# I'm ask this question

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Solar Expert Posts: 51 ✭✭✭✭
If 13 watts equal 1-amp hour out of the battery unit so how many watts per hour is my draw out of my system x-10 battery string system .-x-255 amp hours per battier-x-10 battery string for total -x-2550 amps total for the string of 10 batties ..

So how many watts total for the whole single bank

• Super Moderators, Administrators Posts: 33,479 admin
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Re: I'm ask this question

If the batteries are connected in parallel, then the amp hours add.
In
Note, for longer battery life, try to not discharge more than 50% of capacity.

Also, having a lot of batteries in parallel makes it difficult to balance current equally through all batteries equally.

Charging watts: 2,550 ah x 14.5 volts = 36,975. WattHours in
Discharging watts: 2,550 ah x 12.0 volts = 30,600. WattHours out

The above numbers are approximate.

There are lots of issues with lots of batteries in parallel. Is there some reason you need this setup?

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 10,300 ✭✭✭✭
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Re: I'm ask this question

welcome henry,
1st of all 13w will not be 1a for a battery. the nominal voltage for a battery is 12v and watts/volts=current. 13w/12v=1.0833a.

also with concerns for why this large of a 12v battery bank aside, the wh is as bb states 12v x 2550ah = 30,600wh (30.6kwh) of which up to 15,300wh can be considered usable.
• Solar Expert Posts: 226 ✭✭✭
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Re: I'm ask this question
henry1 wrote: »
If 13 watts equal 1-amp hour out of the battery unit so how many watts per hour is my draw out of my system x-10 battery string system .-x-255 amp hours per battier-x-10 battery string for total -x-2550 amps total for the string of 10 batties ..

So how many watts total for the whole single bank

What kind of batteries? 225 ah sounds like you're talking about 6V golf cart batteries.

If that's the case a single 225 ah golf cart battery is good for about 675 watt hours assuming you only drain it about 50% (deeper discharges will quickly wear out the battery)
So 10 batteries are good for about 6,750 wh.

If you are talking about huge 12V 225ah batteries (weighs about 150 lbs each?) then double than number: 13,500 whs

P.s. please don't put '-x-' in you posts, it makes it hard to read
• Solar Expert Posts: 51 ✭✭✭✭
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Re: I'm ask this question
Peter_V wrote: »
What kind of batteries? 225 ah sounds like you're talking about 6V golf cart batteries.

If that's the case a single 225 ah golf cart battery is good for about 675 watt hours assuming you only drain it about 50% (deeper discharges will quickly wear out the battery)
So 10 batteries are good for about 6,750 wh.

If you are talking about huge 12V 225ah batteries (weighs about 150 lbs each?) then double than number: 13,500 whs

P.s. please don't put '-x-' in you posts, it makes it hard to read

First off Sorry about that ..I was trying to times the batties by the number of ten to make a total single string of ten batterys in the string and yes that one the huge 12V 225ah batties that way 150.pds each .

I would like 10 each of those batties in each of the battie strings for use on the cabin design ..
• Solar Expert Posts: 5,183 ✭✭✭✭
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Re: I'm ask this question

Hi Henry,

to be clear : Are your 10 - 12 v batteries in series or parallel?

If the batteries are in series you have a 120volts and 225 amps

If the batteries are in parallel you have 12 volts and 2250 amps.

This is a very important issue. Which do you have?

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• Solar Expert Posts: 51 ✭✭✭✭
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Re: I'm ask this question
westbranch wrote: »
Hi Henry,

to be clear : Are your 10 - 12 v batteries in series or parallel
If the batteries are in series you have a 120volts and 225 amps

If the batteries are in parallel you have 12 volts and 2250 amps.
That's what I'm trying to do.
• Solar Expert Posts: 292 ✭✭
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Re: I'm ask this question

Going with the 10% rule, you will need at least a 225a charger to keep that kind of battery bank happy.
• Solar Expert Posts: 9,583 ✭✭✭✭✭
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Re: I'm ask this question

It's very difficult to get 10 batteries to charge well in parallel, without 1 hogging all the work
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

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• Banned Posts: 17,615 ✭✭✭
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Re: I'm ask this question

Mike's got it.
Trying to build a 27 kW hour battery bank (2250 Amp hours * 12 Volts) on a 12 Volt system is nearly impossible.
On a 48 Volt system you would have only need 3 parallel banks to get 32.4 kW hours. Far fewer problems with current sharing, high Amperage, et cetera. If you need this kind of power you really should up the system Voltage.
• Super Moderators, Administrators Posts: 33,479 admin
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Re: I'm ask this question

Here is a quick explanation of how to connect multiple parallel batteries properly:

SmartGauge Electronics - Interconnecting multiple batteries

Note, you should have fuses with each battery (prevent a short circuit melting you wiring).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 51 ✭✭✭✭
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Re: I'm ask this question

thank you for the info about the battery set up
• Solar Expert Posts: 226 ✭✭✭
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Re: I'm ask this question
henry1 wrote: »
First off Sorry about that ..I was trying to times the batties by the number of ten to make a total single string of ten batterys in the string and yes that one the huge 12V 225ah batties that way 150.pds each .

I would like 10 each of those batties in each of the battie strings for use on the cabin design ..

10 batteries in each string? How many strings are you going to use?
Why so many batteries for a cabin?

Probably a lot cheaper to reduce your power consumption and then use a smaller solar setup.
• Solar Expert Posts: 51 ✭✭✭✭
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Re: I'm ask this question

The basic idea was to make the bank last a week before switching over to a new bank with new bank was recharge dureing the week with solar and wind or gen set if need ..
• Super Moderators, Administrators Posts: 33,479 admin
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Re: I'm ask this question

The problem is that Lead Acid batteries do not like to sit for days/weeks below 75% state of charge.

If you discharge a bank to 50% and recharge back to 100% the next week--I would fear that your batteries are going to die a few years early from sulphation (the soft lead sulfate that participates in the recharge/discharge cycle begins to crystallize and no longer is in the charge/discharge chemistry--slowly reducing the battery capacity.

Lead Acid it probably the wrong chemistry to use in this type of setup...

There are other chemistry's that do work (NiCad, Lithium Iron Phosphate Batteries; LFP; LiFePO4) (and others?) that would work--but they are probably 2x more expensive and, in the case of NiCad can be expensive to properly recycle/dispose of...

My guess is that a small genset (fuel efficient) is going to be a better/more cost effective solution unless you are ready to go "out there" with other battery chemistry.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 226 ✭✭✭
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Re: I'm ask this question
henry1 wrote: »
The basic idea was to make the bank last a week before switching over to a new bank with new bank was recharge dureing the week with solar and wind or gen set if need ..

No, no, no, no, NO!

That is NOT the way to set up your batteries.

To get the best life out of Lead-Acid batteries, drain them as little as possible and recharge them as soon as possible.

You don't use one battery bank while charging a different one. You use ONE bank and charge it every day. You can charge the bank while using power.

What you need to do is figure out how much energy (kwh) you need on an average day. Then you find out what the worst case charging will be, for example if 4 day storms are common there, then you'll need to run about 4 days without being able to charge or not much charging) so you size your pack to provide 4 days of power while only using 80% of capacity.

Using only 20% of your batteries capacity on an average day will ensure maximum life from your batteries.
• Solar Expert Posts: 51 ✭✭✭✭
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Re: I'm ask this question

I'm going to turn down the job and focus more on the small system of the place in Northern Az area up on the Four Corners Area to make it my retirement place