New pair of 200AH batteries, what to do first?

Isaac-1

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Nov 4, 2021
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This may seem like a basic simple question, but I can't find the answer anywhere here.

I just received my first pair of LiFePo4 batteries, a pair of 200AH ReBel batteries with 100A JDB smart BMS with bluetooth (a pair from their discounted mis-manufactured batch (wrong BMS 100A vs 150A installed).

My question is what to do before installing and using them, should I, discharge them, top them off (or vice versa) do a capacity test, etc? I do have a 5A CC/CV bench power supply and a good Fluke meter, and will be getting a cheap $20 PZEM-015 style 200A shunt meter in the mail tomorrow. Just waiting on wire and another Renogy DC-DC MPPT charger before installing them in my motorhome, first one from Amazon was broken.

Thanks for your help.
 

NOLA_Castle

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Are these out of the shelves LFP batteries? if yes, you may want to top them off. To wake the batteries up from long storage/hibernation. Then, you can do 0.1 capacity test then, completely charge them up. Make sure, you have the correct wire size, fuse, etc.
 

Isaac-1

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Nov 4, 2021
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Yes, sealed plastic box, drop in 12V 200AH batteries, so no access to the guts, Bluetooth BMS app reports 199.9AH current capacity on both
 

JWes

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Dec 27, 2021
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Good question, I'm still not clear on exactly what we should be doing with new batteries... Top balancing, bottom balancing, capacity tests, gear needed to do all of that, what to do when balancing and capacity test fail... feeling overwhelmed
 

MisterSandals

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I'm still not clear on exactly what we should be doing with new batteries... Top balancing, bottom balancing, capacity tests, gear needed to do all of that, what to do when balancing and capacity test fail... feeling overwhelmed
Top balancing mostly refers to working with individual cells and wiring them in parallel to get all the cells to the top at the same time. Bottom balancing is not useful for solar, mostly electric vehicles. Capacity tests are mostly a waste of time - it says the capacity on the side of battery right? Do you really want to beat the crap out of it to see if you can replicate that test?

Does your battery have a BMS that allows you to see the voltage of the individual cells? If so, what are the voltages when you charge it up? Are they similar? If you cannot see the individual cells, there is nothing you can do other than use your battery.
 

meetyg

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Jun 4, 2021
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If you plan to use these in parallel:
First check thier voltages. If they aren't to much apart (say ~20mv) you should connect them in parallel to each other (without loads) and let them sit like that for a few hours.

Then fully charge them up, using a proper Lifepo4 charger, while still in parallel.

After that they are ready for use.
If they are too far apart, you could either charge the lower one, or discharge the higher one, until they are closer in voltage.
After that you can connect them in parallel and fuly charge as above.

All this is to ensure that they will be at the same SOC when in use, so that the loads will be equal on each battery (50% on each).
If one is at a lower SOC, the BMS will give up earlier, and the other battery will take all the load. Then that battery's BMS might go into a protection mode, because of the higher load (depending on the load, let's say 200A).

The reason you want the voltages to be fairly close, is just so that there won't be a high potential between them, and then hundreds of amps can flow from one to another when connecting in parallel, which again could cause problems.
 
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