Testing AGM batteries?
When I got my last set of batteries (150aH AGM, used), they had been tested on a high-amp car tester. But my friend who knows batteries pretty well said that was not a proper test, that what we shoul...
Forum Discussion
I judge battery performance with an AH counter often rezeroed when it is known the battery is indeed full as full can be, and voltage held for AH removed under a certain load and a big helping of trends and tendencies.
My current AGM is still causing some head scratching, as in November it will be 3 years old. It has about 350 deep cycles on it anbd a couple hundred more shallow cycles, and a few thousand engine starts on it, yet under discharge it is maintaining the same voltages under the same loading as it did when new but I rarely take it below 50%, and Mex once said this is where the lost capacity will be much more noticeable, voltage held wise.
Its degradation has only been noticeable in that it has lost some of that supremely violent quick engine cranking ability, and when new it could easily suck 100+ amps at ~50% depletion, now absorption voltage can be reached at ~75 to 80 amps at 50% depleted.
It is a 90AH group 27 Northstar AGM, and it continues to impress me. But it needs that high amp recharge applied from its most depleted state every so many deep cycles or performance tanks noticeably on cycle number 4 or 5 of low and slow solar only recharge to full.
Too many deep cycles without a high amp recharge and then it requires less than 50 amps to reach absorption voltage almost immediately and amps begin tapering almost immediately, and then it takes forever for amps to taper to 0.5% of capacity at absorption voltage.
So too much low and slow recharging after back to back deep cycles means much longer recharge times and increasingly so, even if a stronger amperage charger is used.
While the lesser $$ AGMS say no more than 30% charge rate, I believe they will still benefit from charge rates up to this level. My Northstar, like Odyssey and Lifeline AGM have no really easily achievable upper limit on charging amps, and My Northstar appear to be happier than a pig in feces whenever I can feed it 40+ amps from 50% to absorption voltage.
Holding absorption voltage until amps taper to 0.5% of capacity is just as important, but both the high amp and the taper to 0.5% of capacity at absorption voltage is the key to maintaining performance, In my experience with it, with a AH counting battery monitor at my right hand and an interest in the subject, and the desire to experiment and see the results.
The surplus tellyCom AGMS seem to have some different needs than the regular Usual suspects in the AGM world, and my statements are not meant to apply to those.
My current AGM is still causing some head scratching, as in November it will be 3 years old. It has about 350 deep cycles on it anbd a couple hundred more shallow cycles, and a few thousand engine starts on it, yet under discharge it is maintaining the same voltages under the same loading as it did when new but I rarely take it below 50%, and Mex once said this is where the lost capacity will be much more noticeable, voltage held wise.
Its degradation has only been noticeable in that it has lost some of that supremely violent quick engine cranking ability, and when new it could easily suck 100+ amps at ~50% depletion, now absorption voltage can be reached at ~75 to 80 amps at 50% depleted.
It is a 90AH group 27 Northstar AGM, and it continues to impress me. But it needs that high amp recharge applied from its most depleted state every so many deep cycles or performance tanks noticeably on cycle number 4 or 5 of low and slow solar only recharge to full.
Too many deep cycles without a high amp recharge and then it requires less than 50 amps to reach absorption voltage almost immediately and amps begin tapering almost immediately, and then it takes forever for amps to taper to 0.5% of capacity at absorption voltage.
So too much low and slow recharging after back to back deep cycles means much longer recharge times and increasingly so, even if a stronger amperage charger is used.
While the lesser $$ AGMS say no more than 30% charge rate, I believe they will still benefit from charge rates up to this level. My Northstar, like Odyssey and Lifeline AGM have no really easily achievable upper limit on charging amps, and My Northstar appear to be happier than a pig in feces whenever I can feed it 40+ amps from 50% to absorption voltage.
Holding absorption voltage until amps taper to 0.5% of capacity is just as important, but both the high amp and the taper to 0.5% of capacity at absorption voltage is the key to maintaining performance, In my experience with it, with a AH counting battery monitor at my right hand and an interest in the subject, and the desire to experiment and see the results.
The surplus tellyCom AGMS seem to have some different needs than the regular Usual suspects in the AGM world, and my statements are not meant to apply to those.
