Too much current/amps while in Absorb charging? Am I cooking?!

[intheheartofit]

Pretty much after January my batteries are fully charged every day. I've been watching my amps lately though and they seem high when my batteries are almost fully charged and I almost never get to float.

I have a Midnite 150 charge controller, probably just around 10 years old. Have it setup to go to float when ending amps hit 6.5, upped it to 10 the other day. Battery bank is 428AH S550 Rolls @48 volts. Have had them for 7 or 8 years now and they're about done, but I'd like to see them through till a good Black Friday sale on some lithiums.

Went down the other day to check the acid and found one cell with plates showing even though I just filled it up a month ago. Other cells were pretty close to full still. Got to think I'm baking my batteries with 27amps when almost fully charged and really the amps should be almost to float. When the batteries are at 60 volts the amps should trail off as there's more resistance to flow going into them, no? Or does the charge controller do something more?

Thoughts, should I be adjusting settings? PV array is around 4kw but faces different directions so never get that much.

 

[outboard1196]

By upping to 10 amps to trigger float your ending your charging earlier and undercharging.
But the cell loosing water tells a bigger problem?
When's the last time it was equalized?

 

[intheheartofit]

By upping to 10 amps to trigger float your ending your charging earlier and undercharging.
But the cell loosing water tells a bigger problem?
When's the last time it was equalized?

I probably equalized for 2 hours about a month ago. The Rolls guy told me to avoid if possible and just fully charge. I did have a battery that had a cell not getting charged and for a month I hooked a 6 volt charger up to it. It's still 0.020 SG low but takes a charge. I do have one battery cell that's at like 1.300, not the one that had the plate showing. Maybe I need to do a longer like 8 hours equalization?

When I look down into the plates there is a lot of "fuzz"/gunk on them.

 

[Sweet Tatorman]

A big jump in the rate of water loss from the electrolyte is pretty common as lead-acid batteries reach the end of the road. Increasing the float trigger current as you did is exactly what I would have done. You may have to increase it further if you don't want to spend so much time watering. At 10A on a 428 Ahr battery you are just a bit over 2% which is not really too high.

 

[littleharbor2]

I'm just curious how much of that current is going to your loads?

 

[intheheartofit]

I'm just curious how much of that current is going to your loads?

The full 25ish amps, the battery monitor was at -1 amps out just before I took the picture so it didn't just jump up 0 like it sometimes does.

My baseload is 1.8 amps and I had nothing extra on at the time. Unless the fridge was on but the battery monitor kit doesn't show loads when there's enough power to offset anyways.

 

[intheheartofit]

A big jump in the rate of water loss from the electrolyte is pretty common as lead-acid batteries reach the end of the road. Increasing the float trigger current as you did is exactly what I would have done. You may have to increase it further if you don't want to spend so much time watering. At 10A on a 428 Ahr battery you are just a bit over 2% which is not really too high.

Good to know, now I'm wondering if it's worth a big equalization to try and restore them. The capacity definitely isn't the issue, yet, just the water loss and not going to float. I am a little concerned about that one cell at 1.300 and could try and hook up a 6 volt load to it.

 

[Sweet Tatorman]

One thing to check is what temperature is being reported to the controller. If the temp sensor has gone bad and is reporting too low of a temp the tempco correction of the controller with cause it to charge at too high of a voltage.

 

[intheheartofit]

One thing to check is what temperature is being reported to the controller. If the temp sensor has gone bad and is reporting too low of a temp the tempco correction of the controller with cause it to charge at too high of a voltage.

I'll check that for sure, also I haven't checked the volts of each battery so I'll do that today as well. I did water them all again yesterday and reading posts here I didn't have them in float for two hours so not sure how long it'll be before the SG is accurate.

 

[Sweet Tatorman]

so not sure how long it'll be before the SG is accurate.

The usual practice would be to equalize to facilitate mixing.