Test results on 12v 100ah lifepo battery? Ran twice
- Thread starter Jmmiller
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chrisski
Solar Boondocker
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- Aug 14, 2020
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If you are capacity testing a battery, different BMSs could cut off prior to the 100% rated capacity, but not at 43% of it.
I would say its bad, provided
1) Batteries were fully charged to 3.65 volts per cell in a top balance (or manufacturer spec)
-and-
2) Discharge cutoff was 2.5 volts per cell.
Please note I have only capacity tested individual cells.
For example, I doubt the BMS is set to a cutoff of 3.65 per cell so probably 3.55 or so, which is 90%+. On the other side, I doubt a BMS was set to a cutoff of 2.5 volts per cell, probably around 2.65 volts, so around 10%. I would expect at least 80%, 80 amp hours, of capcity prior to BMS shut off, but probably more than that. Also, with the BMS there are battery voltage cutoffs in addition to cell cutoffs, but still at least 70%, probably more.
EDIT: I would also add you could check the discharge time with a known load. Should not be as accurate but will double check the reliability of the discharge unit. I have a couple of LEDs and other items that draw 12 volt DC current that I could hook up and test with an amp meter to see how many amps being drown. for example a 5 amp load would last around 9 hours based off the discharge test. If it last well longer than that, the discharge tester is bad.
I would say its bad, provided
1) Batteries were fully charged to 3.65 volts per cell in a top balance (or manufacturer spec)
-and-
2) Discharge cutoff was 2.5 volts per cell.
Please note I have only capacity tested individual cells.
For example, I doubt the BMS is set to a cutoff of 3.65 per cell so probably 3.55 or so, which is 90%+. On the other side, I doubt a BMS was set to a cutoff of 2.5 volts per cell, probably around 2.65 volts, so around 10%. I would expect at least 80%, 80 amp hours, of capcity prior to BMS shut off, but probably more than that. Also, with the BMS there are battery voltage cutoffs in addition to cell cutoffs, but still at least 70%, probably more.
EDIT: I would also add you could check the discharge time with a known load. Should not be as accurate but will double check the reliability of the discharge unit. I have a couple of LEDs and other items that draw 12 volt DC current that I could hook up and test with an amp meter to see how many amps being drown. for example a 5 amp load would last around 9 hours based off the discharge test. If it last well longer than that, the discharge tester is bad.
Given the Ah and Wh shown, it indicates lower than expected voltage at the top end of your discharge.
You may not have a fully charged battery. I have some questions:
At what voltage do you charge the battery?
How long had the battery been resting after charging prior to being tested?
What was the voltage of the battery when you began testing?
What gauge and length of wire did you use to connect the tester?
You may not have a fully charged battery. I have some questions:
At what voltage do you charge the battery?
How long had the battery been resting after charging prior to being tested?
What was the voltage of the battery when you began testing?
What gauge and length of wire did you use to connect the tester?
Thanks everyone for your suggestions!
Used the suggestion on checking wire gauge and that was it. Used the set that came with tester for 1st round of tests. So changed the wire to 10 gauge and redid test and passed with flying colors. Had 1189wh and 100.08ah= Great battery.
Another lesson learned, Wire size matters in your setup
Thanks everyone
Used the suggestion on checking wire gauge and that was it. Used the set that came with tester for 1st round of tests. So changed the wire to 10 gauge and redid test and passed with flying colors. Had 1189wh and 100.08ah= Great battery.
Another lesson learned, Wire size matters in your setup
Thanks everyone
