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Old 03-20-2019, 03:31 PM   #1
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LiFePO4 capacity test

18 months into usage of a 600 ah 24vdc Lithionics bank consisting of two 300 ah batteries. Probably should have done this when new, but I just finished a capacity test, the results of which may be of interest.

1. Charged bank to 29.4 volts to trigger cell balancing, which I had never done before. Generally I stop charging around 28.2 volts.
2. Placed a 23 amp load on the bank via ship's lights
3. Next day I got tired of waiting, so increased the load to 58 amps for a couple of hours via a portable heater.
4. Verified that the draw being measured was the same on the Link 20 and Balmar SG200.
5. At 90% Depth of discharge, still measured 24.9 volts
6. Stopped discharging at 96% DoD and 24.1vdc. Pretty sure I could have taken out 600 amps if I slowed the draw a bit.

Not so sure about the accuracy of the SG200, as it indicated 100% discharge while the batteries were still at 24.5 volts. State of Health is at 89%. Both measures are clearly wrong, unless the Link 20 coulomb counter is wrong, which is unlikely as the number of hours the test took times the draw is very close to the measured amps consumed shown by the Link, plus both Link and SG200 agreed an the current draw.

These batteries really are amazing, and perhaps the SG200 will get in since with reality after a few more charge cycles. It only has about 4 to work with right now.
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Old 03-20-2019, 05:37 PM   #2
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Update on the SG200. In conversation with the extremely helpful folks at Balmar, I think because of the lack of cycles, plus the size of the chargers used, the SoC reading shouldn't be relied upon quite yet until the unit has a chance to learn. I should be able to get those additional charge cycles under its belt soon, and will provide the data to Balmar in case it is helpful to them to perfect their algorithms to better reflect my use case.
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Old 03-20-2019, 06:35 PM   #3
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Thanks for the update.
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Old 03-21-2019, 12:46 PM   #4
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Thanks for posting your tests. I am considering Victron and Lithionics for my new-to-me boat. I had Victron on my previous boat, and did a similar test and got 296 AH out of a 300 AH battery. Pretty amazing technology....
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Old 03-21-2019, 12:58 PM   #5
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Thanks Delfin
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