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Old June 22nd 18, 05:30 AM posted to rec.aviation.soaring
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Default A complicated question about LiFePO4 batteries, - and switching.

On Thursday, June 21, 2018 at 4:12:09 PM UTC-7, SF wrote:
I started off with two K2'S I charged RIPthem in parallel, discharged them in parallel. No issues. Then one of the cells died in one of the batteries. Ran them in parallel on the test rig current meters on both. The good battery ran the load until the voltage dropped and then the battery with the bad cell started sharing the load until I stopped the test when the voltage dropped under 11V. There was never current flow from one battery to the other. It was all 0 current or current supplied to the load.

Now running two starks in parallel, discharge and charge. No issues in 2 years now.

Fuses on each battery, separate switches for each, each battery's connection to the bus is also fused.

Don't need to make this complicated. But you can if you want to.


The way you would have a problem is if the batteries are in a very different state of charge when they are paralleled. If always charged and discharged in parallel, this can't happen under normal use. If one suddenly developed an internal short, then the other would dump current into it.