Are these lead acid batterys suitable to build a powerwall with?

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multiboxer

New member
Joined
Sep 21, 2021
Messages
5
Hello everyone,

I wondered if I could use the following batteries to build a power wall with and hook them up to a fitting MPPT charger+inverter and solar panel setup. (Victron Easysolar)


Type : 6EP1935-6MF01 (datasheet attached)
Amount : 600+
Age : 3 years max
Voltage : 24V packs
Cap : 12Ah / 0.28kW/h
Always stored between 15-25°C
Always connected to a charger/UPS system
Been partially discharged maybe 4 times.
The battery impedance/voltages would be checked beforehand to weed out any bad ones and make sure they have the same voltages.
I would start the setup with 64 of these and hook them all up in parallel to the MPPT.
That would give me 18,4kW/h of power which I can of course only partially discharge.

What do you think of this setup with (quite a few) smaller batteries?
I can even expand the battery setup as I have plenty more available over the next years.
The fact that I can get them for free makes it very tempting to give it a try.

My apologies for my English, it's not my first language.
Thanks in advance for the advice!

Multiboxer
 

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Oberfail

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Jun 22, 2021
Messages
103
The fact that I can get them for free makes it very tempting to give it a try.

Thats quiet a deal when you get them for free.

However as they are already used since 3 years, they probably wont have much life in them left. As by the manual, the service life is only 4 years if the battery is being kept at 20°c, after that it only has 80% capcity left which is falling quickly. You also need make sure, to ventilate them well with fresh air, as lead acid batteries vent gas when being charged. And the technology to keep all the cells in-check is rather hard to find, since most people use lithium batteries.

I'd rather try to find a different source of batteries if possible, but they can still be used if you want to.
 

Oberfail

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Jun 22, 2021
Messages
103
Yeah found that out myself, too bad you can attach measurement cables to each individual cell inside them :/
That would help well with keeping them alive for longer.
 

italianuser

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Feb 25, 2020
Messages
376
Lucky man (if batteries are still good)!

If I just imagine me mounting all those batteries, I think I'd begin with seeing what kind (and how many meters) of cable is needed. After that I'd need something for monitoring the batteries, maybe those little voltage screens: https://it.aliexpress.com/item/32801788262.html

It's important you're able to monitor the system for any battery that might die or go low on voltage.

P.S.
Load the photos using the "Attach" button you have right under the posting box!
 

Korishan

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Jan 7, 2017
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6,573
If I were to do something with these kinds of batteries, I would run a bus bar alone the wall with a bunch of leads coming off to connect to each battery. so each pigtail would only be about a foot long, or shorter if possible. And go with 14 awg.
Monitoring each battery would be tricky, though. The only "real" way to do so would be each battery would need to have its own shunt monitor. If getting premade, this could be costly. Altho, you can buy the shunt sensors individually pretty cheap, and then use an arduino or other mcu to monitor the voltage drops.
For instance, on Aliexpress, you can get them for <$1USD + s/h, but you can buy a batch of them for same shipping.
 

ynot

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May 28, 2021
Messages
64
Have lived off grid with Lead Acid batteries for a total of 18 years, plus having RV.s and living off grid for months at a time since 1976, we may be able to offer some advice based on experience.
Since the batteries if stored fully charged and only partially discharged 4+/- times, the batteries will be in like new condition. They should not have sulfated, which is the LA batt killer. If you have enough of them that they will not be discharged below 50% capacity and will be recharged as soon as possible to full or close to full they will last for years. When you are figuring out how many batteries you need in parallel, divide the rated amp hours in half, so for your batteries you should aim for a maximum of 6AH draw down per 12volt batt.
Unlike lithium batts., they need to be kept as fully charged as possible in order to keep them from building up sulphates and eventually dying.
Korishan's idea of using bus bars when possible is a good one, just build a series parallel array to get the voltage/amperage levels you want, connect em up and enjoy.
Sealed LA batts do outgas but not as much as the older flooded type, so you do need to pay attention to outgassing, but should not be too worried about having a problem.
I believe there is no simple/practical way to monitor each cell or even each battery, you could possibly put a cheap ammeter on the positive terminal of each battery in a parallel array, then notice if any battery is delivering fewer amps than it's sisters, but why bother?. I would simply set aside a day every year to check each battery with a low cost resistance tester available at auto parts stores, you would not even have to disconnect the batteries to do it. PS. do not over test with a resistance tester, as it is hard on the batteries.
 

Redpacket

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Feb 28, 2018
Messages
1,330
I'd also give some careful thought to the weight of them in a powerwall & the structural load on the wall/floor, etc.
If SLA's do gas, they will quickly dry out & fail - you should operate them ensuring they don't gas, eg reduced equalisation/absorbtion vs flooded.
SLA batteries like these seem to "just age" aka the alarm & UPS industry, even if the batteries have apparently barely been used & kept on float, they may not last well.
That said, free is hard to ague with! :)
Hope they do work out.
 

paddy72

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Nov 17, 2021
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I dont see any severe problems in using these batteries. If they are only 3 years and have never been deeply discharged these sealed Lead-Acid batteries should be good to go!
The worst enemy of LA is to deeply discharge them and keep them in discharged state for longer period. Then hard sulfation will take place and cover the plates so that they won't be able to contribute to currentflow. Always charge them fully up as soon as possible and never discharge them lower than 60% SoC (for a 12V LA battery this is around 11.2 - 11.0 V ).
With some care these can live up to 8..10 years but with a max. of around 1000 cycles.
 
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