heirloom hamlet
life my way
Delta, when you say you "charged", was this via utility or PV?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%.
My 32 cells came in and i was able to make 3 24v batteries (24 cells) using cells that were identically balanced of of the boat, 3.301. I had a few more of those, a few that were really close, and then one black sheep at 3.269. I made my 4th battery the misfit one, with the less harmonious cells put together. I tried using Will's little 5a charger, that was going nowhere, so I said screw it and plugged it in...started charging via PV. Just one day of cruddy cloudy weather and she's perfectly balanced on her own. No BMS. But, when charging is removed, and a tiny load is out on, like a 75w fan for a while, that cells seems to always dip quicker.
In fact, when charging stops all the cells do there own thing a bit and get out of balance, only to find there equilibrium again when charging. Do you see similar behavior.
It's crazy that you are getting that much power between 2 volts. It doesn't take much for my 2.25kw array to get them to 27v. I'm going to start running tests using your standards. I have seen nothing that tells me not to. Will talks about 29.2, but man, I don't know what it would take to get these that high. Seems almost impossible.
Quick question...does yours charge alright via 120v utility? For some reason, my LV2424s will plug into and recognize the utility connection, but will not charge these cells. Only PV will. Which is mostly fine, but I can't figure why. Doesn't seem to be a setting issue that I can see and the LV2424s SCC would charge my old BYD batteries just fine. It was a different and probably inferior charge than PV, but it worked on some level.
Appreciate any insight and experience.