Loaded V vs OCV for DOD Lifeline AGMs ?
Anyone explain this please? They have 50% at 12.15v loaded at the 20hr rate, but say it is 12.18v OCV. Shouldn't the loaded voltage be farther down from the OCV than that? (Appendix in link) h...
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LY, good info. I am doing a re-test of my big 8D 250AH AGM after a disappointing capacity test the other day and a follow-up Lifeline type 8 hour conditioning session at 16 volts. I am part-way through the re-test but so far it does look better. I will post the results.
Yes, one clue something was wrong was the loaded voltage being unusually low for the load.
The 8D has the same OCV vs SOC graph as the one I linked above with a broad brush range of voltages. It tends to be about 13v when full and 12.4 volts at 50% when the battery is in good shape. IE in the middle of the range of voltages in the graph.
I am using 12.4 bounce back to resting as my marker for 50% for these tests. As long as I use the same marker I can tell if things are better or worse, even though the exact capacity measurement might be off in percentage.
Temperature is an issue. If I pick the 20 hr rate according to ambient, I would have a lower rate--
EG, 250AH rated at 25C, is more like 225AH at 10C, so my chosen rate for the test would be 11.25 amps instead of rated 12.5 amps.
But then what about the battery's actual temperature? Does it heat up discharging? It does charging for sure, so if you want to see the in and out AH come out the same except for heat loss on recharge, what to do? It is messy.
I choose to use the 12.5 amps even if it is cooler out ambient, and let it all happen. I figure the real capacity will be a tad higher than what I get from using the higher rate. Main thing is to do each test the same way so they can be compared.
Yes, one clue something was wrong was the loaded voltage being unusually low for the load.
The 8D has the same OCV vs SOC graph as the one I linked above with a broad brush range of voltages. It tends to be about 13v when full and 12.4 volts at 50% when the battery is in good shape. IE in the middle of the range of voltages in the graph.
I am using 12.4 bounce back to resting as my marker for 50% for these tests. As long as I use the same marker I can tell if things are better or worse, even though the exact capacity measurement might be off in percentage.
Temperature is an issue. If I pick the 20 hr rate according to ambient, I would have a lower rate--
EG, 250AH rated at 25C, is more like 225AH at 10C, so my chosen rate for the test would be 11.25 amps instead of rated 12.5 amps.
But then what about the battery's actual temperature? Does it heat up discharging? It does charging for sure, so if you want to see the in and out AH come out the same except for heat loss on recharge, what to do? It is messy.
I choose to use the 12.5 amps even if it is cooler out ambient, and let it all happen. I figure the real capacity will be a tad higher than what I get from using the higher rate. Main thing is to do each test the same way so they can be compared.
