New LiFePO4s don’t want to take a full charge.

[Bearpaw]

I bulked up my old lead acid 48V battery bank up with a generator to a full charge. My new LiFePO4 48V replacement charges up to 54V (top charging voltage as per mfg. spec.) and quits drawing current from the generator into the batteries. I don’t understand why. Consequently I am unable to fully charge the battery bank. Does anyone have any ideas why this happens? The battery bank is getting more depleted by the hour. Recharging only seems to bring up battery voltage, not Ah.
Generator is a 120/240V capable of both voltage and 120A. MS-4000 Magnum Energy inverter/charger is limited to 60A charge current. Battery manufacture has spec. out the following: System Voltage 48V, Max charging voltage 54V, LBCO@42V, operating voltage 48V. Battery Ah rating is 200Ah. Each battery consists of 16 individual cells. I have 2 batteries in parallel on 2 charge controllers and 2 arrays.

 

[boondox]

I'm going to guess it is somewhere in your inverter settings. I have a Magnum and there are a number of places where you could be running into setting issues. Run through them from top to bottom. If you put a heavy load on while charging does the generator ramp up? Are you using 240 from the generator to charge? You want to for sure.

If you are at least getting up to voltage you are getting enough juice into the batteries to prevent ruining them. By definition if it is bringing up the voltage it is getting current into the batteries.

 

[MisterSandals]

Recharging only seems to bring up battery voltage, not Ah.

This is a curious statement.
How are you measuring or determining amphours?

And as boondox suggests, more info on your charging parameters is needed.
Happen to have a pic of your battery wiring/setup? Maybe someone can spot something, it happens quite a bit.

 

[Bearpaw]

@ MisterSandals SOC displays on each batt. LED. Also, if each battery will display amps coming in as it is accepting the charge.

 

[Bearpaw]

@boondox The batteries are limited to the 54V max charge voltage. Yes, the generator is wired and running @240V. I’ve just this morning lowered the charging current to 30A and so far both units are accepting the charge @ about 13A &16A each respectively for the first time since installation and for several hours. I would just like to understand why it wouldn’t happen before at 60A charge current. The charge mode would discontinue once the batteries reached the desired voltage.

 

[John Frum]

@Bearpaw do you have a shunt based battery monitor?
If not, I suggest you get one.
Battery voltage is not good way to determine soc with lifepo4 batteries.
Also typical lifepo4 batteries are full at 3.65 volts per cell.
Thats 58.4 volts for a 16s battery.
54 volts is 3.375 volts per cell.
Thats a bit low even for float voltage.

 

[Maast]

If you bought a premade battery pack with its own BMS it sounds like the BMS is restricting input - either it's overheating or some other reason, could be one of the individual cells in the pack are going over voltage.

What brand of battery did you buy.

 

[snoobler]

Battery voltage is not good way to determine soc with lifepo4 batteries.
Also typical lifepo4 batteries are full at 3.65 volts per cell.
Thats 58.4 volts for a 16s battery.
54 volts is 3.375 volts per cell.
Thats a bit low even for float voltage.

^this


@Bearpaw,

If you're charging a 16S 48V LFP battery to 54V, you'll never get it "full". Are you 100% certain about the 54V spec?

Link spec?

The behavior described sounds pretty normal if you see a taper of current until it goes to 0 or near 0. If it just instantly drops to 0, then Maast has it with a BMS trigger on a severely imbalanced battery.

 

[Bearpaw]

@smoothJoey & @snoobler These are closed box battery “packs”. They are 16s. I’ve adjusted the charge voltage to 58 VDC and the charge current increased immediately from 17A & 15A to 26A and 30A respectively for each battery pack. Both packs started to charge very rapidly since the increase of value in voltage and subsequent jump in current. Within about 2 hours both were 100% charged as they should be. I still intend to get a shunt based battery monitor wired into the system. I used to have one on the old lead acid batt. pack.

 

[Bearpaw]

To all who answered my post...

Thank you for taking the time to respond and for sharing your knowledge and experience. Ever since I’d been frequenting the forum you guys have made me want to learn more about this stuff every day. You all are an outstanding group of people!