Trying to top balance my diy lifepo 24v 310Ahr battery bank. The cells are at about 3.3v as of now. I tried connecting them to a bench power supply in parallel but after a few days the amps are still at about 5.5a. It has been suggested to put 4 cells in series and charge with a regular charger and then finish them off with the power supply as above. I have a PowerMax 100 amp charger. My question is, is it safe to use this charger? The specs on these batteries indicate a continuous charge rate of 50 amps. This seems quite low for a 310ahr battery?
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Charge 310Ahr lifepo at 100amps?
- Thread starter atWar
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Did the current start out higher and has subsequently tailed off to 5.5 amps? Most bench power supplies can give more than 5.5 amps. If the current has tailed off, it sounds like you're already getting close to the knee. What is is the voltage on individual cells?
BentleyJ
Solar Wizard
General rule for recharge current on LiFePO4 chemistry is 0.2C for longest life.
310 x 0.2 = 62 Therefore under normal circumstances the charging current should be 62A or less. For example, if your battery is discharged to 50% capacity it would take approx. 3.1 hours at 50A to fully recharge.
310 x 0.2 = 62 Therefore under normal circumstances the charging current should be 62A or less. For example, if your battery is discharged to 50% capacity it would take approx. 3.1 hours at 50A to fully recharge.
Yes, the current started at about 6.4 amps but it took about 4 days to drop to 5.5. I can't seem to get 10 amps out of this power supply even with it cranked up all the way. When I set the voltage to 3.6 the current dropped to 6.4.Did the current start out higher and has subsequently tailed off to 5.5 amps? Most bench power supplies can give more than 5.5 amps. If the current has tailed off, it sounds like you're already getting close to the knee. What is is the voltage on individual cells?
I should have been clearer. I will be charging the battery with a Growatt ongoing. I just want to use the PowerMax to quickly charge to near the top and then finish off the top balance with the bench supply. Just not sure 100 amps will damage the battery in some way.General rule for recharge current on LiFePO4 chemistry is 0.2C for longest life.
310 x 0.2 = 62 Therefore under normal circumstances the charging current should be 62A or less. For example, if your battery is discharged to 50% capacity it would take approx. 3.1 hours at 50A to fully recharge.
100 amps is fine. I assume charging in series with the BMS connected. Just place in service and watch for cell over volt. Once assembled I would not want to break it all down again for parallel and then build it back for series. Active balancer or manually balancing individual cells as needed is fine and can be completed while in service.
Any chance the bench supply cables can be swapped to #10 wire and ring terminals? This will get the 10 amps expected.
Any chance the bench supply cables can be swapped to #10 wire and ring terminals? This will get the 10 amps expected.
Half of that was probable burnt up as heat in the 24awg leads he used.6.4 amps for four days should be well over 310ah
6.4amps x 24hours x 4days = 614 amp-hours6.4 amps for four days should be well over 310ah
8 cells x 310amp-hours = 2480 amp-hours
If started at 50% the top charge is maybe half done. Would be a lot closer if better wire was used to get 10 amps.
Still have them in parallel. I did switch out the cables for #10 with rings and I am now getting 10 amps but when I set the amps the voltage dropped from my setting of 3.6 to 3.4. The battery is already at 3.4 but the power supply seems to be chugging away.100 amps is fine. I assume charging in series with the BMS connected. Just place in service and watch for cell over volt. Once assembled I would not want to break it all down again for parallel and then build it back for series. Active balancer or manually balancing individual cells as needed is fine and can be completed while in service.
Any chance the bench supply cables can be swapped to #10 wire and ring terminals? This will get the 10 amps expected.
Disconnect, set the voltage to 3.60-3.65, verify with second voltmeter, reconnect. Should get 10 amps and voltage should sag a bit to match the cells. Voltage will rise to the set voltage when the cells are charged. Do not adjust voltage to get more amps while connected. Very easy to take the whole pack over volt.
Bud Martin
Solar Wizard
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That is normal for the power supply Voltage to drop since the power supply is in CC (Constant Current mode). What ever you do, do not adjust the output Voltage after you have the power supply connected to the batteries.Still have them in parallel. I did switch out the cables for #10 with rings and I am now getting 10 amps but when I set the amps the voltage dropped from my setting of 3.6 to 3.4. The battery is already at 3.4 but the power supply seems to be chugging away.
Got it. Thanks for your helpThat is normal for the power supply Voltage to drop since the power supply is in CC (Constant Current mode). What ever you do, do not adjust the output Voltage after you have the power supply connected to the batteries.
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