48v 16Ah BMS issue...

[Godfreca]

Greetings Fellow Lifepo4 Enthusiasts,

About a week ago my Lifepo4 battery blew out and after careful analysis, and scraping off some safety plastic, I didn't find any loose connections. The cells all measured out normal as well. Unfortunately, it looks like the BMS, particularly the negative discharge (lower right corner) has been taking a beating.

On the negative charge line the multimeter reads 47.3, on the negative discharge line, 37.4. After poking around a bit more with the multimeter I found that the 10v change happens across the coupling adjacent to the frayed discharge line on the very bottom of the board. Is that normal? I'm no BMS expert.

Any thoughts? Think I need a new BMS? Further suggestions?

There's nothing I hate more than not having my battery!

View attachment BMS.JPG

 

[fechter]

Oh, that's ugly. It looks like it was hit by an arc welder on top of the heat sink.

Can you see the bottom side? It may have blown a trace off the board.

The FET drain lead is usually connected to the tab, and therefore the heat sink if no insulator is used. The drain lead should connect to the negative output wire, the source lead should go to the pack negative. You can test the continuity of the wiring up to the actual FET legs.

If those are intact and the FETs are not blown to pieces, then the next thing would be to measure the gate voltage referenced to the pack negative. This has to be done with cells connected. The gate should have something like 10v or so when it is turned on. If there is no gate drive, they can't turn on.

Unfortunately, the interesting parts are covered in black epoxy stuff. If you're lucky, those might be OK.

 

[Godfreca]

Thank you for your reply fechter...

I took at a look at the bottom and it looks, at least as far as I can tell, in tact. I've included a photograph (apologies for it being out of focus).

I'll get to testing the continuity today, hopefully it will be in tact...

Thanks for your help!

-christopher-

 

[Godfreca]

Greetings all,

This is the second time I've posted on this particularly battery - still haven't been able to make it work.

I've tested each of my individual cells and the wiring into and out of the BMS, they all seem fine. However, on my charge line (running to my e-bike), I get a 39v reading on my multimeter. On the charger line, I get the full 48v.

Any suggestions? Can I rewire to the charge line? (I assume not). Sorry if this seems elementary, I've got the LiFePO4 IQ of a third grader... If you have time to respond, please try to keep it in Noobspeak...

Thanks for your time and attention.

-godfreca-

 

[neptronix]

My best guess: loose wire somewhere.

or bad BMS.

 

[999zip999]

Please let use know what was the problem.

 

[Roy Von Rogers]

Your not explaining yourself well enough to understand your question. Take your voltmeter and tell us when the charger is plugged in, what your battery voltage is, and is it rising while its charging. Not sure what type of battery pack you have, so cant advice what voltage it should have.

What type of battery and BMS?
What does the charger say on its label?
Where did you get it from?

etc etc etc.


Roy

 

[dnmun]

first a picture, several would help. where are charge wires connected and where are the other wires you said had the full voltage? you never mentioned who manufactured the battery.