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

[Isaac-1]

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.

 

[HOU_Castle]

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]

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]

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]

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]

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.

 

[Azycray]

Time to revive this thread. I have 4 new Litime 12v 230Ah batteries I plan to use in series. I initially charged them and here is what concerns me, two are 13.35v-13.4v so no problem there. The other two are 12.88v, that concerns me. I have read not to be too fixated on voltage, it's really the capacity that matters since LiFePo has such a flat voltage range. So, I have a smart shunt arriving today, should I do a capacity test of all 4 batteries to see what their respective capacities are? How far apart is acceptable between 4 batteries that will be used in series? After I drain them, should I connect in parallel and recharge before wiring in series? And any other advise for my situation. Thanks

 

[wpns]

Time to revive this thread. I have 4 new Litime 12v 230Ah batteries I plan to use in series. I initially charged them and here is what concerns me, two are 13.35v-13.4v so no problem there. The other two are 12.88v, that concerns me. I have read not to be too fixated on voltage, it's really the capacity that matters since LiFePo has such a flat voltage range. So, I have a smart shunt arriving today, should I do a capacity test of all 4 batteries to see what their respective capacities are? How far apart is acceptable between 4 batteries that will be used in series? After I drain them, should I connect in parallel and recharge before wiring in series? And any other advise for my situation. Thanks

What are your plans for inter-battery balancing?

 

[Azycray]

What are your plans for inter-battery balancing?

I wasn't aware of any options while in series. But once or twice a year I could unlink them and wire in parallel and charge them.

 

[wpns]

Look for battery balancers, I don’t know much about them but know they are nessesary(*) for batteries in series.

(*) Yes, charge in parallel on occasion is also an option, depends on how quickly they diverge and what your tolerance for rewiring is.

 

[Azycray]

Look for battery balancers, I don’t know much about them but know they are nessesary(*) for batteries in series.

I searched, there aren't many options out there for an apparent demand that needs to be filled. The one model that looked like it was purpose built for balancing in series batteries was being sold by more than one vendor. Re-branded but all obviously made in the same factory, or at the very least, to the same design dimensions. But I found it for sale by the same manufacturer that made my batteries, so that is where I purchased it. Just thinking warranty claim down the road if this balancer doesn't work. We shall see in good time what I think of it, but the positive reviews were the majority. It only runs on 5 amps but this is not a bulk charger, it only needs to move excess energy from one battery to another. So even though the batteries are 230Ah, it doesn't need more than 5 amps to balance the difference of half a volt. Now granted, with a very flat charge curve, .5 volts at 5 amps could take several hours. That's fine, once it gets in balance it will keep it that way for an acceptable loss of watt hours. This "should" solve the imbalance of my batteries.

 

[Azycray]

FWIW, if you read my first post you can see the volts of the batteries after initial charging. I just wired them in parallel but checked them before, one was still at 13.3, the other 13v dropped to between 12.86v and 12.88v with the other two. By the time I had wired them up in parallel and put the meter back on them the bank was 13.3v, everywhere. It didn't matter where I put the probes between any of the + and any of the -, every reading was 13.3v. I did not expect that. Not just the time or speed it took, and I don't know if they are truly balanced or just looking like they are. But I would have expected the bank to drop towards the middle volt range of the 4, not the lower 3 to rise up to the top voltage. So I'm actually feeling a little better about the spread in voltage between the 4 brand new batteries. It will be realistically another 2 weeks before I am finished with the install. I'll probably check the bank voltage in about a week and possibly do a capacity test in 12v with a smart shunt and then charge them in 12v before I wire them in 48v. I want to see what the shunt says the capacity is. Then I may do another capacity test in 48v to see what the difference is, adjusting the numbers for the voltage change.