LFP/LiFePO battery asleep?

When my 48v battery discharged to 36v, none of my chargers would work. I finally found a source for 42v in my Segway scooter charger. That was just enough voltage to 'awaken' my shore charger.

The point is, any known source of 12v, like another battery, should work for you.

shelbyfv wrote:
It's a 12V 100Ah and it has discharged to 8.94V. It will not take a charge. I have tried the trailer onboard charger, connecting to another 12V and finally bought a dedicated Li charger with an "activation" feature. The last was suggested by the battery manufacturer. I don't know how it became so discharged. It was in the trailer and I'd pulled the fuse for the only known parasitic, the LP detector. It has a BT monitor feature that has also failed. Anyway, I'd appreciate any other suggestions for revival.

If under warranty I would utilize that feature.

If a fixed power supply such as an RV converter will not wake it up there may not be much that can be done externally. May have to open the case and charge the cells directly, bypassing the BMS. This is a tedious process and may need special equipment.

Thanks! The other 12V battery(13+V) didn't wake it up nor did the 14+V Li charger. I'm in contact with the mfg as it's still under warranty. Hopefully they'll offer an exchange. I'll update.

shelbyfv wrote:
Thanks! The other 12V battery(13+V) didn't wake it up...

That's odd. Good luck with it.. perhaps the BMS is shot. What brand battery are we talking about?

X2 on the warranty route.

Most good quality companies will honor their warranties.

Sounds like a BMS failure and generally when they fail, getting them to reconnect is a futile attempt at best.

In the future, you will need to do more than removing the fuse for the LP detector, it isn't the only thing that draws power when things are turned off..

Your RV fridge, 12V radio, furnace and even water heater if DSI all have control boards which are run off of 12V.. Those control boards even when the item is turned off all draw some power.. 12V radio uses 12V to keep your radio stations and memory settings even when powered off.

Add in a battery disconnect switch right at the battery terminal, that will 100% isolate the battery from ever single phantom draw of the RV.

It's a Renogy battery and they have been good responding to emails and offering suggestions. We'll see how it goes from now on. I actually have a convenient battery disconnect but I forgot to use it. I pulled the fuse for so many years it became habit. :o Anyway, pretty sure something went wrong with this one. None of my lead acid batteries ever died under these circumstances. Fingers crossed.

Lead acid batteries also do not have a "BMS" built in that can go wrong and GC batteries tend to tolerate things like running it flat very well with perhaps a bit of loss of capacity and life.

Fair chance the actual individual cells inside your Lithium battery are OK but the BMS has either detected a fault in one or more cells or just plain failed to reconnect for charging after being run down.. Either way, requires replacing the entire battery as the final solution if your charger fails to wake the BMS for charging.

shelbyfv wrote:
It's a Renogy battery and they have been good responding to emails and offering suggestions..

Good brand then they should be responsible.

Just one more idea... a few times when I've been remiss in allowing my 48v pack to deplete to unusable, I simply disconnected the negative cable and let it sit for a while. That 'rebooted' the system (I guess) and allowed some life to return. I do not recall the actual voltage when it woke up, but it must have been over 36 volts to allow the charger to function. It may have been around 42 volts, but that's a guess.

Why it dropped to 36v this time is not understood.

Yes. Load disconnect does work on some. After disconnect period go direct to charging.

May charge at very low current until the voltage comes up. The BT app should work if the BMS wakes up.

In addition to the external charger LI batteries have some kind of electronics inside the case that is supposed to protect and balance the cells. (Like equalization but it's done differently) You may have lost a cell and the BMS (Battery Monitoring System) is refusing a charge to protect from "FLAME ON"

Just a guess..

I recently read a post by an expert who takes these batteries. opens them up and often as not finds the BMS has failed (or one cell) he has a source of replacement electronics so he gets basically Free Batteries.

Alas I did not save a link.