Is it ok that the cells stay at around 3.55 volts most of the time?

[james1]

I have 1600 watts panels and 16s 280ah battery pack .
But I put this system together to handle winter months when I get extremely overcast skies for 4 or 5 days at a time. And I have insignificant draw down at night. So most of the time the panels will supply all the power during the day and the cells stay at 3.55 with charger absorption set at 56.8 and Float at 54.0.

Just wondering if 3.55 volts is not too much

 

[sunshine_eggo]

That's definitely not optimal. Can you adjust the boost/absorption time?

If not, I'd reduce absorption to 55.2 where a long absorption period is needed.

 

[BentleyJ]

54.0V divided by 16 cells is 3.375V per cell. The math doesn't add up. If the cells are really at 3.55V then the system may not be going into Float mode and I would agree with sunshine_eggo regarding lowing the charging voltage.

If bulk battery voltage is in fact dropping to 54.0V then the cell voltage readings are incorrect.

Are those values coming from a meter or the BMS and the inverter?

 

[sunshine_eggo]

I think the issue is that the charger has a very long fixed absorption period. Many use an arbitrary 10X bulk duration and can result in very long absorption periods.

 

[james1]

That's definitely not optimal. Can you adjust the boost/absorption time?

If not, I'd reduce absorption to 55.2 where a long absorption period is needed.

Thanks for your reply. I don't know. I'll check . It's a Victron Smart solar charger 150-35. But maybe I should reduce absorption voltage especially in spring and fall when I really won't use much power.

 

[sunshine_eggo]

Thanks for your reply. I don't know. I'll check . It's a Victron Smart solar charger 150-35. But maybe I should reduce absorption voltage especially in spring and fall when I really won't use much power.

Important to enable the expert settings as that allows you to set the fixed absorption period. You can also specify a tail current of 14A to drop to float.

 

[james1]

54.0V divided by 16 cells is 3.375V per cell. The math doesn't add up. If the cells are really at 3.55V then the system may not be going into Float mode and I would agree with sunshine_eggo regarding lowing the charging voltage.

If bulk battery voltage is in fact dropping to 54.0V then the cell voltage readings are incorrect.

Are those values coming from a meter or the BMS and the inverter?

Well actually I just put it inservice today. It just never had as chance to go to float. But I understand what you say that the volt should drop to 3.375 after prolonged float. I'll check on that. Those values from bms

 

[james1]

Important to enable the expert settings as that allows you to set the fixed absorption period. You can also specify a tail current of 14A to drop to float.

How long fixed absorption in your opinion?

 

[james1]

Important to enable the expert settings as that allows you to set the fixed absorption period. You can also specify a tail current of 14A to drop to float.

I see you mentioned 1 hour float in one of your previous posts

 

[sunshine_eggo]

I see you mentioned 1 hour float in one of your previous posts

2 hours if charging to 3.45V (no tail current)
15-30 minutes if charging to 3.55-3.65V (tail current to 0.05C, 14A in your case)

Personally, if this is a low utilization installation, I'd do the 3.45 charging for two hours, no tail current.

 

[james1]

Thanks for the advice. I'll think I'll make those adjustments to 3.45 for 2 hours no tail current.

 

[james1]

2 hours if charging to 3.45V (no tail current)
15-30 minutes if charging to 3.55-3.65V (tail current to 0.05C, 14A in your case)

Personally, if this is a low utilization installation, I'd do the 3.45 charging for two hours, no tail current.

So absorption at 55.2 with 2 hours fixed.