top balancing power supply was at .65a then overnight it went up to 3.6a

[thumper70]

Hi everyone, I am building my first lifepo4 battery and solar setup. I'm a former car mechanic and familiar with 12v systems. I read Will's and other articles about top balancing. Got an inexpensive Dr. Meter 10 amp power supply. I have 8 280ah cells, in parallel. Put the power supply at 3.62 (wouldn't dial in to 3.65, just jumped to 3.68). It started feeding the cells at 4.95 amps. Over the course of 7 days the amperage readings slowly fell. Last Sunday it was at 1.85, Monday .92, Tuesday.61, so I figured today when I got up it would be almost to zero. Uh uh. IT was back up to 3.85 amps. I don't understand. Any thoughts? Thanks Barry

 

[Bob B]

The most common mistake when top balancing is fiddling with the voltage setting AFTER connecting the power supply to the battery.
Always adjust the voltage with the power supply disconnected .... then connect it to the battery ... and then leave it alone.

It is also very common for the cheap alligator clips to cause problems with bad connection .... it is a good idea to replace them with ring terminals to get a batter connection.

 

[DJSmiley]

getting only <5A is clearly an indication of wiring issues. You should get 10A without problems.

Assuming your batteries are at 50% SOC, you have to charge 50%x8x280Ah = 1120Ah, which, at a 10A charge rate, takes approx 5 days. With <5A its more likely to take 10 days..

Better upgrade the wires and lugs. (and consider limiting to 8A, some cheap power supplies will fail if you pull full amps for such a long time)

 

[thumper70]

Thanks for the replies. Unfortunately this power supply won't let me adjust the amps. You turn the Amps knobs up to full, then adjust the voltage that you want before you attach the leads. The power supplynthen puts in the amperage based on the volts. Can't adjust the Amps any higher. As time goes on, the amperage slowly drops. Did not know this when I bought it. Guess I'm in for along top balance. Thanks again.

 

[Bob B]

Thanks for the replies. Unfortunately this power supply won't let me adjust the amps. You turn the Amps knobs up to full, then adjust the voltage that you want before you attach the leads. The power supplynthen puts in the amperage based on the volts. Can't adjust the Amps any higher. As time goes on, the amperage slowly drops. Did not know this when I bought it. Guess I'm in for along top balance. Thanks again.

It's normal for the amperage to drop off as the cell voltage rises.
Replace those leads with something a little larger and use ring terminals and you will help the process a little .... you have too much resistance in your wiring with too small of wire and crappy connections with the alligator clips.