intended to plug into the generator and just clip the leads on to the batteries for that once a week or so charging in the winter and then take the clips off until the next time.

Can I run the charging wires directly to the controller and and mix them in with the charging wires from the solar panel? This seems like a much better way to use the 12 amp chargers and would guarantee that I would not overcharge the batteries. Plus no sparks.

As suggested, I checked with the dealer that sold me the batteries and with these specific four batteries in a bank with the 36 amps from the 12 volt chargers plus the charge from the solar panels at the same time I will still be below the maximum acceptable charge so that I do not throw too much into the batteries at once.

Where does the electricity go when the controller decides that the batteries are charged?
It would seem that the chargers are still sending a full load to the controller.

I am very grateful for your time.

Arch

BB.

Re: Small system need advice

Regarding generator to charge the batteries/run washer and other loads...

The numbers I quoted were for the Honda eu2000i running between 25% and 100% load (1,600 watts continuous) using the Honda specs (I have not tested it myself). As long as you are running the eu2000i between 25-200% load, the fuel consumption was pretty linear with Watts out. Obviously, if you use the generator to run a 4 watt nightlight, most of the fuel is going to spin the generator and wasting heat.

So, first, try to plan the loads for optimum power of any generator. A watt meter (or amp meter) connected to the generator will help you monitor your system.

Regarding battery charges from AC mains/generator... Depending on the charger and the generator combination, sometimes the chargers cannot draw near full load from the generator (drops the AC line voltage or other issues). One charger that has had good press here and other places is the IOTA brand charger. Many chargers can output high charger currents with discharged batteries, but quickly ramp down before the battery bank reaches full charge--taking much longer to charge the batteries that it should. IOTA's reputation is that they do a good job of pumping power into the battery bank and tapering off correctly. A simple 12 volt charger may not have the two or three mode charge that is really needed to correctly charge lead acid batteries (and different types of batteries--flooded cell/sealed cell and manufactures required different voltages and float values--or no float at all).

So, first, look at the specs. for your chargers and make sure that they do what you need and expect.

Second, a good charger that charges at high currents will probably have remote sense leads... Basically, you connect the heavy wires somewhere that eventually goes to the battery. The sense leads (+ and -) connect directly to the battery terminals (or as close as practical--through fuses or resistors to prevent shorts) and give the controller a very accurate voltage reading at the batteries. Connecting large chargers far away from the batteries themselves (and mixing with solar and AC chargers) can give the chargers a false battery voltage (and, usually, cut the charge rate because the wiring resistance raises the apparent voltage that the charger sees). This would be the drawback of connecting the solar and AC chargers to the same bus (away from the battery). However, using fuses and/or circuit breakers to protect the wiring and equipment from the very high currents available from any ordinary storage battery is pretty mandatory for safety.

To be honest, unless those are three very good quality battery chargers, I would not expect them to really do a good job of maintaining your battery bank. However, since you already have them, it would not hurt to try them and see how they perform. But I would suggest cutting off the clamps and connecting them close to the battery bus bar--should be through fuses or breakers for safety.

Regarding where does the power go? Each charge controller, Solar or AC, is basically a one-way device. If the battery is discharged (decided by battery temperature, voltage, and charge timing algorithms and charge type desired) the charge controller. The charger will either take power from the supply (Solar Panel or AC) and, to the best of its ability, apply current to the batteries (the Solar Controller will also be limited by the ability of the solar panel to generate current/power).

When the controller(s) decide the battery is charged, they will simply output less (or zero power).

Some solar controllers (and wind too), have the ability to divert the excess power available from the solar panels (or wind generators) to another load (typically a resistive heater). This is not needed for a solar panel (a solar panel with no load is perfectly happy). A wind turbine will typically overspeed in high wind if there is no load (or other speed control like feathering)--So, a diversion load/controller may be needed in the the case of wind turbine.

The shunt? That is just a calibrated power resistor. Typically used where heavy (large) currents need to be measured. They are actually very nice to use in battery systems. Simply V=I*R where R is small and I is large, and resultant V is 10's or 100's of millivolts (depending on shunt rating). You put a Shunt in the battery circuit using short large gauge wire. And then use small gauge wire to a remote mounted volt meter (typically calibrated in millivolts). This saves running large gauge wire to where your meter is located.

-Bill

niel

Re: Small system need advice

be carefull with standard automotive chargers as these are non regulated and sometimes too cheap as i found out. i had a sunsaver 10 with my 6amp battery charger on it. the charger had an internal failure and sent 110vac down to the controller and blew it out instantly. luckily i was there to disconnect it from the batteries as batteries are more resilient, but it's not a good idea to try that for any length of time. there isn't any easy way of protecting against something like that, but you should have fuses for safety and maybe even switches for each charger to prevent arcing when working on the batteries. sometimes you can't put a charger up to a controller as they just won't work at times. in using the chargers straight to the batteries this would be a bulk charge. this accounts for 80% of the charge. after the max voltage level is reached for bulk charging the acceptance charge and a float charge takes it the rest of the way. some just go from bulk to float as well and it'll work, but it takes slightly longer to reach 100% charge. you could use these chargers if they work for now, but try to go for a good iota charger or some other quality charger. naws lists some and you will pay more for them, but you're getting a quality product unlike your cheapo automotive chargers. those automotive chargers could be backups for your good one(s).
i see bb posted while i was so some of this is repeating, but you get the idea. btw a ss10 goes from bulk to acceptance and technically does not float. it just continuously reduces the current at the voltage you select for the bulk charges end. real float charges have smaller voltages.

crewzer

Re: Small system need advice

Arch,

I found locally a used Siemens (Shell Solar, SolarWorld) … SP 75… On the back it indicated that it is rated at 4.4 amps, open circuit 21.7 V rated at 17.0 V  From what I have learned in the forum this should be a 12 volt panel. (?)

Yes, that’s a “12 V” module. There may some slight performance degradation after eight years of service, but it should otherwise be fine.

I went to Northern Arizona Wind and Solar … and drooled over the Morningstar ProStar 30M, this looks like the ideal choice, thanks for the suggestion. It looks like I will need a shunt too. (?) I'm not sure what a shunt actually does?

The PS-30M is a very good 4-stage controller. I used one on my RV for several years. You can study the controller’s specs and operation by downloading the owner’s manual from Morningstar’s website (www.morningstarcorp.com). You may wish to consider the optional remote battery temperature sensor for this controller.

A shunt is a calibrated resistor used for measuring current flow and direction. There’s no need for one in your system unless you plan to add a battery monitor such as a Trimetric or a Xantrex Link-10

I will be under 300 watts with anything I use that is 120 volt.  I looked at the Samlex 300 watt 12 volt sine wave inverter, its more affordable and appears to be what I need.  Is this a good choice?

Inverters typically operate most efficiently at ~1/3 to ~1/2 of their rated power. Accordingly, you may wish to consider a 600 W sine wave inverter for your 300 W load.  I don’t know about the Samlex line. I’ve had very good luck with my Exeltech 600.

… I was thinking not only about the cost of gas to run the generator but also the cost of the gas in a full size Bronco just to go get it.

Another option to consider in a pinch would be to connect the Bronco’s alternator directly to the battery bank (via the trailer connector?) and just run the engine for a while. It’s not very efficient, but it might be less inefficient…

I'll be throwing 36 amps into the battery bank when charging them with the generators.

Don’t count on it. An automotive type charger may be rated at 12 A under ideal conditions, but output current typically drops off as the battery voltage increases, and the charging voltage using isn’t high enough to fully charge the batteries (~14.4 V required at 77 degrees F). These chargers will help with initial recharge, but a quality deep-cycle battery charger is what will fully and correctly recharge your batteries.

Something I'm pretty confused on:  I have three 12 amp battery chargers that I intended to plug into the generator and just clip the leads on to the batteries for that once a week or so charging in the winter and then take the clips off until the next time.

Can I run the charging wires directly to the controller and and mix them in with the charging wires from the solar panel?  This seems like a much better way to use the 12 amp chargers and would guarantee that I would not overcharge the batteries.  Plus no sparks.

NO! The charge controller regulates charging current in Absorb, Float and EQ modes by rapidly switching the energy source on and off. The chargers probably won’t react well to that. Also, their charging voltage probably isn’t high enough to fully charge the batteries. You can avoid sparks at the battery terminals by connecting the auto battery chargers through a marine battery switch.

http://store.solar-electric.com/basw1300amp.html

As suggested, I checked with the dealer that sold me the batteries and with these specific four batteries in a bank with the 36 amps from the 12 volt chargers plus the charge from the solar panels at the same time I will still be below the maximum acceptable charge so that I do not throw too much into the batteries at once.

The max charging current for your 480 Ah flooded-cell battery bank is in the 48 A to 62 A range (10% to 13% of capacity, per Trojan recommendation).

Where does the electricity go when the controller decides that the batteries are charged?

In general, the controller passes full available power from the PV array to the batteries when operating in the BULK mode. Once the battery voltage reaches the ABSORB set point, the controller enters a current limiting mode to hold the ABSORB voltage steady. The controller does this using PWM technology to rapidly turn the PV array on and off. The PWM “ON” duty cycle, along with PV array size and battery capacity, establishes the charge current for the ABSORB voltage. The controller works similarly for the FLOAT and EQ voltage set points.

When the controller’s PWM operation in “OFF”, the connection between the PV array and the controller input is opened. The panel briefly operates at its open-circuit voltage, but no current flows, so no power is produced.  The controller typically operates in the ABSORB and FLOAT modes in the afternoon after the BULK cycle is complete, so this is a good time to power small loads that can make use of the unused energy but without affecting the ABSORB mode.

You’re also going to need to learn about maintaining your deep-cycle battery bank. Trojan Battery’s on-line guide may be helpful.

http://www.trojanbattery.com/Tech-Support/BatteryMaintenance.aspx

Finally, your four 12 V batteries should be connected in parallel, and the cables between the bank and the controller should be connected at opposite ends of the bank. This diagram may be helpful (see diagram on the left of three 12 V batteries wired in parallel as an example).

http://www.solarseller.com/battery_bank_wiring_diagram.htm#12_volt

HTH,
Jim / crewzer

niel

Re: Small system need advice

arch,
i'm going to elaborate a bit on the max charge for batteries and before i do i'll let you read over a previous link.
http://www.wind-sun.com/smf/index.php?topic=1513.0
now it stated that other batteries can take 25% charge rates and yet a better than average battery manufacturer(trojan) states to 13% and i said 10%. we all do agree nearly every battery can do 13%, but in those previous discussions i also stated that there will be a higher maintenance on the battery due to increased boiling of the electrolyte. common sense. now in the case of generic or general batteries (you didn't specify a manufacturer) there's another consideration and that is the general construction of the cells and the housing. do i dare say to you that a generic battery that isn't made as well as the trojan should be run to their same max charge point? more electrolyte boiling means more heat is being produced and can warp the plates and cause sagging in poorly designed batteries and housings. this may take time to do as you probably won't see this happen like an immediate melt down so i'm saying the cheapo batteries could have their life expectancies reduced in addition to the increased maintenance. high discharges can have a similar effect. there really aren't any specific set boundaries that one could say for sure as i'm quite sure even trojan wouldn't care if you charged at 13.1%, but for their warranty you better be at 13% or lower as that technicallity could stop the replacement of a battery that is faulty.
your best bet is to contact your battery manufacturer and get their lowdown on your battery. for general/generic battery types i think i'll continue to say about 10% with up to 13% with caution for the maximum, but there isn't any specific point that makes it all fall straight to hades. see if in your case they get 55amps(11.46%) i wouldn't care and neither should you as long as you are aware in general of what this means. even if you give a battery bank 13.1% for it's charge and feel uneasy about it, just put a constant load on it of that .1% or more to just error on the side of safety.(using that term loosely) that .1% is nitpicking and doesn't make a big difference overall in comparrison to going farther out on the limb. now i do believe if you picked a 7% rate of charge that this would be better for the battery lifespan than that of nearly doubling it by going with 13%. that does not mean that any of you should be designing your system with 5 and 6 or even 7% charge rates for extra battery life as the time needed to get the charge back into the battery becomes a factor and long times of not being fully charged will also take away battery lifespan. a 5% rate of charge is a 20+ hour rate and everybody knows the sun doesn't shine 20+ hours of the day excepting some in the arctic circle areas. we have previously gone back and forth on the subject quite a bit, but now nobody does argue the range of 5-10% for charging any battery. do be aware that this is actual amperage charging the batteries as loads can be on during the charging time that change the actual rate. in other words you're not giving a battery bank 55amps if you have a 10amp load on at the same time giving a net 45amps for charging.
i know i editorialized this a bit, but it's just food for thought on the subject. you now have a general feel of the subject matter and a better understanding.

mike95490

Re: Small system need advice

Arch wrote:

I will be able to boost the amount of amp hours in my battery bank when I run the generator
for the washer/dryer, power tools, etc. but do not want to run them much just for re-charging the batteries. How will this affect the batteries if I don't completely re-charge them or just throw partial charges into them when running the generator for short periods of time?
I have three 12 amp battery chargers that I plan on plugging into the generator and clipping to the batteries while the generator is running. Is this wise?
Is it OK to charge them with the generator at the same time the solar is charging them?

If it were my money, and batteries, I'd skip the 3, 12A chargers, and look into one of the Vector chargers, yes it's an automotive type, but it's an advanced type, and has a 3 stage charge, not sensative to AC voltage sag either. and you can drag it around for other useses. Look at the 40A model - VEC1093A. Northern Tool has good prices on them.

Gasoline - if you are storing for several months - don't forget to get a stabilizer additive - least you gum up the works.

If your PV is going up on a water tank, any way to mount a wind generator up there - or any wind in your location to catch in the winter ?

Have you considered LED lighting? Way less power than CF - and no ballasts to fry.

Shunt - as in measuring Amps?? or shunt, as a dummy load when the summer sun has charged the batteries, and they are starting to boil?? Some charge controllers need one, some don't.

Good luck. Mike my PV page: http://members.dslextreme.com/users/mike90045/mikessolarinstall.html

niel

Re: Small system need advice

mike,
i agree with all you have said as a dedicated 3 stage charger will far outperform those other open ended chargers. the iota is like this. this does good for the battery by giving a proper charge to it and helps in preserving the life of any battery.
it gets to be a pain with the preserving of gasoline. i suggest cycling it monthly if you have a car.(assumed) dump it in the tank after a month and go get more gas for your gas cans. it might be easier to syphon it from the car's tank and fill them with it. you may need a few extra cans to work it out, but you get the idea anyhow.
cfs and leds are both good, but it depends on the application. leds for their light output do not outperform cfs. leds have very long life, but also tend to be narrower in spectral output meaning you have more light towards the blue section of the spectrum. they also aren't as exacting in that spectral output even among identical leds. leds do work in the cold and damp areas better than cfs.

System2

Re: Small system need advice

Thanks again for all of the input.

The distance between wondering why and knowing why is a pretty large gap, as the picture clears I find that figuring out and putting this solar system together correctly is going from tedious to fun.

Conclusions based on the forum's advice and experience:

The three automotive battery chargers that I had intended to use once a week to top the batteries off in the winter is the slipshod way to do it. I need to bite the bullet and do it right. This is not an option, my property is extremely remote and subject to being wintered in from time to time in the winter.

The Xantrex TC-40 hard wired into my battery bank will charge the batteries the way they like to be charged plus provide temperature compensation and battery equalization, this charger looks like the perfect solution. With no cycling under 50% and no overcharging they'll last me a long time.

The 800 watt modified sine wave inverter just won't work. A pure sine wave inverter is mandatory for the few AC items I need it for. (Electronics, etc.)

Is the electricity I will be putting out directly from the generators a modified sine wave?

Since I will only use the inverter occasionally and will not reach a demand of 300 watts at any given time I will get a 600 watt pure sine wave inverter and it will not reach 1/2 of its rated power for more efficiency. I hope the Samlex 600 will hold up for occasional use?, it's within my budget.

My small generator is a Honda EM2200 that I purchased new at least 15 years ago for remote camping. Bill's example of gas consumption vs. amp hours generated was for the EU2000i and compared to my generator this should put me in the ball park. I also have a new 4500 watt generator (clothes dryer, air compressor, backup, etc.) that I can charge the batteries with if all else fails.

The water tower will support two 250 gallon stainless steel water tanks which will put the bottom of the tanks 12' high. The only water source is an ancient, shallow hand dug well (water tested good) that will have a small 120 volt AC submersible pump to fill the tanks which will gravity flow the water back to the cabin and when necessary be boosted by my 12 volt pump. I will have to use the generator to fill the tanks occasionally but the tradeoff will be less use of the 12 volt pump (gravity pressure) and a saving of amp hour draw from my batteries. I can also charge the batteries if needed while I fill the tanks.

There will be a solar thermal collector for hot water on the tower which will drastically reduce the use of the propane hot water heater.

I plan to build a deck on the south side of the water tower to hold the panels with a way to compensate for the vertical tilt (58 degrees + or - in the winter) but nothing as elaborate as a tracking system? Tracking is not practical where I will be, I would rather add another solar panel.

I considered wind as Mike suggested but the wind is "light and variable" for too many days and nights so sun is by far the most reliable source.

Thanks for the heads up on gas storage for the generators, I have a little Honda 125 dirt /street bike ( Now that's something that will be getting a lot of use!!!) so I factored in a large enough storage tank for both and will keep it topped of by bringing gas back as I go out once a month or so in the Bronco. By continually replenishing with new gas this should mix with the existing gas in the tank and keep it fresh?

I've come a long way since I found the forum and at 63 I have lots of time to have fun but not enough time to do the solar system over again the right way. It's going to be a sweet little system.

Thanks,

Arch

BB.

Re: Small system need advice

The modified sine wave inverter could work OK... Really depends on the load and the quality of the inverter--something that we cannot tell from here. Long term, you will want the sinewave inverter. Short term, it is a toss of the dice.

Regarding the generator... I am looking for specs. on the EM2200--All I have found so far is that it will run for 9.4 hours (2.9 gallon fuel tank) at full load (2,000 watts?) or:

kWhr/Gal=2 kWhrs * 9.4 hours/2.9 gallons = 6.5 kWhrs/Gallon

Better than the fuel consumption against the eux000i family (at least at full load).

A standard generator will give you a pretty good sinewave--but it will very in frequency quite a bit--usually not a big problem unless you have something very frequency dependent. The Honda (and others) "i" family is for inverter--frequency and voltage will be quite stable (except for issues of heavy starting loads) and, from what I have read, a reasonable sinewave.

Unless you are using a drier with electric heat (which I would recommend that you not do if possible), you should not need the 4.5 kW generator to run the washer and drier--but use the smallest generator possible (use a Kill-A-Watt meter or equivalent to measure load). Typically, large gensets running at "light" loads will burn fuel pretty inefficiently.

-Bill

mike95490

Re: Small system need advice

Arch wrote:

Thanks for the heads up on gas storage for the generators, I have a little Honda 125 dirt /street bike ( Now that's something that will be getting a lot of use!!!) so I factored in a large enough storage tank for both and will keep it topped of by bringing gas back as I go out once a month or so in the Bronco. By continually replenishing with new gas this should mix with the existing gas in the tank and keep it fresh?

Don't mix, drain one tank, and start another. You want several small tanks, with small airspace in them. Airspace = condensation = water in your gas, which is different from it going stale and sludgeing.
Will your water storage freeze up in winter? The well/spring ?
At least once a week, or whenever the generator is fired up, use the big charger, and bulk up the batteries. let the solar supply the finish charge, unless they are staying too low.