WB4SON

After “fully” charging the battery, I put it into service during a POTA activation.  Imagine my surprise when 10 minutes into the activation my radio shut down.  I suspected a battery failure, but didn’t have a backup with me.

When I returned home, I discovered the battery was producing 0 volts, exactly as if the BMS had shut the battery down.  My reasoned guess is that the battery cells were not balanced, resulting in a protective shutdown.  So I “fully” charged the battery again, allowing it to stay on charge for about 4 hours.

I set up a test with a 6 Amp draw to check on the battery capacity this afternoon.  Just like during the activation, the battery was fine until about 12 minutes into the test, when it simply shut off after supplying about 1.2 AH to the load.

My suspicion is still that the battery is badly out of balance, and many hours of “trickle” charge are going to be required to restore operation.  But it is entirely possible that one of the cells has failed.

Note, this battery sat unused in my house (so room temperature) for about 5 months after being fully charged.  It was not abused in any way, and had less than 100 cycles on it, never drawing more than 50% capacity.  The battery itself was produced in late 2021 so it is about 2.5 years old.

Back in 2020, I purchased an inexpensive 16 AH LiFePO4 battery from Amazon, made by Miady.  Initial testing indicated that it was optimistically specified, as it tested to be 15.24 AH, but that wasn’t bad given it was about a third the usual price.  I wound up using that battery as my primary power source for many POTA activations over the next two years.

The last time I charged it was on December 20, 2022.  Giving it a full charge this morning, I found that 0.357 AH was required.  So the battery had self-discharged 0.357/15.24 or 2.3% over a period of 158 days.

Just goes to show how low the self-discharge of a LiFePO4 battery is – about 5% per year!