Battery mystery?? BMS problem??

[ebike11]

Hi guys
I have a 48V 10Ah bottle battery and after a full charge about 53V. I then went out and bought a Digital Voltage Meter just to monitor the individual cells health.
At first I tested the main battery pos./neg. leads and all read normal at 50+V.
After taking apart the casing, I located the white BMS connector and was touching the meter leads to the connector and now Im reading 17V on the main leads.
There was no burning, weird sounds etc. when using the meter on the connector prongs. However when I was testing the meter leads on the connector prongs, I did notice a faint
blue spark, VERY faint, nothing that looked like damage but maybe so.

Is there any type of reset on the BMS or something? I don't seem to see anything
Also, is the red wire on the end prong, positive or negative and does it matter where you place the meter prongs??

Any advice is greatly appreciated!!! Thanks


http://oi58.tinypic.com/27zhdzc.jpg

http://oi60.tinypic.com/qnmyz9.jpg

 

[ebike11]

I also just checked each cell again and they are all reading fine..4.12V.
Very strange why the reading is only 17V on the main leads.
Fuse is ok. But I bypassed the fuse just to verify it wasnt the problem.
Still reading 17V. Also the battery on and off switch is working fine.
Strange

 

[Tench]

Some BMS's require to be unplugged from the cells to reset, so try pulling the plug and reconnecting it. and be very careful with the probes on terminals that are very close together!

 

[dnmun]

what usually happens is that the current surge when you short out the probes burns out the shunt transistor on that channel and since it is a mosfet it is shorted so the channel will now drain down to zero because of the shorted mosfet.

it may already be low on that channel so the BMS has shut off the output mosfets but that will not prevent the channel from draining to zero.

 

[ebike11]

Some BMS's require to be unplugged from the cells to reset, so try pulling the plug and reconnecting it. and be very careful with the probes on terminals that are very close together!

Hi, do you mean the white connector plug? It doesnt help, I tried many times.
Also I may have accidentally made a mistake with the probes. Yesterday I seen a very faint dim blue spark,
so Im not sure about that.
Is there a way to bypass the bms to test if the bms is the problem?
Thanks

 

[ebike11]

what usually happens is that the current surge when you short out the probes burns out the shunt transistor on that channel and since it is a mosfet it is shorted so the channel will now drain down to zero because of the shorted mosfet.

it may already be low on that channel so the BMS has shut off the output mosfets but that will not prevent the channel from draining to zero.

Thanks for the reply...so is there anything I should do?

 

[dnmun]

check the shunt transistor to see if they are still functional.

 

[ebike11]

check the shunt transistor to see if they are still functional.

Sorry I never tested a bms board before. Could you tell me the circuit number of it in my photos? Also setting on the meter is DCV?
Thanks

 

[dnmun]

in your picture there is a row of little surface mount resistors for the balance shunt and the transistor that gets damaged is directly above them.

if you plug your sense wire cable into the BMS, you can measure the voltage across that shunt resistor to determine if the transistor is turned on.

if it is on and there is voltage across the shunt then that current is the current flowing out of the battery cell.

if the cell voltage is above 3.60V this is normal and if it is conducting when the cell voltage has dropped below the 3.60V level then it is shorted. assuming your BMS uses 3.60V for the balancing voltage.

 

[ebike11]

Ok thx
I see two rows of circuits with the number 201 on them and a third row of circuits above them.
Do I use the meter on the row above the 201 circuits?

 

[ebike11]

Hi
Could someone be as kind as to let me know the exact place/how to test the shunt resistor etc.?
Thanks in advance!!

 

[DAND214]

I also just checked each cell again and they are all reading fine..4.12V.

If all the cells are at 4.12v, why did you take it apart and short it?

Was it since it had low range or didn't work at all?

Dan

 

[ebike11]

I also just checked each cell again and they are all reading fine..4.12V.

If all the cells are at 4.12v, why did you take it apart and short it?

Was it since it had low range or didn't work at all?

Dan

Oh, I just wanted to test the cells in order to perhaps balance them if one or two cells were not equal to the others, but it was my noobish mistake.
When I still test each cell on the BMS connector, they seem to be reading fine, but the end lead connector for the controller only reads 17V

Is it possible and if so, how can I repair a short?

Thanks!