Help I accidentally broke my BMS!

[Kagamoosha]

I bought a 48 volt 20 amp 14s Lifepo4 Battery off Ebay and I accidentally scratched the circuit board. I believe the battery has a max discharge rate of 60c and a continuious 40c. Now I am looking to replace the BMS board, but it has to be for a 14s battery. If anyone knows anything about BMS and where I can easily purchase a new one please help.
Thanks!

 

[docnjoj]

Please show a picture. If the traces are scratched, they can be repaired with a jumper. Easy and quick. If it got caught in a wood chipper, well, not so easy to fix.
otherDoc

 

[Kagamoosha]

Here are the images. I accidentally touched the circuit board when drilling a hole in the battery box.

 

[dnmun]

what failed on the BMS after you drilled into it? did you lose HVC or LVC? does not look like the trace was cut but there looks like a capacitor or resistor on the upper left might have been hit and knocked off but cannot tell from that picture.

you can verify continuity of the trace and that surface mount resistor with your ohmeter.

 

[Kagamoosha]

Yeah it is a very small scratch. I'm not sure exactly what it damaged, because it would not power anything on the bike. I peeled off some of the silicone to see what got scratched.

 

[alsmith]

Carefully scrape the green lacquer from either side of the break, just 5 or 10mm because that should solder across such a small break without problems.

 

[dnmun]

yep, he could check continuity across that little trace, doesn't look torn, just dented, and that resistor to the left looks ok so it should still work and if continuity fails on that trace then solder across the tear will fix it.

but i looked at that transistor above to the right and it looks like the drain or collector leg is twisted sideways a little so it deserves careful examination with the loupe and maybe check to see if it is functional. it might have been hit by the drill bit.

it could be replaced if bad but hard to tell what it is and where in the circuit it is so we could guess what to use to replace it with.

 

[alsmith]

Yes, I'd seen the transistor then forgot to mention it. It looks like it may be physically ok, just carefully resolder the the pin- it's clear of everything else so don't bother trying to straighten the pin. Also I'd put the soldring iron down onto the other 2 pins just in case they've cracked loose from the board. Use a low power Iron only- too much heat will destroy the transistor- maybe 12 Watts or so at most.

 

[Kagamoosha]

I just bought a new one from the guy that sold me the battery on ebay. Thanks anyway. If anyone is interested in my old one I'll give it away for free!

 

[dnmun]

why do you wanna give it away if it is still functional? i was under the impression you had hit it with the drill but that it still functioned. if it doesn't then do like Al said and solder that drain leg back onto the pad or the transistor if it is broken and it should work again.

 

[999zip999]

Bubble gum and a little spit. Your better off with a new one. Still like to know if the fix.would work.

 

[Kagamoosha]

Here is the conversation I had with the seller when the BMS arrived. It was different than the one I had previously.

Dear imotorbattery,I received the BMS today, but it is not the same as the one that came with my battery. Including the red and black wires it has 14. My battery has a 15 pin connection. They are not compatible.- jonathanparfait

Dear jonathanparfait,

hi friend

oh my friend, i am sorry for it, it doesn't matter, you can cut off your 15 pin plug, and connect the new 14 pin plug from the red line one by one,

You can ignore the 15 black line, are you clare?



Do yall think this information is accurate or not? I don't want to do anything destrimental to my battery

 

[dnmun]

why did you decide to replace the original one? did it fail? i thought you just had hit it with the drill bit but nothing wrong with it.

 

[999zip999]

He could be right and he could be wrong. I would like the same bms. I would not cut and rematch all sense wires.
Please send the correct bms. O.k.
Plus may be fixed but. I don't like doing it that way ( jump wire ? ) on the bms board.

 

[Kagamoosha]

The old one is damaged. I could charge the battery, but if I tried to ride with the bms attached it would kill the power, so I'm not sure why. So I purchased the one but it has a 14 pin connector instead of 15. Does that mean it is made for a certain number of cells in the battery? I know that when you test the cells in the battery with a multimeter the voltage changes from the red wire to the black wire. It sounds like if I connect the battery in the way the dealer is suggesting to the new BMS that it will be one cell short of its current number of cells. I guess the safest way to connect it would be to use a pin extractor to remove the connection from my battery to the new pin connection.

 

[alsmith]

The old one is damaged. I could charge the battery, but if I tried to ride with the bms attached it would kill the power, so I'm not sure why. So I purchased the one but it has a 14 pin connector instead of 15. Does that mean it is made for a certain number of cells in the battery? I know that when you test the cells in the battery with a multimeter the voltage changes from the red wire to the black wire. It sounds like if I connect the battery in the way the dealer is suggesting to the new BMS that it will be one cell short of its current number of cells. I guess the safest way to connect it would be to use a pin extractor to remove the connection from my battery to the new pin connection.

You can always charge using that old BMS and take power directly from the battery bypassing the BMS- BUT you need to watch your voltage doesn't drop too far to avoid battery damage. This would at the very least get you mobile while the incorrect bms is exchanged.

 

[dnmun]

would help to know if the battery itself is balanced and if you post up a picture where we can count the channels we can tell you if the new BMS will work and how to do it.

 

[Kagamoosha]

I believe the battery is ballanced, but it is sealed in two layers of plastic wrap, so I can't tell for sure. There is one main negative and one main positive. I inlcuded a close up pic of the battery cable and the new BMS connection point.

 

[dnmun]

plug that 15 pin plug into the old BMS and measure the voltage between each adjacent pin on the BMS pcb where the pins are soldered. the black wire is the bottom of cell #1 so measure between it and the next wire, then do that for each successive pair all the way up to #14 and measure while charging. list the cell voltages here and post up a picture of the mosfets on the old BMS so we can see how it works to give you an idea of where to measure.

 

[Kagamoosha]

I figured I would open up the vinyl casing to get a better look. I plan on wrapping it with a nicer fabric anyway. Hope this can help.

 

[dnmun]

it looks like you own a voltmeter because there are probes in the picture so why can't you just measure the voltages on the BMS where the sense wire plugs into the pcb while it is charging?

if you will take the heat sink off the BMS and take pictures we can see how it is built then can tell you how to test it.

 

[Kagamoosha]

Alsmith wrote
"You can always charge using that old BMS and take power directly from the battery bypassing the BMS- BUT you need to watch your voltage doesn't drop too far to avoid battery damage. This would at the very least get you mobile while the incorrect bms is exchanged."

This is what I decided to do. The other BMS kept shutting off, so I hooked the old one back except I won't be drawing power through the BMS, just charging. I am using a Watt Meter similar to Turnigy but when my battery is fully charged the meter doesn't work until it drains some volts. For some reason it is rated for 60 volts, but can't even handle 51 volts. My battery gets to around 58 volts when fully charged. Rather than shelling out $150 for a Cycle Analyst something with a larger display.

http://www.amazon.com/High-Precision-Power-Meter-Analyzer/dp/B00C596UIA/ref=pd_sim_t_3?ie=UTF8&refRID=1TEAHPVX03N1C99QW5DX

 

[alsmith]

Alsmith wrote
"You can always charge using that old BMS and take power directly from the battery bypassing the BMS- BUT you need to watch your voltage doesn't drop too far to avoid battery damage. This would at the very least get you mobile while the incorrect bms is exchanged."

This is what I decided to do. The other BMS kept shutting off, so I hooked the old one back except I won't be drawing power through the BMS, just charging. I am using a Watt Meter similar to Turnigy but when my battery is fully charged the meter doesn't work until it drains some volts. For some reason it is rated for 60 volts, but can't even handle 51 volts. My battery gets to around 58 volts when fully charged. Rather than shelling out $150 for a Cycle Analyst something with a larger display.

http://www.amazon.com/High-Precision-Power-Meter-Analyzer/dp/B00C596UIA/ref=pd_sim_t_3?ie=UTF8&refRID=1TEAHPVX03N1C99QW5DX

OK,. But remember this is a compromise, not really meant as a 'proper' long term solution. I still recommend you do it properly when you can.

 

[friendly1uk]

Alsmith wrote
"You can always charge using that old BMS and take power directly from the battery bypassing the BMS- BUT you need to watch your voltage doesn't drop too far to avoid battery damage. This would at the very least get you mobile while the incorrect bms is exchanged."

This is what I decided to do. The other BMS kept shutting off, so I hooked the old one back except I won't be drawing power through the BMS, just charging. I am using a Watt Meter similar to Turnigy but when my battery is fully charged the meter doesn't work until it drains some volts. For some reason it is rated for 60 volts, but can't even handle 51 volts. My battery gets to around 58 volts when fully charged. Rather than shelling out $150 for a Cycle Analyst something with a larger display.

http://www.amazon.com/High-Precision-Power-Meter-Analyzer/dp/B00C596UIA/ref=pd_sim_t_3?ie=UTF8&refRID=1TEAHPVX03N1C99QW5DX

OK,. But remember this is a compromise, not really meant as a 'proper' long term solution. I still recommend you do it properly when you can.

It is imperative that you don't blindly charge the battery expecting the bms to be balancing and watching for a high voltage condition. You can't expect it to do anything at all. It wouldn't use it personally.
I would rather take it off and recognise that I am bulk charging while another arrives, or somebody sorts out the new one.

A broken bms could be worse than no bms.

Safety first.

 

[999zip999]

It would be good to know the voltage of each cell. You can check at the plug when plugged in to the bms. These is safer becausew you don't want to touch the probes neg. an dpos togethere when touching the hot pins on the board. I put shrink wrap on the probes so it is harder to short or touch pins.
1. 3.65v
2. 3.55v
3. 3.88v ect.



14. xxx volt.
This will telll you the health and balance of your battery,