BMS in LiFePO4 battery - help me please.

[MickinOz]

Hoping there is a resident expert. I have a PowMr 100 AH LiFePO4 12.8V nominal house battery.
I haven't used the camper for a while, and I was vexed to find the battery won't take a charge. Shows 13 volts at the terminals, until I switch the isolator and connect it to the Renogy charge controller. Then measurable volts drop to next to nothing. After trying all the "reactivate the BMS" tricks that the internet has to offer, including the reactivate function in the Renogy Rover P+ controller, I still can't extract usable power.
Won't take any amps, won't give up any amps.
So I applied some "brute force and ignorance" (as a mate of mine used to refer to all methods involving hammers and sharp objects) and opened the case. Very standard looking arrangement inside. No bulging cells, doesn't smell like the magic smoke has escaped, all 4 cells measure the same voltage (3.32), nothing springs out.
So, my feel is the jbd-zpo4s016-t-s V1.2 BMS is cactus. I think it is defunct, an ex parrot (IYKYK) you might say.
Replacement looks straight forward, but it will take a while for a part to arrive. I may not be able to find the exact part number, but something must be available, surely.
I don't want to buy a new battery, having just spent an enormous amount of money on another hobby, if I can repair this one later. I also look like being up for a new laptop, I'm typing this on an old clunker while I wait for the diet soda to evaporate in my "good" laptop. It's looking like it, too, is cactus. So funds are less fluid than usual.
I have an overnight trip planned for the weekend.
I generally use 12 - 15 AH overnight, so I can do without charging the battery.
Is it safe enough to bypass the BMS and come straight off the cells if I'm only going to use 15%, and won't be deep discharging it nor risking overcharging?
Secondly, are there any recommendations on what specs to look for in a replacement BMS?
Hoping someone can help.

 

[Tony Latham]

Dang!

I. Know. Nothing.

But I'll be curious as to the solution.

Tony

 

[Wandering Sagebrush]

Following

 

[Pmullen503]

There are ways to use the battery by bypassing the BMS. But that doesn't help with charging.

Unless you have a special balancing charger and solder it a balance plug, I'd recommend you wait for the BMS

Even with a new BMS, if you install it wrong or accidently short something while you are installing it, bad things can happen.

LiFePO4 batteries are pretty safe, but working with bare cells requires knowledge and care.

You are asking for permission to do something that we don't know if you are technically proficient enough to do safely.

 

[MickinOz]

Noted. The Renogy charger does have a Li mode, but there is no balancing, of course.
In any case, I don't intend to charge anything. I simply want to use a few amp hours for lights and fan on Saturday night.
I guess the real question is whether it is safe to extract those amp hours without the BMS involved.

 

[featherliteCT1]

I think your battery has Bluetooth capabilities. If so, you should be able to open an app to look at individual cell voltages to see if a particular cell is below the low-voltage cut off protection setting. If that is the case, applying appropriate voltage to the battery, with a separate charger, should wake the BMS up.

 

[MickinOz]

I think your battery has Bluetooth capabilities. If so, you should be able to open an app to look at individual cell voltages to see if a particular cell is below the low-voltage cut off protection setting. If that is the case, applying appropriate voltage to the battery, with a separate charger, should wake the BMS up.

No, this one doesn't have Bluetooth, but doesn't matter. I checked the old fashioned way - with a multimeter. All exactly the same. Have applied voltage to the BMS with an old school power supply I built years ago. All the modern stuff needs to "see" the battery, but this one isn't that smart. I even did the "unplug the balance wires and leave for at least 10 minutes" thing, no difference.
Anyway, I gave up and pulled the big mother flooded lead acid battery out of my boat. It's been sitting on a regulated solar panel since they banned snapper fishing 6 years ago. Working fine. Ol' skool - hard to beat. (As long as you remember to top up the water in the electrolyte every couple of months).

 

[Brumasterm01]

Yes, You can bypass the BMS. Just find the main leads to your battery and tap into those either at the BMS or at the battery terminal.

Your individual cell voltage shows that you likely still have at least 80% of the battery capacity left. It was probably put away full and naturally discharged overtime. These batteries do that. Keep an eye on the individual cell voltage and if you see one drop below 3.1 to 3.0V stop if you want to use the cells again. The problem with these cells is that once you drop below 3.2V the voltage will drop quickly and without the low voltage cut-off of the BMS you can ruin your cells by discharging them completely.

The cells sound like they are in good condition. Just a few years ago I would have bought a new BMS and replaced the old one. I stopped building DIY lithium batteries once 100 dropped below $200. Now they are in the $110-120.

If you are DIY type and want to try reusing the cells here is a non-smart BMS that should do the trick.

4s 8s 12s 16s 100a Lifepo4 Non-Smart BMS 12/24/36/48v

These BMS units are affordable and reliable. They don't have communications built in but they function to protect your batteries from over/under charge, over current, temperature, and has passive balancing. Balance leads are included. Of course the first small black wire goes to the packs main...

batteryhookup.com

It's a good company. I used to buy new and used cells from them to build batteries for my radios.

 

[Tony Latham]

here is a non-smart BMS

Sounds like me.

Tony

 

[MickinOz]

AN UPDATE:
Before I retired, I experimented with running old mobile phones through a shredder. The intention was to generate a fine (-ish) crumb that could be added to the sinter feed. The idea was that this would then report to the sintered product that we were feeding to the blast furnace. When combined with shredded torch batteries, old circuit boards, etc., there was a fair bit of lead, copper, zinc, and gold to be had for nearly free, even sometimes with a treatment charge attached.
Anyway, the distinctive smell of punctured phone batteries is hard to forget.
This morning the lithium battery, after 2 days with the lid on, had that smell in spades.
So that's it - very likely a ruptured cell somewhere. The whole thing is going in the recycling.

 

[MickinOz]

Had a change of mind. In the interests of furthering my education I investigated firther. The clear pressure releief vents on the cells are unruptured, and I can find zero signs of overheating or damage, except for one hot spot on the BMS. I decided to buy a cheap BMS from Aliexpress. I fitted it and the battery is now back to life. I still am not sure I trust it, but the mysteries of LiFePO4 are slowly revealing themselves.
I decided to replace it just the same.