Do you have to balance?

[jabbles]

I bought 2 identical 12V 100Ah LiFePO4 batteries

I expect that they arrive from China probably at like ~50% charge


I'm just building a UPS for my computer so I want to hook them up in parallel and connect to my axpert inverter

do I need to balance these batteries before putting them in parallel? or is that only for when you build diy batteries with individual cells
I have a multimeter so I can check the voltage, but how much difference is too much?

I have seen people just connect the batteries to each other and wait 24-48h to let them balance each other, is that fine?

 

[chrisski]

I would charge both batteries prior to hooking together. This will prevent an inrushnof current.

 

[jabbles]

Is there any way to achieve this without a charger? I don't have one at the moment

 

[MurphyGuy]

Is there any way to achieve this without a charger? I don't have one at the moment

Just make sure they are at the same voltage when you parallel them together. Doesn't really matter if they're near empty or fully charged, only that they are at (near) the same voltage.

If you don't have a charger, just put a small load on the high one until it discharges to a voltage that is equal to the other one. You DO need a decent multimeter.

If you're not confident when you connect them, just put a temporary 5 or 10 amp fuse inline.. If the inrush is too much, it will blow the fuse.