I think this is capacity test #6. Another desirable outcome.
8 Xuba 3.2V 280Ah cells (24V nominal) - Rated capacity 7,168Wh
I set the Inverter/ Charger to 27V charging. Rested over night to 26.80V.
Test Range
Upper limit: 26.80V (rested voltage)
Lower limits (varying low C-rate loads):
25.24V, 5,833Wh = 81% usable capacity
25.27V, 6,253Wh = 87% usable capacity
25.52V, 6,444Wh = 89% usable capacity
1st Pic - Test Begins, Inverter off, battery rested all night.
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2nd Pic - Inverter powered on. The 3 voltage readings show slightly different from one another.
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3rd Pic - Powered stuff on, coffee maker & home office stuff. Noticed 2V drop right off the bat. Something to factor in when considering range usage.
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4th Pic - 81% usable capacity
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5th Pic - 87% usable capacity. Met 85% goal. Shut everything off soon after. Bedtime.
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6th Pic - Battery rested over night. About a 0.41V recovery. Inverter off
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7th Pic - The next morning, out of curiosity, I ran the coffee maker again to see if the battery's lower voltage would drop so much to trigger inverter cut-off (shutdown). It held up.
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8th Pic - Finished brewing coffee. Inverter off. Ended test. Overall used capacity, about 89% @25.5V.
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I did a similar test about a week ago where I charged the battery to 26.80V, but I set the charger to 26.80V, let the battery rest a bit, the voltage would drop, I'd charge it again, let it rest, the voltage would drop, charge again, etc... Did this numerous times and kept trying to stabilize the voltage to 26.80V. Still dropped. The best I got it to was 26.76V without wasting another day of fussing around.
The difference this time was I charged to a higher 27V then let the battery rest to 26.80V. Got a much better outcome this time compared to
before.
So, it looks like a range of 27V - 25V is looking pretty reasonable to allow for some voltage fluctuation (charging, resting, under load) and still get a decent usable capacity of 80% - 90%.