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Big batteries - best practises?

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bitSmasher View Drop Down
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    Posted: 17 October 2017 at 9:44pm
I've aquired a few 12V SLA, rated 60 to 80ah, as a step towards building a decent sized battery powered rig.

I know the answer is usually "if you don't know, don't do it" but what are some tips for storing, charging and using these?

Have a smart charger already, intend to use 50A Anderson connectors everywhere and have circuit breakers (DC specific) on each battery.

One thing that I question, is connecting them parallel... is it OK to just bring them to the same voltage and connect together? Or is there some sort of protection that could be used to prevent potential voltage differences causing problems?
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valve head777 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valve head777 Quote  Post ReplyReply Direct Link To This Post Posted: 17 October 2017 at 10:10pm

Ok,
1, the batteries should all be the same AH rating, especially if used in strings.
2, assuming they are, charge them all and let them rest for a few hours.
3, connect them in a string. Same with parallel, volts need to be equal first.

SLA batteries need to be kept charged. Any much bellow 12.40 volts at rest is when sulfation will start.
If you have gel or agm batteries, charging end voltage needs to be well regulated, gel no more than 14.4 max, agm 14.8 max. Flooded as high as 15 Volt's to get good gassing and therefore mixing of electrolyte.

Discharge no lower than 11.90v  (resting voltage)per battery for good life span


Edited by valve head777 - 17 October 2017 at 10:12pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2017 at 12:07pm
Mixing batteries of different types/ages is less than ideal. In parallel, and if age/type/use history more or less the same, it should be fine. If not, then the weaker batteries will pull the better ones down.

If you only use the combined bank for discharge and take it all apart and charge the batteries separately that should be minimised though.

Capacity doesn't matter unless you are connecting in series. Don't connect different batteries in series!

https://www.homepower.com/articles/solar-electricity/design-installation/ask-experts-batteries-series-parallel


http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
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bitSmasher View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 18 October 2017 at 9:48pm
Excellent, it seems fairly straightforward...
Have been given 4x 80ah, all brand new.
Intend to charge separately and then connect parallel.
Have read about protection diodes but don't want to complicate things - hopefully the breakers are enough to stop things going flash and bang
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valve head777 Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 12:40am
IIf you have new batts, you'll want to maximize battery life, so best practices are very important. If used in parallel, consider using a bus bar for connecting them together. Standard practice in ups and solar installation.
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Phil B View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Phil B Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 3:18am
Originally posted by valve head777 valve head777 wrote:


Ok,
1, the batteries should all be the same AH rating, especially if used in strings.
2, assuming they are, charge them all and let them rest for a few hours.
3, connect them in a string. Same with parallel, volts need to be equal first.

SLA batteries need to be kept charged. Any much bellow 12.40 volts at rest is when sulfation will start.
If you have gel or agm batteries, charging end voltage needs to be well regulated, gel no more than 14.4 max, agm 14.8 max. Flooded as high as 15 Volt's to get good gassing and therefore mixing of electrolyte.

Discharge no lower than 11.90v  (resting voltage)per battery for good life span


All this ^^^^^

Plus.... 

Oversize your cabling ( go as big as you can) 
DC breakers on any inputs ( solar , wind , chargers)
Inline fuses on the bank itself 
Isolator switch for the whole bank.

.p.


Mostly harmless.... except if catering is shut.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote biotec Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 10:07am
I would also add that paralleled banks of batteries should periodically be given an equalisation charge to prevent the batteries discharging unevenly. Most good chargers have the ability to do this at programmed intervals or on demand.
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valve head777 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote valve head777 Quote  Post ReplyReply Direct Link To This Post Posted: 19 October 2017 at 4:16pm
II would second this,.the only caveat being that only flooded batteries can be safely equalized, as subjecting agm and especially gel will damage them. Gels are a pain really.
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