Group 27 AGM mid life performance report
My 90AH Northstar AGM battery is now 38 months old, and has accumulated ~465 deep cycles. When I cycle it, generally I consume 35 to 65AH nightly, average about low 40's Since June of 2015 it ...
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I managed to do a deep cycle on my "ordinary" 27 AGMs and recharge profile today, which does have some comparison to the OP's results.
Especially the temperature rise during Absorption is comparable.
I will post this here, but might copy to my AGM adventures thread too.
My 200AH bank was at est 174AH in the 35F/4C ambient as per battery spec sheet on that. Down 80AH by Trimetric before recharge makes that 54% SOC. Used the PowerMax 55 amp ADJ set to 15.2v as equivalent to 14.8v for 77F. Batt V was 12.5 in the zone for 54% by spec sheet.
It did 56 amps constant (56/174 = 32% charging rate) for 25 minutes getting the batts to 14.7v when amps started to taper at about 68% SOC. Batt side temp IR was 8C
At 1 hour- 32 amps, 14.9v, 80% SOC, Batt temp 10C
At 2 hours- 8.5 amps, 15.1v, 86% SOC , Batt temp 12.5C
AT 3 hours- 4.0 amps, 15.1v, 94% SOC, Batt temp 13.5C
EDIT-- The OP's high charging rate didn't seem to make much difference to the SOC when the amps started to taper, because as you remember from my ugly graphs, the curve goes quite vertical at the left so it doesn't do much good to use a way higher charging rate.
BTW plotting that against my old ugly graph with Vectors on Flooded 27s, using the 70a graph (also 32% charging rate) ---
Amps began to taper at 65-68%
80% SOC was reached with amps down to 35amps in the same Absorption time AGM/Flooded ---NO difference.
By the 3 hour mark they are both also just over 90% SOC. NO difference.
EDIT I lowered charger voltage to 13.7 at the 3 hr mark. The Tri showed no amps at all for a while. Yipes! then I realized the battery bank was still higher buy dropping, so no panic. Eventually, the Tri showed charging amps again, but at a lower amps amount. Leaving it there over-night to get to 100% or else I will need a shot of high voltage to get it there. Whatever it needs tomorrow, I can do it.
Obviously it would be better to have more runs at this at more temperate temperatures to be sure, but I am just not seeing the fabled AGM advantage here in fast charging during the Absorption Stage.
I do not have side temps of the Floodeds to compare, but those AGMs sure heat up. 13.5C with 4C ambient is quite a jump.
EDIT-- Forgot to mention that years ago tenbear ( ISTR) was on about whether you should calculate "Full" capacity in AH based on internal battery temp or ambient temp. He thought I should lower the actual charger voltage as actual battery temp rose to keep on "matching" the spec voltage for 77F. In that case (makes sense--brain hurts though) some of my SOCs above could be too low (or is that too high? ) Arggghh!
Anyway it still all comes out that there does not seem to much if any difference between charging AGMs vs Floodeds in real life.
Especially the temperature rise during Absorption is comparable.
I will post this here, but might copy to my AGM adventures thread too.
My 200AH bank was at est 174AH in the 35F/4C ambient as per battery spec sheet on that. Down 80AH by Trimetric before recharge makes that 54% SOC. Used the PowerMax 55 amp ADJ set to 15.2v as equivalent to 14.8v for 77F. Batt V was 12.5 in the zone for 54% by spec sheet.
It did 56 amps constant (56/174 = 32% charging rate) for 25 minutes getting the batts to 14.7v when amps started to taper at about 68% SOC. Batt side temp IR was 8C
At 1 hour- 32 amps, 14.9v, 80% SOC, Batt temp 10C
At 2 hours- 8.5 amps, 15.1v, 86% SOC , Batt temp 12.5C
AT 3 hours- 4.0 amps, 15.1v, 94% SOC, Batt temp 13.5C
EDIT-- The OP's high charging rate didn't seem to make much difference to the SOC when the amps started to taper, because as you remember from my ugly graphs, the curve goes quite vertical at the left so it doesn't do much good to use a way higher charging rate.
BTW plotting that against my old ugly graph with Vectors on Flooded 27s, using the 70a graph (also 32% charging rate) ---
Amps began to taper at 65-68%
80% SOC was reached with amps down to 35amps in the same Absorption time AGM/Flooded ---NO difference.
By the 3 hour mark they are both also just over 90% SOC. NO difference.
EDIT I lowered charger voltage to 13.7 at the 3 hr mark. The Tri showed no amps at all for a while. Yipes! then I realized the battery bank was still higher buy dropping, so no panic. Eventually, the Tri showed charging amps again, but at a lower amps amount. Leaving it there over-night to get to 100% or else I will need a shot of high voltage to get it there. Whatever it needs tomorrow, I can do it.
Obviously it would be better to have more runs at this at more temperate temperatures to be sure, but I am just not seeing the fabled AGM advantage here in fast charging during the Absorption Stage.
I do not have side temps of the Floodeds to compare, but those AGMs sure heat up. 13.5C with 4C ambient is quite a jump.
EDIT-- Forgot to mention that years ago tenbear ( ISTR) was on about whether you should calculate "Full" capacity in AH based on internal battery temp or ambient temp. He thought I should lower the actual charger voltage as actual battery temp rose to keep on "matching" the spec voltage for 77F. In that case (makes sense--brain hurts though) some of my SOCs above could be too low (or is that too high? ) Arggghh!
Anyway it still all comes out that there does not seem to much if any difference between charging AGMs vs Floodeds in real life.
