four failed smart bms's

Just wondering if anyone had an idea as to why I have had so many Smart BMS's that have failed usually after a couple of years use. ( 4 on 3 different 13s batteries over about 3 years.Is this usual. I am not aware of shorting or damaging them but though ok spotwelding cells together and wiring to motors etc know little about electronics. I am wondering if it would just be simpler and cheaper to get cheapo bms's for about £10 instead of 3 or 4x that price for the smart ones. I can see the pack voltage anyway on bike display or measure with multimeter. Any views and have others had similar short life spans for their smart BMS's. Any recommended BMS's ?

Where did you buy your old BMS'es?

so did 4 BMS fail within the 3 years on same battery or was it all 4 BMS failed at the two year mark on 3 different batteries?

just trying to figure out what's going on.

for me personally, i have an ebike that has the same BMS for the past two years and it doesn't show any signs of failing. but, i only ride like once or twice a week and on occasions when life gets at me then it might be once every two weeks. so that's not a lot of riding or anything.

maybe would help if we knew what the situation was and a little more detail would be good

The BMS's have been on 3 different batteries used on the 3 family bikes. All 13s. 2 failed yesterday seemingly around the same time. May be a coincidence but I altered the parameters on them the day before via an android phone to give a lower cut off for charging and higher for discharge thinking to prolong the battery. Its odd that both went after fiddling with parameters on phone. Could that be a factor. I didn't try to use them though or check the output voltage via a volt meter until yesterday when both were under voltage. All JBD smart bms's. Have now reset to settings recommended here https://endless-sphere.com/forums/download/file.php?id=225465 BMS still displays on phone perfectly giving individual cell settings , pack voltage etc all good, but only give around 2.5v output from BMS instead of the actual pack voltage of around 52v into BMS. If I disconnect the ribbon it gives 50v output.Haven't checked to see if there are any signs of burn marks on board. If so are they relatively easy to repair?

Bought BMS's fom JBD battery store via aliexpress https://www.aliexpress.com/store/1379203?spm=a2g0s.9042311.0.0.96154c4do55VvZ

They call that bricking your BMS. Don't know what the odds are of two of the same BMS going bad the same day after you changed the settings and it just being a random failure.

You have reset the BMS's. Have you looked thru the settings to make sure they match your battery? Have you checked to make sure you don't have a bad/low cell group. Have you tried to turn off the bms/bypass then charge up your battery close to 100%, don't go over with the BMS bypassed. Then reconnect the BMS then.

My BMS was locked after going from a 72v pack to a 48v. But the same would occur if you mistankingly changed the battery pack parameter. All I had to do to unlock it, was to plug in a charger (I believe it's known as a hard reset) and it let me back in via bluetooth, and I was able to set it up for the new pack.

Good luck!

Sent from my SM-A715F using Tapatalk

I lowered the overvoltage and pack overvoltage parameters whilst the pack was fully charged. Could it be that that could have tripped the overvoltage switches and either damaged the board or somehow switched off the battery. Going to run it without the bms to lower the voltage and then reconnect and see what happens. Its odd that I did the same thing to two batteries at the same time, both fully charged and now both bms's seem to have permanently switched off the battery or at least only allowing 2.5v output.

One of the two bms's seems to working ok now. just clicked on the discharge box on the menu on the front page of the android BT display. It was off. Not sure why.The discharge box on the other bms only comes on when charging and I can't "switch" it on when not charging. Balancing, and BT displays all work perfectly, just restricts output voltage to 2.5V

Maybe try a differnt App? YOu should be able to toggle voltage on an off. In the app. Or reload the app, maybe the original you use is not fully implemented or has corrupted firmwares in the MCU...

I have never seen a problem with my JBD boards...



Are they hunting?

Hunting BMS is certain death for the BMS.

Set the balance precision ( lower.. ) ( numerically higher, allowed differences, in cell, SOC voltages, .... ). Meter the( temperature of) resistor bank. Watch the heat.

robb said:

I lowered the overvoltage and pack overvoltage parameters whilst the pack was fully charged. Could it be that that could have tripped the overvoltage switches and either damaged the board or somehow switched off the battery. Going to run it without the bms to lower the voltage and then reconnect and see what happens. Its odd that I did the same thing to two batteries at the same time, both fully charged and now both bms's seem to have permanently switched off the battery or at least only allowing 2.5v output.

Click to expand...

My guess is that what you did ( lowered the max voltage while the battery was charged beyond that voltage ) caused the BMS to go into drain mode on every cell. This could have created an unusual amount of heat that's not common during normal BMS operations - possibly beyond the thermal design of the BMS itself.

Have you physically inspected the boards yet?

robb said:

One of the two bms's seems to working ok now. just clicked on the discharge box on the menu on the front page of the android BT display. It was off. Not sure why.The discharge box on the other bms only comes on when charging and I can't "switch" it on when not charging. Balancing, and BT displays all work perfectly, just restricts output voltage to 2.5V

Click to expand...

looks like you might have to compare the settings on both and maybe one of them might be glitched. keep us updated and good luck.

Hi all, both BMS's are now functioning correctly ( I think) The problem seemed to be that the switch function in the function setting from menu had got turned on somehow. I turned it off and now both bms's are carging and discharging normally. Thanks for help Have attached screenshot