Big batteries - best practises? |
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bitSmasher
Old Croc Joined: 23 June 2012 Location: Melbourne Status: Offline Points: 2296 |
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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
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1780 |
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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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carlosdelondres
Registered User Joined: 21 June 2012 Location: London Status: Offline Points: 243 |
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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
Old Croc Joined: 23 June 2012 Location: Melbourne Status: Offline Points: 2296 |
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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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valve head777
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1780 |
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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
Old Croc Joined: 21 November 2004 Location: Melbourne Status: Offline Points: 2322 |
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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. |
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biotec
Old Croc Joined: 07 June 2004 Location: United Kingdom Status: Offline Points: 2932 |
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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
Old Croc Joined: 27 July 2012 Location: East Sussex Status: Offline Points: 1780 |
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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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