Have I ruined my LiFePo4 batteries?

[Muaddib1116]

My boat had LiFePo4 batteries installed by the previous owner about a year and half ago. I've had the boat since mid-summer so I have limited experience with them. My boat is on the hard in RI, and because of my stupidity (left the battery switch on), they are now drained down to nothing. My housebank is a 24V bank made of two stacked banks of 4x12V batteries (linked below).

https://szsmartec.en.alibaba.com/pro...171366b93cBbhA

Right now, one bank is around 10.5V and the other is about 11V. Each battery has a built-in bluetooth capable BMS, and only the 11V bank even shows up on my cell-phone app, claiming 2% charge.

For unrelated reasons, my shore power is not working currently, but I can easily run an extension cord from the boat yard's power pedestal.

Have I ruined my batteries?

What type of battery charger should I use to charge them?

Is it ok to charge them in these temperatures (below freezing)?

Any other advice on how to proceed?

Thanks!

[rgleason]

Generally for LFP it is not okay to charge them a low temps. Look at the battery specs to determine what temp you should warm them up to before charging. They should not be used below a certain temperature too.

Operating temp range for Trillian LFP -4F to 140F (Below 32F charging current reduced)
Storage temp range for Trilllian -40f to 140f
(I would warm them up to room temp. then try charging, charging at 32f will be very slow)

I would probably remove them from the boat and get them into a warmer place first. Then when they are warm enough, try charging them, while watching carefully, to see if they are accepting the charge.


The one at 11 amp may be ok, don't know about the 10.5 battery.


Others will have better advice.

[CharlieJ]

Agree with post #2-get them out of the boat and into a space at least 60F and let them warm up for a day or two before applying any charger voltage.

The BMS should have opened the load contactor to save their discharge to external sources. Unfortunately, self discharge continued.

Once they are warmed up, use a power supply set at 12.8VDC (3.2 volts per cell) and set current to <10A to start charging them. This is going to take awhile. Once they accept the low charging rate and they will not accept any charging current at 3.2VPC, start slowly increasing the charging voltage over several days until you reach 3.6VPC or 14.2VDC open circuit. At no time allow the charging current to exceed 20A.

[Midnight Son]

Thank you Charlie.

[Muaddib1116]

Thanks for the advice guys! We've got a snowstorm coming the next couple days, but once it's over, I'll go and pull the batteries.

Is there a power supply you can recommend? All I'm finding when I search that are computer power supplys. Alternatively when I look for battery chargers I see a lot of automatic smart chargers.

[Muaddib1116]

It occurred to me that you meant a lab power supply. Would this one work?

https://www.amazon.com/Kungber-Adjus...dp/B08DJ1FDXV/

[smac999]

The victron batteries won’t even let you charge below +5c. The charging bus will shut off.

So I would use simular numbers for others.

[Muaddib1116]

Yeah, I will take them off the boat and bring them home to warm up before charging.

[MerMike]

I've been using one of these:

Variable Switching DC Power Supply HY3020EX 0-30V 0-20A - Volteq - Reliable Regulated Variable DC Power Supplies

I think I found it on Amazon, but it's no longer there. I've had it over a year and it still works.

[CharlieJ]

@Muaddib1116 #6
That power supply will work nicely as will the more expensive and higher capacity unit referenced by @MerMike #9.

[Rough Magic]

Your batteries are most likely Okay. Good advice above on warm them, then charge them. LFP batteries are fine with discharge to 10v, generally. Your BMS may not allow you to charge below 32F (0C). When in operational temp and voltage, the batts will absorb .2C to .4C quite well. Check with the manufacturer for full specs. With care, these batts will outlast SLA batts many times over. Good luck.

[jlcarreiro]

Where in RI is your boat? I'm on the hard in Portsmouth Island park

[KP44]

Originally Posted by MerMike

I think I found it on Amazon, but it's no longer there. I've had it over a year and it still works.

Any amateur radio (HAM) supply will have regulated power supplies that sound like what you want. Be sure to get adjustable voltage. A switching power supply is cooler and more efficient than a linear power supply.

[hzcruiser]

Originally Posted by CharlieJ

[...]

The BMS should have opened the load contactor to save their discharge to external sources. Unfortunately, self discharge continued.

Once they are warmed up, use a power supply set at 12.8VDC (3.2 volts per cell) and set current to <10A to start charging them. This is going to take awhile. Once they accept the low charging rate and they will not accept any charging current at 3.2VPC, start slowly increasing the charging voltage over several days until you reach 3.6VPC or 14.2VDC open circuit. At no time allow the charging current to exceed 20A.

The link provided by the OP paints a different picture: Cut off voltage is 9.0V, so the BMS kept them on.
Once they're around 70F you should be able to just charge them normally, specs recommends 0.2C and max of 1C, that's 30A and 150A respectively.
As they're sealed you won't be able to check the cell voltage, so scratch that. The BMS should take care of balancing the cells if needed.

In the unlikely event they're damaged I would try and get the receipt from the previous owner, they might still be under warranty. And this would be a warranty case.

[CharlieJ]

@hzcruiser

The link provided by the OP paints a different picture: Cut off voltage is 9.0V, so the BMS kept them on.

As I said: The load contactor opened. This occurred at 9.0VDC, self discharge and powering the BMS continued loading the battery.

Once they're around 70F you should be able to just charge them normally, specs recommends 0.2C and max of 1C, that's 30A and 150A respectively.

IMHO, and based on some pretty extensive LFP experience, this is just too aggressive. Slow and steady may well bring these cells back.

In the unlikely event they're damaged I would try and get the receipt from the previous owner, they might still be under warranty. And this would be a warranty case.

Really? While I certainly sympathize with the OP, no battery company warrants there products against misuse.