# trying to cycle my batteries

Solar Expert Posts: 54
so i have a 12 volt system
with 4 rolls surritte 6 volts in a series parallel

these rate at 350ah at 20 hrs so in theory i have 1400 ah in total and running it down to 50%dod i should have about 700 ah available(correct me if wrong)
i currently use less than 10% of this and am worried about the effect this may have on the batteries

im interested in setting up a water pump to help me cycle my batteries more while figureing out how many panels i need to compensate the loss

i currently am using 9 sp75 75watt panels ,two 48watt panels , 2 70 watt panels all connected parallel strait to a combiner through a breaker into a c60

I have 8 more sp75 panels that I could use

these panels say 4.5 amps at 75 watts but are a little old
when i touch the volt meter to the combiner it says just under 20 volts with the current array

if i max out the controller at 60 amps how long would it take to recharge 700 amp hr does this mean I'm putting 60 amps from the panels to the batteries per hour??? not quite sure how to do the math on that one
when I run the generator it says im putting in 22amps does that mean per hour??

the 1 hp pump i was planning to use says 770 watts at 8 amps 120v does this mean I'm pulling 8 amps an hour to use???

sorry if these questions are redundant
thanks for any input

• Solar Expert Posts: 235 ✭✭
Re: trying to cycle my batteries

I think you misunderstood that other thread. Generally you should not cycle your batteries for the sake of cycling, it will just wear them out. There is an exception for continued very shallow cycling, not sure if that applies to you or not. Even if it does, note you would only want "a little" more not say 50% DOD. This is from the battery FAQ from our host here:
Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film.
• Solar Expert Posts: 54
Re: trying to cycle my batteries

thanks i understood that im just trying to figure out how much power i can pull out of these batteries

i need to pump the water somehow

i just want to know how many hours i can run my pump while being able to replace it later with my panels

i just feel since im reaching float while hours of sun go by i could be useing that power to pump water while cycling my batteriess hopefully in the 20-40 % range
i would go with direct current but the wire run is 150 feet and with a 12 volt system id be into some large wire
maybe my 1hp submersible well pump in a cistern would use less power and being ac current id get away with smaller wire

what do you think?
• Solar Expert Posts: 235 ✭✭
Re: trying to cycle my batteries

if i max out the controller at 60 amps how long would it take to recharge 700 amp hr does this mean I'm putting 60 amps from the panels to the batteries per hour??? not quite sure how to do the math on that one

Is basically the same as power vs energy - watts vs watt hours. Think of "amps" as current flow at a given moment in time - that is power and says nothing about how long you will be doing it for. When we talk about current over some length of time, now we are talking about energy. An amp hour is an amp for an hour, .5 amp for 2 hours, a millionth of an amp for a million hours, etc. So if you have a 60 amp supply and you want to put 700 amp hrs into a battery, it will take 11.66 hours. But that is assuming a perfectly efficient battery, so figure for every amp hour you take out, you will need to put 1.25 back in.
when I run the generator it says im putting in 22amps does that mean per hour??

if it was connected for an hour yes you would be putting in 22 amp hours. 6 minutes would be 2.2 amp hours
i just want to know how many hours i can run my pump while being able to replace it later with my panels

You will need to know what the pump draws, or in the case of a 120v pump run off an inverter, what the inverter draws. Its not so simple and best to get it right form the horses mouth and measure it directly. Depending on the pump, the nameplate current may not be very accurate, it may vary quite a bit with load/head/pressure, and you have to figure inverter losses. What will you be doing with all this water?

I hear you about wanting to utilize all the energy coming from your sources.
i do all my charge control with diversion so I can heat water. I hate seeing those electrons just sitting there......
• Solar Expert Posts: 106 ✭✭
Re: trying to cycle my batteries

First things first: your battery bank is not 1400Ah. Batteries in series, voltage adds up and Amps stay the same. Batteries in parrallel, voltage stay the same and Amps add up.

So, to make a 12V battery bank out of 4 x 6V @ 350Ah, you connect 2 batteries in series which ends up being 12V @ 350Ah. Then you take 2 such strings and connect them in parrallel and you end up with a bank that is 12V @ 700Ah.

You should reassess your situation on those terms. Good luck!
Off-grid cabin in northern Quebec: 6 x 250 W Conergy panels, FM80, 4 x 6V CR430 in series (24V nominal), Magnum MS4024-PAE
• Solar Expert Posts: 54
Re: trying to cycle my batteries

thanks for the update
so now understanding i have 700ah battery bank that would give me 200 amp hours at a conservative 40% discarge

to replace that with my panels putting in a conservative lets say 50amp instead of 60 due to losses im i right to assume that i could replace the loss with 4 hours of sun on the panels

my pump says 8 amps but even at 15 amp would i be able to run this pump for 6 hours and still have extra for house stuff assuming im pulling 90 amps with the pump
im planning on running the pump to its maximum head 207 feet the flow at that head is a low flow of 1 gal per min giving me 360 gallons a day hopefully

i could hook this pump to a plug and run it through a kill a watt meter while on the genny to get an idea of the power draw

thanks for all the help
• Solar Expert Posts: 140 ✭✭
Re: trying to cycle my batteries
the 1 hp pump i was planning to use says 770 watts at 8 amps 120v does this mean I'm pulling 8 amps an hour to use???

Keep in mind that 8 Amps @ 120V = 80 Amps @ 12V.

To run this pump for one hour would use 80 Amp-hours from your 12V battery bank (not including losses from system inefficiencies).
• Solar Expert Posts: 3,123 ✭✭✭✭
Re: trying to cycle my batteries
when I run the generator it says im putting in 22amps does that mean per hour??

the 1 hp pump i was planning to use says 770 watts at 8 amps 120v does this mean I'm pulling 8 amps an hour to use???

sorry if these questions are redundant
thanks for any input
I think that a large part of your confusion is your mixup regarding units of measurement.
Amps tell you how much current if flowing, right now. If you multiply amps times volts you get watts, which tell you how much energy you are using per second, right now.

If you use energy at the rate of 50 watts for two hours, you have used 100 watt-hours of energy. Note that this is watt-hours, not watts per hour.

Think of it like using gas at the rate of 1 gallon per 30 miles and you multiply by the number of miles to get the number of gallons. Or in a plane using fuel at 100 gallons per hour and flying two hours uses 200 gallons.

Just as with watts and watt-hours, you have amps and amp-hours.
Your battery capacity is measured in amp-hours.

A pump that uses 8A at 120V will use 80A at 12V. And 80A for two hours means that you are draining the battery 160 amp-hours (AH) over the course of two hours.
Note also, just for grins, that 1 amp is equal to one amp-hour per hour.
SMA SB 3000, old BP panels.
• Super Moderators, Administrators Posts: 32,641 admin
Re: trying to cycle my batteries

I like to use the multiply symbol between the units--Makes more sense to me:

Amp*Hour
Watt*Hour

Or just AH and WH (multiplications assumed--just like Algebra).

You will sometimes see Amp-Hours or even Amp/Hours too... But they really mean AH or A*H.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 54
Re: trying to cycle my batteries

do you mean if i invert 8A at 120v from my 12 volt bank then i lose 80A
• Super Moderators, Administrators Posts: 32,641 admin
Re: trying to cycle my batteries

Basically, the answer is yes:

Power = V * I = 120 Volts * 8 amp AC = 960 Watts out from the inverter
Power / V = I = 960 Watts / 12 volt battery bus = 80 Amps DC (at 12 volts)

No free lunch, reduce voltage to 1/10th, then current has to increase 10x (120 VAC vs 12 VDC).

The AC vs DC does not matter in the basic equation.

Of course, there are more details--When you are ready.

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