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Hi – I have a new 48V battery bank with Rolls S6-L16-HC batteries (8 X LC16 batteries in series for 48V system). Gear is Schneider MPPT60 and XW6848-01 (plus AGS and Insight communication gear). For solar gear, I have about 2400W of solar output (maximum charge current gets to 33A (low house load) on solar but much higher when on generator output).
Since the batteries are new I am concerned that there’s a 0.025 to 0.030 difference in SG between some of the cells. Most get charged to 1.275 or 1.280 (maybe even 1.285 sometimes) but some others are down at 1.245 or 1.250. For a new bank, I don’t think there should be that much difference between the cells.
My charge Voltage settings are both Bulk and Absorb: 60V (value in the newer version of the Rolls manual – rev6).
End Absorb is at 8.4 amps and 4 hours but the 4 hours is never reached. I assume the MPPT kicks to float due to the End Absorb current at 8.4 amps.
The system seems to work fine but I don’t like the SG delta in the cells
I have EQ'd about 2 times since owning the batteries but I am reluctant to do any more EQ without getting more advice.
After reading the battery manual for the 100th time, I decided to call Rolls technical support.
I was told that I need to spend longer on Absorb and reduce the Bulk & Absorb voltage to 59.4 (maybe 59.6). The message was that I am hitting the batteries too hard at the 60V (even though that’s in the manual) and the cells would even out over time if I charged at a lower voltage for longer (so lower voltage but longer Absorb time). With the charging voltage at 59.4V that I would need to run absorb for approximately 6 hours.
To do that, I think I will tell the MPPT charger to ignore return amps and just use time = 6 hours (360 minutes). Note: I have never been confident in how the Schneider MPPT handles return (or end) amps anyway but at 60V, many cells were getting to 100% full charge OR even over charged.
I was also told to change the temperature compensation on the Schneider gear to -120mV/degree (not the default for Schneider).
The above changes make sense to me and I wish that I had tried this change sooner (bank is 5 months old).
Today is the first day with these new settings and I will watch the SG and charger states today closely and see how this works.
Any thoughts on this issue and the overall strategy of reduced charging voltage but longer time?
Will that help to bring all the cells up to the same SG?
And any thoughts on how much damage I would have done to the bank?
Thanks in advance.
Riley
Since the batteries are new I am concerned that there’s a 0.025 to 0.030 difference in SG between some of the cells. Most get charged to 1.275 or 1.280 (maybe even 1.285 sometimes) but some others are down at 1.245 or 1.250. For a new bank, I don’t think there should be that much difference between the cells.
My charge Voltage settings are both Bulk and Absorb: 60V (value in the newer version of the Rolls manual – rev6).
End Absorb is at 8.4 amps and 4 hours but the 4 hours is never reached. I assume the MPPT kicks to float due to the End Absorb current at 8.4 amps.
The system seems to work fine but I don’t like the SG delta in the cells
I have EQ'd about 2 times since owning the batteries but I am reluctant to do any more EQ without getting more advice.
After reading the battery manual for the 100th time, I decided to call Rolls technical support.
I was told that I need to spend longer on Absorb and reduce the Bulk & Absorb voltage to 59.4 (maybe 59.6). The message was that I am hitting the batteries too hard at the 60V (even though that’s in the manual) and the cells would even out over time if I charged at a lower voltage for longer (so lower voltage but longer Absorb time). With the charging voltage at 59.4V that I would need to run absorb for approximately 6 hours.
To do that, I think I will tell the MPPT charger to ignore return amps and just use time = 6 hours (360 minutes). Note: I have never been confident in how the Schneider MPPT handles return (or end) amps anyway but at 60V, many cells were getting to 100% full charge OR even over charged.
I was also told to change the temperature compensation on the Schneider gear to -120mV/degree (not the default for Schneider).
The above changes make sense to me and I wish that I had tried this change sooner (bank is 5 months old).
Today is the first day with these new settings and I will watch the SG and charger states today closely and see how this works.
Any thoughts on this issue and the overall strategy of reduced charging voltage but longer time?
Will that help to bring all the cells up to the same SG?
And any thoughts on how much damage I would have done to the bank?
Thanks in advance.
Riley