Issue with top balancing

[Grateful.dead]

Hello! First time post a newbie to DIY batteries so take it easy on me ? So recently purchased Eve LF280k for a 12v battery and started balancing a couple days ago. Charging at 3.65v and 9.8-10a with a cheap Amazon power supply. I was using the cheap alligator clamps with 16g wire and wasn’t getting full amps so wired some 12g wire with ring terminals to get some more power. My batteries were at about 3.22-3.24v. I haven’t noticed much change in voltage after almost 30+ hours. All are ranging from 3.34-3.37. I noticed when I tighten the bolt on the studs that has the ring terminals it goes to CC and if I lightly loosen them it goes to CV. Am I doing something wrong here? Thanks in advance been slowly learning and trying to troubleshoot the issue but would love some input! Thanks

 

[Bob B]

Sounds like you have fixed one of the common problems by using more robust leads on the power supply.

Did you adjust the power supply to 3.65V and then connect the power supply .... or did you connect the power supply and then adjust the voltage?
In order to prevent over charging of the cells, you should do it the first way.

When you loosen the lead, you are reducing the current to the cells and that allows the power supply voltage to come up. That would explain the shift you are seeing.

If some of the cells are reading 3.74, you are over charging them. I would disconnect the power supply and re-measure the voltages.... if your bus bar connections are all good, the cell voltages should be the same.

 

[Grateful.dead]

Sounds like you have fixed one of the common problems by using more robust leads on the power supply.

Did you adjust the power supply to 3.65V and then connect the power supply .... or did you connect the power supply and then adjust the voltage?
In order to prevent over charging of the cells, you should do it the first way.

When you loosen the lead, you are reducing the current to the cells and that allows the power supply voltage to come up. That would explain the shift you are seeing.

If some of the cells are reading 3.74, you are over charging them. I would disconnect the power supply and re-measure the voltages.... if your bus bar connections are all good, the cell voltages should be the same.

thanks for the reply! I had a mistype on that question I ment my cells were ranging between 3.34-3.37v after 30+ hours. I’ve been able to get them higher but nothing over 3.4v any other recommendations? Or does it just require a lot of patience? Also is CC or CV recommended for top balance?

 

[MisterSandals]

You need to connect the + to the cell on one end of the parallel pack and the - to the other to charge all the cells evenly.

 

[BentleyJ]

According to the PIC, charging amperage is approx. 10A x 30hrs = 300Ah.

4 cells x 280Ah each = 1,120Ah

1120/300 = 0.268 which means you've only charged 26.8%.
Probably they just are not charged enough yet to see the voltage go up as the current tails off.

 

[E. Cho]

Are you charging with the Grid AC?

IME, with a low amp power supply, it could take many many hours or days to get over the flat part of the charge curve, then the voltage change will rise faster. The previous post calculations show why.

I was charging off grid via my solar charge controller to a battery through the inverter but for 6-8 hours only each day and it was painfully slow progress. Finally, after 3 weeks of doing 2 groups of 4 cells and based on user info from these forums, I gave up and connected all cells in series, connected my JK BMS and commissioned them to into my system and will now let the BMS active balancer and solar charge controller do the work. I have timed this for cloudy days so the charging is slower.

I could not afford a higher amp power supply to speed up the initial top balancing.

 

[Checkthisout]

Your cells have have enormous capacity.

If you didn't charge them with a normal charger first then you are charging them with a teensy little power supply, not just top balancing.

Let's say they need a 3kwh charge.

That's 100 hours (4 days) with a 30 watt power supply.

 

[Bob B]

thanks for the reply! I had a mistype on that question I ment my cells were ranging between 3.34-3.37v after 30+ hours. I’ve been able to get them higher but nothing over 3.4v any other recommendations? Or does it just require a lot of patience? Also is CC or CV recommended for top balance?

Don't worry about CC / CV. Just set the power supply current as high as it will go .... adjust the voltage to where you want them to end up when the current tails off ... Then connect the power supply leads and make sure they are tight ..... be patient. That supply will probably start out in CC mode and as the current tapers off, it will switch over to CV.

Connect them as @MisterSandals suggested.