New LiFePo4 Not Taking Charge

[Quadrille in JB]

I just purchased a Scremower 100 AH 12v LiFePo4 battery from Amazon.
When I received it the voltage was 13.2 VDC. I attached the little 10A charger that they supplied for ~1 hour but the voltage never changed. I disconnected the charger when it got too hot to touch.
I have an 840AH AGM bank on my boat with 2 Sunpower 360W PV panels which work great, and they accept a charge quickly.
This is my first foray into LiFePo4 and I plan on using it to run a ceiling fan in a small remote barn using a Solaria 370W PV panel (which arrived today) with a Victron 100/30 controller. I use 2 of these on my boat and they work great.
I connected the battery to a Xantrex 1KW inverter and over a period of about 1 hour with a 12.5 A load the battery discharged only 0.1 v. I then removed the load and connected a quality 20A marine smart charger for 1.5 hours and the voltage only went up ~.2VDC and the charger got pretty warm.
Am I being overcautious? My gut feeling tells me that the battery should accept a charge much faster.
Tomorrow I will connect it to the PV panel and controller and see what happens. Any thoughts will be greatly appreciated.
Thanks in advance for your remarks.
Bill in JB

[ThereAndBack]

LiFePo4 batteries have extremely low internal resistance and they have very flat charging curves. That means that the charger may have been putting in a lot of amps even if the voltage is not changing much. You need to measure what the amps in and out are before you attempt to determine SOC based on very small voltage changes.

[Quadrille in JB]

Thanks for the quick answer. My DC clamp on ammeter is in the boat so I didn’t measure the current. Ill pick it up in the morning and measure the current in and update the forum with an answer.

[wholybee]

The fact that the chargers are getting warm sounds like they are outputting current. Probably at or near their max capacity.

LFP will stay at nearly the same voltage until it is nearly charged, then it will rise very quickly. It probably shipped about 50% charged, so you would have several hours of charging until you see a significant rise in voltage.

Certainly check with a meter, and it would be a good idea to do a capacity test also. You can discharge the battery until 10.5V without damaging it, unlike AGM where you should only use 50%.

There isn't anything you said that suggests a problem.

[Wood]

3.2 volts could as low as 20% SOC. A 10 amp charger will take quite a while for voltage to rise. It will increase gradually until around 3.45v when you hit the shoulder and voltage will rise more rapidly.

[MartinR]

Yes, there seems to be no problem. It is just the way LiFePo4 works. In contrast to Lead Acid, Lithium does not like to be at 100% charge for a longer time. So, do not overcharge.

[Quadrille in JB]

Thanks for all of the helpful comments.
I left the 20A charger on for several hours and the voltage rose to 14.1. As noted above, these batteries take a while for the voltage to rise. I’ll connect it to my PV panel tomorrow and see what it does. I think I was just being paranoid.
Attached is a photo of my setup for the remote garage, minus the PV input.

[MartinR]

Originally Posted by Quadrille in JB

Thanks for all of the helpful comments.
I left the 20A charger on for several hours and the voltage rose to 14.1. As noted above, these batteries take a while for the voltage to rise. I’ll connect it to my PV panel tomorrow and see what it does. I think I was just being paranoid.
Attached is a photo of my setup for the remote garage, minus the PV input.

Yes,it works.

If you use only one panel, there is no need for fusing between the solar panels and the controller. The panels have a maximum short circuit current. Different story if several panels are used, though. I would get rid of the circuit breakers, they look the chinese type, notoriously unreliable.

[Quadrille in JB]

I'm basically using the breakers as handy disconnects from the panel and batteries. It makes it a lot easier and safer when working on things.

[Quadrille in JB]

I connected everything up with the PV panel sitting on sawhorses and all worked great. The panel and Victron MPPT controller brought the LiFePo4 battery through bulk, absorption, and float stages just fine.
Now I'll have to wait for the remote garage to be erected before I can do the final install.
Thanks for all of the good advice.
Bill in JB

[UFO]

I set my absorption voltage at 13.8V (approx 90%) and at Zero minutes and my float at 13.3V. They do not like to sit in absorption mode as it still charges them and can cause issues of over charging.

[Quadrille in JB]

Thanks, I'll monitor the charge voltage carefully when I install the system.
Bill in JB