BMS maybe died?

[larrylwill]

Yesterday I went to my MH to check out everything prior to a trip. Everything had been working for a while. I have a 4s Lipo4 battery and 150a smart bms, charged through a 280A alternator and Renology 60A DC2DC.
The MH had been sitting for a couple months plugged in with a charger on the battery, set to come on if the battery got low.

I cranked up the air condition on battery and it started and a couple seconds later everything died. I found that my AC switch had a loose wire from the Inverter, which I fixed and the inverter is ok and the battery is OK and the Air works ok also on AC but not DC through the inverter.
I then nocited the C- on my BMS is read around 1v. I unwired it and checked all connections but I can't get it to turn on. There is no protection activated. Although the program says charge on discharge off. The only other thing unusual is the total pack voltage has about 180mv between cells. The first 2 are high compaired to the other 2.

I am about to declair the BMS defective. I checked all the fets and all check good. The MH will power up on the battery without the BMS. The cell wiring to the BMS is good and the bluetooth works but does not show any current out of the battery but does show current in if I turn on the charger connected to the C- terminal. Yesterday for a while it showed current in from the charger.

Where do I go from here?

[Ken Allan]

Are you sure the battery is actually charged? Does BMS tell you the individual cell voltage?

Do you have a circuit breaker or fuse on inverter?

Cmos is ON, Dmos is OFF = sounds like low battery.

Maybe try a different charger and see what happens. Or try to charge via DC2DC.

[larrylwill]

Originally Posted by Ken Allan

Are you sure the battery is actually charged? Does BMS tell you the individual cell voltage?

Do you have a circuit breaker or fuse on inverter?

Cmos is ON, Dmos is OFF

Maybe try a different charger and see what happens. Or try to charge via DC2DC.

Batery is fine, Reads 13.7v. It charges without problems.
Yes the cells are displayed in the softwear and are accurate. Inverter works and is now not connected but runs the AC through the inverter without the BMS. I only connected the RV circuits.

[Ken Allan]

With my limited experience it does sound like power is not getting thru the BMS. I am mostly familiar with SOK battery. I have seen cases where folks seem to have a similar problem. With bluetooth models, SOK has some options to reset the BMS via BT.

Is your BMS outside of battery or built inside the case? What brand battery?

I would suggest you try to contact the manufacturer of battery or BMS and ask if there is a way to reset BMS.

Sorry I can't offer better help.

[larrylwill]

Battery is homebuilt from Eve cells. The BMS is stand alone. I can and did reset the BT module from the softwear.

[larrylwill]

In case anyone is interested, I found the problem. With my BMS you must attach the B- to the battery before you connect the C-. I built up a 81650 pack to play around and I found the solution.