Re: [electricboats] Cells seem to have stopped increasing voltage when balancing

Peter.

You're balancing a batch if cells identical to the ones I recently finished capacity testing, recharging, and balancing as my new pack.

My ThunderStruck chargers and related monitoring gear were already installed on the boat, so on my test/work bench at home, all I had to use to recharge each cell after drawing it down were a 300 watt variable voltage power supply, and a 12vdc, 30 amp Lipo charger.

My target pre-install balance voltage for each cell was 3.55v starting from just under 3.00v.

My work flow for each cell was to do a discharge test (end state of ~2.7v recovering to ~3.0v) and use the variable power supply to bring the cell up 3.2v or so while the next cell was being discharged.  As each cell completed that cycle, I connected it in parallel with the previous cell such that I had 4 cells at roughly the same 3.2v.  After the four cells had some time to balance to one another (checking each cell with a good multimeter), I reconnected them into 12v series and attached my 30amp, 12v Lipo charger.  The 30a charger pumped more watts per cell than my 300 watt variable power supply could.

Once the cells were just over my target voltage, I took the 4-pack apart and reconnected them in parallel once more.  The next 4 cells went the same way, then I had 8 cells in parallel at my target, and so on thru the 16 cells.

If you don't have access to a 30+amp charger running at 48+volts, and are limited as I was to a low-watts power supply, or a 12v 30amp charger, then grouping them into 12v packs can take less time.

Whether discharging or charging, these cells will sit at around 3 3vdc for most of the cycle.  The like all Lipo cells, the discharge curve is quite flat between about 15% SOC and 90% SOC.

It's important to closely monitor each cell individually while charging to avoid exceeding 3.65v.  Once they get to ~3.55v they can climb pretty quickly to max allowable.

The equipment you're using is different than mine, and it seems youbare starting from a higher SOC for each cell than I was in my process.  So you'll have to make appropriate adjustments.

Be safe; have fun!!

[-tv]

 

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