Why is my LiFePo4 pack charging slowly?

[Freep]

I had an unscheduled full discharge test his morning. Last night we came home from our camping trip and I plugged the camper in, forgetting that I had flipped the AC breakers when I installed the new battery. I left the fridge running on DC. This morning I went to get something out of the camper and noticed a fan was running slowly and I realized I had no power. The BMS kicked in as it should have and I flipped the breakers on and it started charging like a champ. At first it was taking something like 30 amps but I just checked it and it's 68% charged but only charging at about 8 amps. so that's about 6.5 hours of charging. I've got a PD4045 converter charger and the solar has been pumping in electrons too.

Any ideas why it's taking so long to charge?

Is it unreasonable to expect it to be finished by now?

This is a 271ah 4s pack.

 

[DThames]

The normal charge is at first constant current, then once the voltage is at the charge level, the current starts dropping off. What is your battery voltage when it is charging less than 30 amps? if the voltage is something like 14.0 to 14.4 volts you could expect to be in the constant voltage mode with lower current. Not sure where the 68% comes from but I don't trust those numbers that much, but look at the volts and amps.

 

[Freep]

13.6 volts charging at 6.8 amps

Edit: the 68% comes from the BMS app.

 

[grizzzman]

13.6 volts charging at 6.8 amps

Edit: the 68% comes from the BMS app.

Well with enough time 13.6 could overcharge your bank......With that said It takes voltage to push the amps at a higher rate. Turn up the volts

 

[Freep]

Well with enough time 13.6 could overcharge your bank......With that said It takes voltage to push the amps at a higher rate. Turn up the volts

Yeah, it doesn't work that way. It's a PD4045LICSV (45-AMPS) replacement converter charger for a mighty mini. I just have to let it do its thing.

It's not a terrible situation since I know I'd be staying put for 12 hours or so when I'm on shore power and I won't be doing a full recharge. I was just surprised that it slowed down like that. I guess I should write the manufacturer and verify that's how they programmed it.

 

[John Frum]

Yeah, it doesn't work that way. It's a PD4045LICSV (45-AMPS) replacement converter charger for a mighty mini. I just have to let it do its thing.

It's not a terrible situation since I know I'd be staying put for 12 hours or so when I'm on shore power and I won't be doing a full recharge. I was just surprised that it slowed down like that. I guess I should write the manufacturer and verify that's how they programmed it.

It may not be charging your battery quickly but it will help with whatever loads are present.
I doubt it will overcharge your battery either.

Charge voltage experiments with lithium iron phosphate batteries showing how capacity varies with charge voltage and higher cycle live with lower charge voltage

Engineering resources for designing equipment using lithium iron phosphate batteries from PowerStream

www.powerstream.com

 

[grizzzman]

I just Picked up a PowerMax PM-3 55LK converter. You can run it as a 3 stage charger converter... or... Flip a switch and turn a pot to adjust from 13 to 16.5 volts steady. I take that you can not at least turn up your solar?

 

[John Frum]

I just Picked up a PowerMax PM-3 55LK converter. You can run it as a 3 stage charger converter... or... Flip a switch and turn a pot to adjust from 13 to 16.5 volts steady. I take that you can not at least turn up your solar?

I just got the pm3-30-24lk.
I going to be waiting on my batteries a while.
Have you tested the 3 stage charging with a lifepo4 bank?
Does it do sane cc/cv charging with termination to a sane float voltage?
Hope this isn't considered a hijack.

 

[grizzzman]

PD9145ALV 45-AMP
Input Voltage: 105-130 VAC 50/60 Hz 725 Watts
Output Voltage: 14.6 VDC 45 Amps
Dimensions: 8.25” L x 7.25” W x 4.7” H
Weight: 4.5 lbs.


Dang... I hope you didn't trash your battery.

 

[grizzzman]

No, not yet. Mainly due to it dropping boost after 1/2 hour.( Well that's what I have read )

 

[John Frum]

No, not yet. Mainly due to it dropping boost after 1/2 hour.( Well that's what I have read )

With a lifepo4 battery the boost is likely irrelavant.
The internal resistance of the battery is so low that it can't go into boost mode or it would not be current limited.

 

[Freep]

OK according to this it's CC/CV and charges at 14.6 so it's probably designed to charge fast at first and then taper off like it seems to be doing.

I set my BMS to stop when any cell hits 3.5v or the pack hits 14v. I don't really need to push it all the way and I figured that was a pretty safe spot to stop.