Top balance but little change after 48hrs

[Galway Bay]

I'm top balancing which as expected takes a long time but theres very little progress after 48hrs, so have I got something wrong?

The voltages at the start were
3.34
3.29
3.29
3.33

and after 48 hours charging they are now (I left them connected for 2hours before removing busbars and taking voltage on each separate cell.
3.34
3.35
3.36
3.36


I can put them back into the Seplos mason and charge them a bit more and then take them out for parallel charging in 4's but I thought the starting voltages were close enough to get there fairly quickly so I'm puzzled

 

[littleharbor2]

Are you not at 3.64 now? Sure looks that way.

 

[Galway Bay]

I didn't think so, its showing 5A still going in so that needs to hit zero.... is that right?

Anyway I just restarted charging and its up to 10A and reducing slowly again

 

[littleharbor2]

Your bench power supply wouldn't read 3.64 if that bank of batteries weren't at that voltage. Turn off the power supply and disconnect the leads and check the voltage. It should read near 3.64 volts Measure the voltage of the whole bank after about 24 hours it should have settled down to about 3.40 volts then break it down and check all individual batteries. They look fine from this perspective. I found out th hard way to not bump the voltage knobs on the supply What does the voltage readout read after you disconnect the batteries?

 

[Galway Bay]

When I turn off the power supply, disconnect leads and take voltage its 3.38.

According to the instructions the top dial for voltage is the set-point, then turn the Amps dial to maximum, the charger then starts charging with the highest amps and this falls as the voltage reaches the set-point -- sorry if thats all very obvious - I don't know if all power supplies operate this way?

 

[MisterSandals]

When I turn off the power supply, disconnect leads and take voltage its 3.38.

The power supply voltage? The main point that has been danced around is that you NEED to set the power supply voltage BEFORE connecting it to the battery.

How big are your cells? 280Ah?

From empty:
280Ah x 4 cells = 1120Ah
1120Ah / 5A = 224h (9.3 days)

 

[houseofancients]

I'm top balancing which as expected takes a long time but theres very little progress after 48hrs, so have I got something wrong?

The voltages at the start were
3.34
3.29
3.29
3.33

and after 48 hours charging they are now (I left them connected for 2hours before removing busbars and taking voltage on each separate cell.
3.34
3.35
3.36
3.36


I can put them back into the Seplos mason and charge them a bit more and then take them out for parallel charging in 4's but I thought the starting voltages were close enough to get there fairly quickly so I'm puzzled

View attachment 194316
View attachment 194317

I'm top balancing which as expected takes a long time but theres very little progress after 48hrs, so have I got something wrong?

The voltages at the start were
3.34
3.29
3.29
3.33

and after 48 hours charging they are now (I left them connected for 2hours before removing busbars and taking voltage on each separate cell.
3.34
3.35
3.36
3.36


I can put them back into the Seplos mason and charge them a bit more and then take them out for parallel charging in 4's but I thought the starting voltages were close enough to get there fairly quickly so I'm puzzled

View attachment 194316
View attachment 194317

I think you might want to charge them in series to about 3.45/3.48 , then top balance, otherwise it could still take a number of days

 

[Galway Bay]

The power supply voltage? The main point that has been danced around is that you NEED to set the power supply voltage BEFORE connecting it to the battery.

How big are your cells? 280Ah?

From empty:
280Ah x 4 cells = 1120Ah
1120Ah / 5A = 224h (9.3 days)

Yes I do that all right, so without anything connected I set the voltage to 3.65, amps to maximum, turn off power supply, connect to battery, then power on the power supply and off it goes.

The cells are 305Ah grade B envision.

The bit I don't understand is that I started charging them on the bench when they were say average 3.31v and I wanted to get to 3.65 so they were 90% there....why is it taking so long to charge the last 10% ?

 

[MisterSandals]

average 3.31v and I wanted to get to 3.65 so they were 90% there....why is it taking so long to charge the last 10% ?

I'll guess 3.31V is 70% SoC.

305Ah x 4 cells x .3 = 366Ah
366Ah / 5A = 73h

 

[houseofancients]

Can be much much lower , Pack 2 is envision 305 cells on charge btw