Beginner Questions

[jeff88]

I am working on my solar/battery project and have a few initial questions regarding the battery.

1. Can I use any Lifepo4 battery off Amazon, eBay, Alibaba, etc.? I know some of the inverters have specific brand batteries they work with. Is there a reason to not use something "off-the-shelf"?
2A. Is there any reason to use (1) 48 volt battery at a specific size (say, 100Ah) vs. (2) 24 volt batteries of the same size in serial? Besides physical space and wiring, is there an advantage to either?
2B. Same for the capacity - is there a benefit to having (1) 100Ah battery vs. (2) 50Ah batteries in parallel?
3. If the rating of the battery is 100Ah, but the standard max usage is 80% does that mean that I have an 80Ah battery, or is the battery actually something closer to 125Ah and I'm using 80% down to 100Ah so I get the full rating of the battery?
4. Rack mount vs. vehicle battery - does it matter for my purposes?
5. If I get a rack mount, can I use any 'ol server rack or do I need something specific?

 

[sunshine_eggo]

1. Are you complying with local regulations? If "yes", then "no". If compliance is not a concern, "yes." CA requires UL certification of batteries, and they must be on their "list."
2A. Yes. A single battery with all cells monitored by the same BMS will maintain cell balance better.
2B. Yes. Same as 2A - two separate batteries may not share current equally and may be out of balance with each other. This is not a deal breaker, but it should drive your decision.
3. It means it's a 100Ah battery that they recommend you use no more than 80Ah out of it.
4. I don't see that you've disclosed your "purposes."
5. Dunno. Many just set them on the ground or stack them or buy a fancy custom case for them.

 

[jeff88]

Thanks for the reply.
1. What is the UL listing I am looking for?
2. If I want to start small and add more battery capacity later, are there BMS options that act as if it is one battery?
3. Understood.
4. By my purposes, I just meant putting them in the garage along with the other equipment, nothing special.

 

[sunshine_eggo]

1. UL1973 for starters and maybe UL 9540 and UL 9540A depending on system design. Whatever, the case, CA requires use of only specifically approved components, i.e., somewhere they have a list. If the device isn't on it, you can't use it, even if UL listed.
2. Batrium. Server rack batteries with BMS capable of communication between batteries and AiO units.
4. Still not enough to go on.

 

[jeff88]

What other information would I need to decide if a rack mounted or sitting on the ground solution would be required?