Size Batteries to Array or Array to Batteries

[swamp]

It's been a while since I've been here and need some good advice. I have an off grid cabin in the mid-central UP of Michigan. We use very little power, but do have several 10W 12v LED lights that we use during the hot summer months instead the heat generating gas lights. At night we run a 110v small table top fan. We have a 110V cell signal booster that we use a few minutes each day and that's about it. My current set up is 4 Renogy 100w panels with a commander 30A MPPT controller and two North Star 200aH batteries. The 12v LEDs are run off the load side of the controller and the 110v stuff is powered by a 3000W sine wave inverter rated for 30A. Mostly we are there from Friday evening to Sunday evening, but twice a year we spend about 10 consecutive days there. The system works well for me, but I came across a deal that was too good to pass up.
I was able to purchase 36 sealed AGM 83aH batteries that were in a UPS system that I take care of. I know for a fact that the system has been maintained and that these batteries have only been discharged once in the 5 years since they were installed. Manufacturer says they are rated for up to 300 complete discharge cycles. All voltages and resistance readings were perfect so for $200 I couldn't resist. Now that you know about my screamin' deal I'd like to upgrade my whole system to allow me to convert to a 110V well pump. The current pump is a 1/2hp 240V pump that requires me to run the generator meaning I have to go out to the well shed and manually start the genny. Not horrible, but it can be a pain especially when it's raining. I would like to replace the pump with a 110v 3/4 hp with a 120' of lift and run it off of my solar array.
My question is, should I use all 36 batteries? Since my power usage is very limited even with the well pump, which even with showering only runs 4-5 times in a 24 hour period: is 36 overkill? If not, do I need a monster solar array or can I get away with say 1200-1500W array? Winter visits are far and few between so the 2-3 hours average daylight shouldn't be a factor since the visits during winter could be 3-4 weeks between. Summer is closer to 4-5 hours of sun/day and about 5 days between stays. Should I go 24V or 48V? I'm leaning towards 24V. What inverter and controller would you recommend? What do you experts think?

[bcroe]

My thought would be stick with the generator, perhaps work up a better remote start/stop. Next best would
be a DC well pump, possibly at higher voltage. The batteries will easily handle starting surges, the panels
would probably need expansion for the limited usage. If you go for an inverter setup large enough to start
your AC pump, it will involve a complete, much larger system that will mostly be unused. good luck, Bruce Roe

[Sunking]

You have some issues. First last thing you DO NOT want to have parallel batteries. Second those batteries are not made to be cycled. They are telecom batteries made to be used in a UPS and be discharged in 15 minute to 1 hour. Telecom Emergency Standby Battery Systems can use parallel batteries because they are in FLOAT SERVICE there whole life and rarely if ever discharged. You got them so cheap because your company turned a liability into an asset. It would have cost them significant cash to have them removed and disposed of properly which is now your problem to deal with. As you noted the manufacture only claims 300 cycles, which is about 1 year in cycle service. With multiple parallel strings far less cycles, maybe 6 months. Telecom batteries since they are not cycled battery life becomes Calendar Life and sealed batteries calendar life is 5 to 7 years for most up to 10 years with a high end C&D, and Enersys.

Now to your questions. If given the choice the higher the voltage the better as to minimize parallel strings. You did not mention what voltage the batteries are, but only use the number required to make two parallel strings which you will end up with 48 volts @ 166 AH. Sell the rest as boat anchors or to other newbies who do not know what the batteries are made for. Recover as much money as you can so you can buy all new batteries when the ones you have die within a year or so.

Sealed AGM batteries like those you have really do not have minimum and maximum charge rates like FLA or Gel Pb batteries. So it really comes down to determine how many watt hours you use and worse case which sounds like you 10 day run. At 166 AH you can go as low as 10 amps @ 48 volts = 500 watts or as high as 100 amps @ 48 volts = 5000 watts. If the panels and controller you have now work, use them as there is really no lower limit on AGM batteries like there is with FLA. It just becomes a question if 400 watts of panels can generate and replace what you use in a day. In winter in UP, essentially you have no useful sun hours in winter. 1 Sun hour would be a good day. Summer about 6 Sun Hours. With a 400 watt panel in UP is good for about 300 watt hours per day in winter. With a FLA battery only requires 12 volts @ 125 AH, 24 volts @ 65 AH, and 24 volts @ 35 AH. So based on that with the batteries you have 24 volts @ 83 AH is over kill with a single string. Get rid of the rest.

[Andy Muzik]

Swamp, I have a remote cabin in UP also. No power within 5 miles. I have been considering solar for a few years, but a propane genny is still the most reliable and least costly solution for us. We run a Honda 2000i for all of our loads and a 5 kw split phase for well pump. We are able to have all the comforts of home and not have to worry about the sun, batteries and all that goes with that. We will have some form of inverter, batteries, and panels one day just to have some quite time at night, the generator noise drives me nuts at nite while all the younger ones are up late playing cards with tv on.

[swamp]

Sunking and bcroe you guys are why I'm here. I need honest educated opinions. That said I am not sure I understand everything that was stated. The batteries I just bought are 12V and with the little education I was intending to run two parallel strings of 12V to get 24V. The company I work for had paid to have the old batteries removed and new ones installed. I actually purchased them from the service company which was the only legal way I could do it. The two metal recycling companies a couple of miles down the road offered me 21.5 cents per pound so that's about $420 in scrap price and I double my money if I just scrap them. I figured in the least that loading them on my truck and driving a couple of miles and making $220 for an hour of my trouble was pretty good. That's more than I take home after two full days of work for about an hour of work. Anyway, I can scrap them out if you guys say they aren't worth messing with.
I figure that we use the cabin about 120 or so days a year so at 300 cycles that should give me about three years of use. For $200 I thought that was reasonable. I wasn't expecting for them to last much more than that. Our company will be replacing that UPS system in 2-3 years with a modular one so I will have another supply of batteries when that happens. I figured that in about 6 years or so I will have saved up enough to buy the right batteries. Since I really don't know this stuff I need to ask why running two parallel 12V to get 24V or two parallel24V to get 48V is bad. Honestly, I'm not trying to argue and I believe you I am just wanting to learn why.
This is absolutely why I'm asking. Eventually I want to have a good system that will sustain the energy requirements when we spend longer periods of time at the cabin. From what I see of the 110V well pump the amp draw after initial surge is minimal. I still need to find the surge amps at start depending on which pump I choose. The 240V one I have now runs on a 15A breaker and the preliminary checking I did showed the 110V pumps with 3.2A draw and using the 10x formula that's only 32A at start.
All this said can you guys clarify for me. Should I just scrap these or is it reasonable to expect a couple of years out of them. Can you please explain how to hook up the batteries to be the most efficient for what they are and get as many cycles out them as possible? It seems like Sunking is saying that I should use only 4 batteries since these are 12V to get one string of 48V. I was hoping that this could be a step in upgrading the solar panels, controller and inverter so that down the road I would only need to buy better batteries.
One final thought about the generator. It is a 4400 watt and a very basic propane one that runs off my 1000-gal pig. It has electric start, but due to a purge that is required at each start it would take a some engineering to get remote start to work. It can be done with a small 12V actuator that can be manually switch operated to perform the purge and then run the ignition and purge wires into the cabin.
Maybe I just scrap these, double my money and buy another 12V battery for my current set up. What do you guys say?
Swamp

[Mike90250]

I 'd concur with Sunking - hold back 9 batteries (1 as a spare) and sell the rest (use a volt meter and keep the 9 highest voltage ones)

If you have plans to move to the site full time, you will eventually want a 48V system, so may as well start it now with 2 strings of 4 batteries [ 4s2p ] for 48V

When temcom cells are rotated out, it's because they are beginning to reach the end of their useful service life, so you might get a year of weekends out of them.

[swamp]

Andy, good to hear from a fellow camp owner. We're North of Crystal Falls closer to Covington how about you? I hate having to go out and start the genny and I hate listening to it run even though it's for short periods. I have a second smaller 3400watt propane genny that is quieter and I use that to charge batteries if we have several cloudy consecutive days and other various sporadic uses. That one doesn't have 240V capability so I can't use it for the well pump. That is another reason I want to switch to a 110V well pump. If my larger genny ever takes a dump I don't have back up 240v power. That wouldn't be the case if I had a 110V pump. During the winter we use almost no power with all of the gas lights, fridge and heat so the lack of useful sun isn't a big deal. So do you think If I were to keep a second batch of batteries here at home on a tender would they stay good for a year and then I could get two years between the two batches? Maybe I would be further off to just add another battery to my current unit and upgrade my panels. The thing is if I could have made a better battery bank out of these I could have sold my current set up to some friends who are just getting started in solar power for their off grid camp. I was going to use that money to help buy 4 320 watt panels and a larger controller. My current controller will handle more panels at 24V, but my inverter is a 12V unit.
Swamp