Charging Troubles with LiFePO4 BYD modules I got from Battery Hookup

[lonewolf754]

I have two of these BYD modules and I'm trying to get them to a charge of 3.5v per cell. One of the modules will reach 3.325v per cell with 17-24mv difference in their voltages. The other module will only get to 3.240v per cell with a difference of 7-10mv.

I check the cell voltages and the total voltage of the module every 10 minutes during charging. The voltages will rise quickly at first and will gradually slow to a stop.

The cell voltages on both modules arrived at my home at 2.7-2.9v.

Here is the ending results from my last charge attempt on my worst module. It's beginning voltage was 24.0v. I checked every 10 minutes.

25.83
25.89
25.93
25.95
25.97
25.97
25.97 -The amperage output on the Korad began slowly rising here, that's why I stopped.

The other module behaves in the same manner. The voltage stops rising.

I stop charging because I'm afraid something "bad" will happen, as I charge these in my home. If both modules stopped progressing at about the same voltages I'd probably think this is normal and I just need to keep charging.


Here is what I use to charge these BYD modules as I haven't finished with my solar panel installation.

1. Korad 30v 5a variable power supply.
2. DROK numerical control regulator DC 8-60v to 10v-120v 15A Boost Converter.

* I set the DROK to 4A CC output and the charging voltage of 28v which is 3.5v per cell.
* I set the Korad to .10v below the actual voltage of the module and it charges in CV mode. I raise
the voltage .10v whenever the module's voltage rises by the same .10v.

I monitor the module using a BattGo BG-8S.

No BMS yet. Plan to get a couple if these modules are found to be good.

*Is it normal for these BYD modules to stop rising in voltage?
*Any suggestions?
*What am I doing wrong?

Any help and suggestions is appreciated. I am new at this.

 

[JJthegreat]

These packs are heavily used and will never stay in balance so dont worry too much. Balance charge it a few times and hope for the best. You will see lots of cell deviation on discharge, this is the reason why they were rotated out of service from that solar farm. Hopefully you will see higher than 3kw of discharge.

 

[lonewolf754]

These packs are heavily used and will never stay in balance so dont worry too much. Balance charge it a few times and hope for the best. You will see lots of cell deviation on discharge, this is the reason why they were rotated out of service from that solar farm. Hopefully you will see higher than 3kw of discharge.

Thank you for the info.

I've been reading everything about these modules that I can find on this forum. Also watching Youtube videos about them and how others are using them.

On charging and discharging, they stay within 20-50mv difference in the cells. But I haven't been pushing them much. Somewhere at 70-100 watts discharging as read by my "Kill A Watt" meter. I don't know how much is actually coming out of the battery.

The major concern I have is that the charging voltage stops rising and just stays there. And it's way below where it should be.

Even though these are old and abused, shouldn't the voltage still get to 3.65v per cell?

Nordkyn Design says that LifePo4 does have memory effect, and he is extremely detailed in his writings about this, I don't know, but I'm trying to get as much info on LifePo4 as I can.

Is this "memory effect"?

When charging I'm getting up to 25.98v on one module, and 26.6v on the other, then it stops. After 30 min. and still not going up, I quit charging.

Should I continue to let it charge?

 

[JJthegreat]

Thats up to you. Since you have no BMS, nothing is shutting off the charging. As long as you dontt let one cell go over 3.7, its all good. The memory effect is actually permanent damage from over and under charging, it results in capacity loss.
Id check the power supply to make sure you have a voltage limit of 29.2v set and actually see if it outputs that when checking with a volt meter, the pack should charge higher than 26.6v.