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Are these cells balanced?

PeterH

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Joined
Nov 16, 2019
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In 2012 I bought 45 CALM 130Ah Lithium Iron Phosphate cells for a DIY EV. After 16,000 miles, the EV is long gone but the cells remain. I’ve been using them as 12 V batteries in my camper and they work well. But sometimes they get out of balance, one cell goes high and shuts off the charging, isolating the battery from the rest of the system.

Now that it is winter and the camper is in storage, I am rebuilding all of my batteries, starting with testing their capacity so I can be sure to have matched cells in each battery.

These first 4 cells were tested with a MakerHawk Electronic Load Tester as seen on Will’s channel. I limited the test amperage to 10 amps and set the cut off voltage at 2.7 volts as measured at the tester. The ending voltage seen in the table below, were measured at the cell terminals.

While I want to use balanced cells, I’m not 100% certain I know what that means. These 4 cells were top balanced at 3.6 volts when arranged in parallel. They rested for a week before I started testing.

Cell Number:Starting Voltage:Ending Voltage:Amp Hours Measured (10Ah draw rate)
173.5432.937122.21
223.5552.962122.33
413.5722.99120.34
42(forgot to measure)118.08

With another 39 cells to test, I think I need to find a faster testing method; this is taking 24 hours to discharge and charge each cell.

Thanks for your thoughts on this!
 
Last edited:
Faster means more Amps on discharge and Charge. I use a Revolectrix PowerLab 8 that can handle up to 40 Amps at 3.5 volts. It can automatically go through a charge and discharge cycle and log the results. It needs a separate power supply.
 
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