Fried my brand new BMS, Please Help!

[alexjthayer]

Hi, I recently purchased this https://bmsbattery.com/ebike-battery/322-12s-lifepo4-bms-battery-management-system-battery.html 12S BMS (50-100 amp version)for my custom LiFePO4 pack, I was looking to add a switch to turn on and off the output, and read somewhere that I can short either pole of the thermostatic switch to any of the far right terminals of the MOSFETS to switch offf output the output. This resulted in a huge spark, and while the bms still measures 40-ish-v across the output, I cant draw any current. I now understand that I need to use a low current switch between the Gate and Source of the MOSFETS to switch off output instead. What are the odds of being able repair the BMS, it was about $80 including shipping. There was a clear burning smell right after the short, but there is no physical damage as far as I can see, and the MOSFET "seem" fine, but I am not entirely sure how to test them. Already checked for a fried sense wire from the pack, and tried shorting around the thermostatic switch in case it was blown, no such luck. Not sure what other components to look at replacing. Any help would be much appreciated!

 

[flippy]

The actual control circuit is on the bottom board.

I had the same problem but mine was caused by a slug crawling onto the bottom board and shorting out with the top board.

 

[alexjthayer]

The actual control circuit is on the bottom board.

I had the same problem but mine was caused by a slug crawling onto the bottom board and shorting out with the top board.

That is what I figured... Here is the bottom board, like I said before nothing seems physically damaged (Ignore the traces I scratched out, more on that in a moment)

Here is the Balance line circuitry up close, as far as I can tell the voltage of each line is correct at the input (Bottom) and as it progresses up through the parallel circuits such that the voltages decrease at the same rate... Aka it seems to be fine.
View attachment 1
This is where I think the damage is. This circuitry is related the the thermostatic switch, so I think it got an over voltage or reversed voltage... Just not sure what is fried, and weather it could be hiding under that black glue. To he right below where the white wire meets the board there is a trace I cut, and repaired, this had no effect. The trace towards the top under the white wire I did have some success with. I found that if I connect it, then connect B- to the bored, and then disconnect this trace, there is a good chance of the board working correctly until B- is reconnected at winch point it stops working again. I am worried I may be disabling circuitry that is intended to protect my batteries though.

 

[alexjthayer]

Well, looks like I'll put in an order for another one if no one has any ideas.

 

[flippy]

You are correct. The magic bit is under the epoxy. Impossible to repair or replace.

 

[999zip999]

Somebody needs to start a thread on how to put the smoke back.

 

[999zip999]

Somebody needs to start a thread on how to put the smoke back. I have a pile of stuff.

 

[alexjthayer]

You are correct. The magic bit is under the epoxy. Impossible to repair or replace.

Any idea what there thinking is in covering the important stuff in glue?

 

[flippy]

You are correct. The magic bit is under the epoxy. Impossible to repair or replace.

Any idea what there thinking is in covering the important stuff in glue?

just being dicks, there is nothing special there. it's the same with scraped off IC numbers you get on ebay. they don't want you to know they use fakes.

and please order the next one from http://bestechpower.com/, the quality is a lot better. they do have a minimum order of 2 units but having a spare is no bad thing, and they don't use epoxy.

Somebody needs to start a thread on how to put the smoke back. I have a pile of stuff.

order this:

 

[alexjthayer]

You are correct. The magic bit is under the epoxy. Impossible to repair or replace.

Any idea what there thinking is in covering the important stuff in glue?

just being dicks, there is nothing special there. it's the same with scraped off IC numbers you get on ebay. they don't want you to know they use fakes.

and please order the next one from http://bestechpower.com/, the quality is a lot better. they do have a minimum order of 2 units but having a spare is no bad thing, and they don't use epoxy.

I had considered ordering from them before as they have a much larger range of boards to choose from, but I couldn't find a place anywhere on their website to actual place an order.

 

[flippy]

just email them with the board you want and they will send you a qoute in a few hours usually.

minimum order is 2, bear that in mind.

 

[Ykick]

Bestechpower shipping is expensive and they'll tell you to go pound sand if/when you have any technical difficulties. High-minded "always your fault" business. It's a factory pumping out large orders and doing us a "favor" for small orders, I get it.

But I don't like it and found "good enough" stuff on eBay for similar if not cheaper cost and some PayPal/eBay protection if arrive DOA.

Ironically, the last place to buy a pack BMS is "BMS Battery".

 

[alexjthayer]

Bestechpower shipping is expensive and they'll tell you to go pound sand if/when you have any technical difficulties. High-minded "always your fault" business. It's a factory pumping out large orders and doing us a "favor" for small orders, I get it.

But I don't like it and found "good enough" stuff on eBay for similar if not cheaper cost and some PayPal/eBay protection if arrive DOA.

Ironically, the last place to buy a pack BMS is "BMS Battery".

My first order from BMS Battery took 2 weeks to get to me, when I payed more than enough for 4-7 day shipping, Will not be ordering there again. Also there customer support took their time to reply with very short, meaningless messages.
I ordered my replacement from Green Bike Kit, so far looks good. They have the exact same inventory as BMS Battery... Which is a little strange, but the prices are better for the same product (And shipping is not inflated - Only about 20 bucks), and if they do as they say, they will have it out the door much faster than BMS Battery.


If i happened to dissolve this black epoxy with some acid... Without destroying the board... Would anyone know how to determine the problem part? It looks like the issue is somewhere within about 20 parts that all cost just a couple cents, so I would love to repair this board if possible since it cost me $80.

 

[flippy]

anything that will disolve the epoxy will destroy the board. that is the entire purpose.

 

[amberwolf]

Not necessarily. ATF or brake fluid might do it, depending on the type of epoxy (may have to sit in it a while).

If the epoxy is the same kind as used to make the casings on the transistors and such, then it'll take it off those, too, which would probably destroy them.

 

[amberwolf]

I ordered my replacement from Green Bike Kit, so far looks good. They have the exact same inventory as BMS Battery... Which is a little strange

You might look at this thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=44684&hilit=GBK+BMSbattery

 

[alexjthayer]

Not necessarily. ATF or brake fluid might do it, depending on the type of epoxy (may have to sit in it a while).

If the epoxy is the same kind as used to make the casings on the transistors and such, then it'll take it off those, too, which would probably destroy them.

I might give that a try, but I'm not sure if enough of the circut underneath will be left for me to be able to reverse engineer and repair it.

 

[alexjthayer]

I ordered my replacement from Green Bike Kit, so far looks good. They have the exact same inventory as BMS Battery... Which is a little strange

You might look at this thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=44684&hilit=GBK+BMSbattery

That's bizarre

 

[Ykick]

I ordered my replacement from Green Bike Kit, so far looks good. They have the exact same inventory as BMS Battery... Which is a little strange

You might look at this thread:
https://endless-sphere.com/forums/viewtopic.php?f=3&t=44684&hilit=GBK+BMSbattery

That's bizarre

That's BMSBattery...

I also believe EBL (ebike life) or some BS name is related to these clowns.

 

[alexjthayer]

That's BMSBattery...

I also believe EBL (ebike life) or some BS name is related to these clowns.

If you mean http://www.elifebike.com/, I have never looked at their site before now, but they claim to have a comparable BMS to what i purchased for $27 vs over $50 at Green Bike Kit, or $70 and BMS Battery. Their shipping is also only $17 vs $25ish at Green Bike Kit or an outrageous $50 at BMS Battery. If their legit, there prices are much better. I am hesitant to order anything from them just cuz I have never heard of them once before.