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SLAs for small home battery bank?  RSS feed

 
Mat Smith
Posts: 125
Location: Gold Coast Hinterland QLD, Australia
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Hi Steve,
so I listened to your podcast on TSP (001 tsp-01039-harris-on-emergency-home-power-battery-backup-show-1-of-2-show14-32k) on the way to work this morning, will listen to part 2 on the way home this arvo

My specific question here is to do with SLA batteries for a battery bank.
I know you covered this a little in that podcast but I’ll tell you my situation and see what you think.

Through work I have access to lots & LOTS of 12V 7Ah SLA batteries from UPS systems.
These batteries are in medical equipment so:
1. The batteries are very new when 1st installed (normally 6 months or less from manufacture).
2. They are on charge 24/7 and very very rarely do they ever get loaded and discharged at all.
3. They are replaced every 2 years, so they are quite ‘young’.
4. I also have a battery analyser at work that I can do a full charge and discharge on to confirm the actual capacity, so I can weed out the dead ones
Currently I have about 40 of these at home so around 280Ah worth of batteries, and access to a lot more.
I also have access to lots of free mini Anderson Plugs like these:

They are on some of the medical batteries, and they just get thrown out so I have been stocking up on them.

My idea was to have most of the batteries connected in parallel via some 150A busbars, like this (or bigger ones):

some inline fuses and no intention of being portable.
Then I was looking at having a few for hunting, camping, portable etc, then when I get back home or have finished with them, charge up, then connect them back up to the home battery bank system.

The plan would be to have the entire system hooked up to a 3 stage charger so they are charged and ready to go.

Interested to hear feedback and ideas.
Thanks

Mat
 
Steven Harris
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I think you got it 100% perfect, I can't hardly say a thing. I DO NOT suggest people put fuses into battery banks at all... NONE... especially between the battery and the inverter. The inverter is already fused internally and it has its own safety circuits. Fuses do only one thing, blow when you don't need them to blow and then you are stuck with a dead system because most people don't have replacement fuses.

I would also NOT take batteries out of the system, go camping, then bring them back, when you put a low battery on a bank of high batteries there is a sudden current dump into that battery and SLA batteries do not like to be charged fast, they have poor heat dissipation. So keep a set of them to go camping, and then keep the big set for your battery bank.

Also..use the tool at work to 100% discharge them (hurts them a little bit) and then charge them back up, that way you know that they will work and what their capacity is.

Steve
 
Mat Smith
Posts: 125
Location: Gold Coast Hinterland QLD, Australia
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Thanks Steve, good to know I'm on the right track.

If I were to remove a battery to use remotely I would charge it back up before connecting to the bank. Maybe like you say though I just keep them separate.

Good point on the fuse - I'll stick with a circuit breaker if I need to. I currently have a small bank of SLAs set up for my led light strips in my mushroom growing room, so no inverter hooked up at the moment, but plan to once I up the size of the battery bank.

The battery analyser does do a full discharge at a rate of 0.1C. It works great - I grab a pair of used batteries from the pile, wack them on the analyser, then come back 24hrs later and I have my results Occasionally there are some 24Ah SLAs - when I find them I set up the analyser at work on the Friday, then come back on Monday morning and have my results, plus a pair of nicely charged batteries

Thanks for you time and knowledge on here Steve, it's much appreciated!
(I'm up to the 3rd of your podcasts now - great info!)
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