AGM vs Flooded Bulk Times
PT keeps asking whether AGMs will spend more time in Bulk at the same charging rate. I found a good example where that can be measured, using ah64id's test with his PD4655 on his pair of Lifeline...
Forum Discussion
Thanks for the additional data. But please confirm your SOC percentages.
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EDIT--morning of 25 Nov:
I am wondering if the batts were really at 49% at the start, where that would be 49% of 220AH at the 20 hr rate, or well below 49% at the 20 hr rate. The initial draw down was at high amps so to know what the actual starting SOC was then, at the 20 hr rate, you would need the resting voltage to be that 12.2ish (no SG measurement with AGMs)
The clue might be the voltages reported once charging began at the 125 amps level. If you hit 220AH Wets at 49% SOC with 125 amps, the battery voltage will "spike" very high so that it will be close to Vabs 14.6 very quickly and amps will then taper right away. You are into absorption already.
In this AGM test, voltage started in the 12s and was only 13.9 after 25 minutes at 125 amps. IMO that could only happen if the batts were well below 12.2 before the 125 amps was applied, IAW well below 49% (20 hr rate) so it spiked, but only into the 12s or low 13s.
So if that did happen that way, then it explains how the results seem to show they got ao high in SOC before amps tapered. Perhaps really the SOC (20 hr rate) was much lower when amps tapered at the 25 minute mark.
EDIT some more---with their lower R, would you get that big spike in voltage when you start an AGM recharge?
OK checked back to the other guy's AGM recharge data, where he did start at 50% 20 hr rate.
Before the start, 300AH batts were at 12.21v , then hit with 56 amps, voltage went to only 12.65 and within 5 min was 13.08.
You would expect more of a spike in this test with 125a on 220AH, but not sure how much.
What think?
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First reply here, where I was using the 20 hr rate for everything and had not remembered about Peukert then:
"I get 49% SOC to be 108AH remaining from 220
Then 25 minutes of 125 amps to be 52AH so that would bring the batts to 108 + 52 = 160/220 = 73% SOC and not the 68% indicated.
(Unless the percentage accounts for heat loss????--which would make that : 68% = 149.6 - 108 = 41.6/52= 80 which would make heat loss 20% which is too high, but at 10% for heat that would be 46.8 + 108 = 154.8/220 = 70% getting closer! )
Or was the time at "125" partly less at first during the "ramp up?"
Even so, it tends to support the results reported in the OP the other guy got with his AGMs and that they start to taper earlier with a higher charging rate same as Wets do.
EDIT, but also that 70ish % SOC for start of tapering is higher than with Wets in this case,(would have been more like 60% or less)
Need more examples for various AGMs and charging rates to get a better picture."
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Yes, to confirm this more we need to be sure what SOC the batts are (at the 20 hr rate) before the test starts.
-----------------
EDIT--morning of 25 Nov:
I am wondering if the batts were really at 49% at the start, where that would be 49% of 220AH at the 20 hr rate, or well below 49% at the 20 hr rate. The initial draw down was at high amps so to know what the actual starting SOC was then, at the 20 hr rate, you would need the resting voltage to be that 12.2ish (no SG measurement with AGMs)
The clue might be the voltages reported once charging began at the 125 amps level. If you hit 220AH Wets at 49% SOC with 125 amps, the battery voltage will "spike" very high so that it will be close to Vabs 14.6 very quickly and amps will then taper right away. You are into absorption already.
In this AGM test, voltage started in the 12s and was only 13.9 after 25 minutes at 125 amps. IMO that could only happen if the batts were well below 12.2 before the 125 amps was applied, IAW well below 49% (20 hr rate) so it spiked, but only into the 12s or low 13s.
So if that did happen that way, then it explains how the results seem to show they got ao high in SOC before amps tapered. Perhaps really the SOC (20 hr rate) was much lower when amps tapered at the 25 minute mark.
EDIT some more---with their lower R, would you get that big spike in voltage when you start an AGM recharge?
OK checked back to the other guy's AGM recharge data, where he did start at 50% 20 hr rate.
Before the start, 300AH batts were at 12.21v , then hit with 56 amps, voltage went to only 12.65 and within 5 min was 13.08.
You would expect more of a spike in this test with 125a on 220AH, but not sure how much.
What think?
----------------
First reply here, where I was using the 20 hr rate for everything and had not remembered about Peukert then:
"I get 49% SOC to be 108AH remaining from 220
Then 25 minutes of 125 amps to be 52AH so that would bring the batts to 108 + 52 = 160/220 = 73% SOC and not the 68% indicated.
(Unless the percentage accounts for heat loss????--which would make that : 68% = 149.6 - 108 = 41.6/52= 80 which would make heat loss 20% which is too high, but at 10% for heat that would be 46.8 + 108 = 154.8/220 = 70% getting closer! )
Or was the time at "125" partly less at first during the "ramp up?"
Even so, it tends to support the results reported in the OP the other guy got with his AGMs and that they start to taper earlier with a higher charging rate same as Wets do.
EDIT, but also that 70ish % SOC for start of tapering is higher than with Wets in this case,(would have been more like 60% or less)
Need more examples for various AGMs and charging rates to get a better picture."
----------------
Yes, to confirm this more we need to be sure what SOC the batts are (at the 20 hr rate) before the test starts.
