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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I have a Trimetric monitor for the AH readings. To measure battery capacity at the 20 hr rate by drawing it down for 10 hours, or when it gets to 50%, you need to know when they are at 50%.
With Flooded batts you can take their SG as your marker. When at 50% by SG, disconnect load and wait till voltage bounces back and settles so you can now use the OCV vs DOD table. It can be your confirmation check with the SG marker. You can then double the AH you got to get what it would be for 100% You also have the time it took. If it took 9 hours to get down to 50%, your capacity is 90% of rated.
With AGMs, you can't get the SG, so you can't really use that method. Lifeline says to use the RC figure and the 25 hr rate for that, and do the full time down to 10.5 volts. No way I am going to do that with my batts! You can't stop at half the time either, since you don't know what the full time would be.
So I am going with the 20 hr rate method and use voltage to mark the 50% level, confirming by waiting till bounce back complete.
It is far from exact, but by doing it the same way each time, you can compare with the previous test to see how much the capacity has changed since then. You can then tell if you need to do something about it or if all is normal.
With Flooded batts you can take their SG as your marker. When at 50% by SG, disconnect load and wait till voltage bounces back and settles so you can now use the OCV vs DOD table. It can be your confirmation check with the SG marker. You can then double the AH you got to get what it would be for 100% You also have the time it took. If it took 9 hours to get down to 50%, your capacity is 90% of rated.
With AGMs, you can't get the SG, so you can't really use that method. Lifeline says to use the RC figure and the 25 hr rate for that, and do the full time down to 10.5 volts. No way I am going to do that with my batts! You can't stop at half the time either, since you don't know what the full time would be.
So I am going with the 20 hr rate method and use voltage to mark the 50% level, confirming by waiting till bounce back complete.
It is far from exact, but by doing it the same way each time, you can compare with the previous test to see how much the capacity has changed since then. You can then tell if you need to do something about it or if all is normal.
