Hi, I’m planning on replacing my battery bank soon. At night we use about 3kw every hour, sometimes a bit more. I have a 10kw inverter with 12960 watts of panels total on this system charging at 48 volts through 4 charge controllers, although we only use about 7500 at peak during the day, the rest clips, but we get full usable power from about 7 AM till 4 PM. I was wondering which would be better, 24, 2v 2000 ah batteries or 36, 12 volt 200 ah batteries. I want to power it most of the night from the batteries. Also are the 2v batteries better, they are rated to last 20 years?
thanks, the dog
Yes, i would definitely go with the 2000Ah 2V batteries (as long as they are from a reputable manufacturer). Using the single cell (2V) batteries means you will only have 1 string of batteries.
When using 12V batteries you can have lots of issues with battery balancing in multiple strings.
The 24 x 2v, 2000Ah batteries will create a 48kWh battery bank. However you should only discharge 30% on a daily cycle so 16kWh usable capacity. With the conversion and inverter losses this will be approximately 14kWh.
Wondering how do you use 3kW per hour over night? That is a lot of power! Over night that will add up to 30kWh?
Yes! We use lots of power. Here we don’t use central a/c, it’s all mini splits or wall units. At night we are using 2, 1hp inverter type wall units and 2, 1 1/2 hp inverter split types for the bedrooms. Also there are 2 full size refrigerators and 2 compact refrigerators plus about 70 watts of indoor lighting and 200 watts of outdoor security lighting. During the day there’s some TVs and microwaves in use plus the heat outside causes the a/c units to work harder so we use a lot more power. Those are on our main system with the battery bank, that’s also backed up by a generator. The a/c units for the living areas, the irrigation pumps and the pool pump are set on water heater timers so they only are on during daytime when we have solar power and are powered by other inverters. During normal weather periods the usage is a bit below the 3kw, but in hot season it can hit 3.8-4kw per hour at night.
Would you have any suggestions on batteries which might be less costly that would power the house most of the night? I appreciate your help. the dog
dog,
i don’t have notting to say about the batteries but…i think you have a powerful system after the first problems solved and the investments that you did
but,that’s my opinion,was it not better to start with a good isolation from the house so that it keep cooler inside the house(i think 10 to 15 cm EPS for walls and roof)
then you need less electricity,solar panels,inverter batteries and so on…
this is advice to anyone who want to save…
Ugly Dog, …Can’t be a Blue or Red Healer 
BTW: Hosing-Out the Outside Air-con Radiators, should/will make dirty ones more efficient, a bit like cleaning solar Panels.
If only all forum posts could be so informative. 
In reality, I believe the Energy Storage Leader in 2020 has become Super Capacitors (SC), there are several material, chemical combinations used by several manufacturers.
However Graphite & Graphene SC are the best when comparing DOD & Charge rate.
Unfortunately the Cost of SC Technology comes in from approx $1’000kWh.
We hear all the Arguments saying “Batteries take to long to Recover the Cost”, that is what I call misguided statement, as it should be about becoming Energy Independent, as that is what the correctly sized Energy Storage Provides.
The house is fairly well insulated, the walls are 1ft thick solid concrete, the roof is insulated with a foam sheet attached to the roof panels, even on a hot day you can go into the attic, and the new part of the house has flat concrete roofs about 6 inches thick, in that part the ceiling feels cool even on the hottest days. The windows are terrible, I’m in the process of weatherstripping the outside security windows and we installed new windows on the inside, rather like the old fashioned storm windows people used to use in cold climates, just in reverse, instead of keeping the cold out, we keep it in, plus heavy curtains on most of the windows and glass doors.
Also, yes I clean our aircons about once a month, both the evaporators and condensers and I clean the filters weekly. I use a mixture of dish soap, vinegar and water, then rinse them, it works pretty good. I know most places the payback is rather slow, but here in The Philippines the electricity is so expensive that, based on the savings we already have, we expect the payback for the panels, inverters, the structure we built and the labor will be about 5 years and if we add a battery bank that costs about $15000 US we will pay that back in about 5 years as well.
I’ll check out the super capacitors, thanks for the input. the dog
Hi, I have another question. It gets really hot here in the late spring early summer, 37-45*C the batteries get hot as well averaging about the same temperature. I was thinking of building a stand with the bottom and sides made of hardee board insulated with foam and the bottom and back covered with pipes coming from the well leading to the house water system to help keep them cool. It wouldn’t use any extra electricity since the water would be pumped by the well when it comes on to supply water to the house.
Any thoughts on that? Or am i nuts? the dog
Hi dog,
You gone need a lot of pipes and continues water trough it,but i am almost sure that it’s never gone be enough to let your temp.go down
I think its more helpfull to make that room,you need space for this set batteries,complete tight isolated with the needed holes for ventilation on top and from somewhere a pipe, from inside the house,with a fan pushed chilled air under the batteries
And concrete accumulate the heat it’s not a isolator,it’s help to make yr walls and roof stronger but isolation make a lot more sense
Good idea. Maybe I would be better off if I leave a bit of space between the batteries and put a small evaporative a/c unit in the wall to blow cooled air over them. I am putting a new roof on the power room and I plan to fully insulate that and add hardiboard for ceilings to keep heat transfer down as much as possible since the temperature on it gets up over 50* on a sunny day.