BMS broken, damaged cells, or both?

Hey guys,

I have a 60v42ah batterypack. My bike has two 2800w engines and two 40A controllers. All is less then 6 months old, so more or less new.

The batterypack is a chinese 16s13p, I could choose how many Ah the pack had when I bought the bike.

I played around with different controllers a lot, and apparantly put it to the limits of the battery.
Engine started to loose power and I smell burning, plastic smell.
I stopped the engine the moment I smelled something, but I realised with this smell... There will be damage. One way or the other. No smoke though.

I walked home, opened up the battery case, terrible smell.. Hot.

I took out the battery and put it outside to cool down.
After maybe 45min I measured voltage, staight at the xt90 connectors of the pack: 62v. Normal!
Connected it to the engine to see what would happen: It has a external voltmeter, connected to the key ignition. The moment I switch the key I see the voltage going down very fast.. Till 32v. When switch the ignition off-on again, it goes up to 60v again, and then going down again..

The engines have not enough power to function.
No more burning smell, except for the smell still in the pack from before, quite smelly still and not a good sign.
The smell only seems to come from the front of the pack,
Where under the blue wrap, the BMS is situated.

What I did is ordering a new BMS.

The younger version of me would just connect the new BMS when it comes in(This week), and just see what happens..
Now I am a little older, 40+, with kids in my bought house, I just realised it might be better to do some examination, in stead of putting my head in the sand, acting like a cheap dutchman, assuming there is no further damage after that terrible plastic smell, and just connect it..

Could someone tell me.. With this symptoms... Do you supect the BMS?
I have to remove the blue plastic to remove the bms anyhow, should I measure voltage at the big white BMS connector?

I opened her up, please see the pictures. Terrible burning smell. While gently trying to release the bms from the dubble sided tape, a burned mosfet fell out :?

The bms is severly burned, behind the bms they put a piece of protection material. The heat seems to have gone through, you can see blackish stuff on the white batteries:

Yep, looks like the BMS overheated and desoldered itself. You're lucky it did not catch fire.

You need a BMS with a much higher rating. The BMS probably will need cooling as well. Buried inside the pack it can't get much air and the heat has nowhere to go so it overheats.

If the cells were getting hot as well as the BMS, it is a bad sign. Warm is OK but you don't want the cells going much over 40C.

Hi Fechter,

Thanks for your replie.

Yes, I ordered 3 bms's, the BMS from my other bike broke also, both in 1 week. I ordered a 150A with bluetooth, a 120A, and a 100A.
I do all my repairs myselve, except for the battery, I really don't want to.
But in my country we are very very behind.. A pack like mine, nobody knows it, or want to do it. In the whole of Holland, I foumd 2 people who can do battery repairs, other side of the country, charging 250euro just for placing BMS.

So I decide I will try it.

All bms will arrive next friday or saturday. Already little scared..
Before soldered a xt90 connector to the pack, touched each other with the second wire, and the one side I already soldered complete blew of.. Big explosion in my barn :? Promised my wife not to do that again

Go for it. It's not that hard but you do need to be careful with the wires. Tape is your friend. Double check the voltages on the balance wire connector before connecting. When attaching the balance wire connector, try to engage the negative end first. Make the B+ connection last.

Your volt meter is your best friend check before always.
Check voltage check state of charge and balance before installing bms.
1. 3.99v
2. 4.02v
3. 3.85v

13. Xxx volt

Seriously, a "smart" BMS with Bluetooth is your friend.
Anything else is not worth it in my opinion.
YMMV

M

The 120A BMS came in.. It looks quite nice, by coincidence it seems to be the same brand bms, except new one 120A and the old one maybe 60A.
I included pictures with them both next to eachother.. The old one is very very burnt..

So I put my bombsuit on, I prefer not to work direct on the battery, en desoldered the complete old BMS. Already very proud of myselve I overcame this 'being afraid' and did it, but I am still shivering.. I had some bad experiences in the past.

So the BMS is loose, I remember where I take the cables, solder them back in the exact same place.. Only C- is in de front in the old BMS and on the leftside in the new BMS..

The white connectors are also exact the same, so I think I can just plug them back in, after all the other wires are connected?

Please see photo, can I use the complete silver colored strip to choose a spot to solder it in?

Thank you for any advise on my situation..

Bas said:

The white connectors are also exact the same, so I think I can just plug them back in, after all the other wires are connected?

Please see photo, can I use the complete silver colored strip to choose a spot to solder it in?

Thank you for any advise on my situation..

Click to expand...

Looks like you can solder anywhere on the silver strip. It's a little hard to see in the pic, but just make sure those are all the same piece of copper.

When installing a BMS, I recommend the following sequence:
First attach the main B- connection to the cells.
Next plug in the balance wire plugs and try to get the cells closest to B- to make contact first.
Make the B+ connection last.
What you want to avoid is connecting B+ before the lower cells balance wires as this can possibly fry the balancing circuits.

Hi Fechter,

The positive red wires are still soldered on top of the pack, the black ones arr the only ones detached to the BMS.
My bike has 2 controllers, so there were 2 fat black cables, with the xt90 connectors soldered to the BMS. 2 fat black wires going to B- on bms. 2 fat black wires going to P- on bms. And 2 thin black wires to C- on bms, because 2 chargeports.. I guess it doesn't matter which B-black wire goes to which B- hole in the bms?
And.. The red ones are still installed to the pack.. If I first have to connect black, that would mean I have to desolder all the reds from the pack?

OK. You can leave the red wires attached since they don't go to the BMS. Either black wire can attach first. Plug in the negative end balance wires first and you should be good.

Update.. Wanted to place the BMS yesterday, but after first victory of desoldering the old BMS, I decided to first celebrate with a few beers.. Then it was too dark..(Hahaha) I just finished all the nessecary things for today, my freetime has started, so I decided to pre-Tinder the bms board(See pic). A true amateur, I first touched a soldering iron 2 months ago. No wars are going to be won, if it depends on my soldering, I am afraid. Now first a few beers, then put my anti-bomb suit on, that should give me courage enough to touch that damned battery again. Recently I allmost blew my barn, big explosion, eyes and ears did recover after 1 night of sleep.. :/

Thanks for your support, Fechter.
I am ready for it!.. Hahaha

Soldering the bms succeed, without any huge sparks and explosions this time! :wink:
Now the only thing left to be done is connecting the 2 white connectors to the Bms..
Below a photo of the soldering, I used a lot of solder, I trust the connection, it is very very strong

Connecting the white connectors I might do tomorrow, to not spoil my evening with smell of burning wires haha,
Happy weekend!

Progress..

I connected the 2 white connectors to the bms. Checked voltage at the xt90 connectors(to the 2 controllers) 60.8v. The pack is a little more then half full.

I then connected the battery to the bike. The trottle voltmeter tells me 60.8v And it holds!! Before emidiately it whent back from 60.8v to 20v in that same throttle volt meter. Very very promissing. Then I put on my lights, more then 12 in total. Voltage drops to 60.7v and holds that, till I turn out the lights. Then back at 60.8. It now hold its power!!!

Big question now.. Will it charge?

Great news, It now holds its power, and it charges again
Before, the little charge light jumped from green to red, back to green, 1 sec red, etc. Now it stays red and the van keeps on spinning.. Charging.. I stay with it, no part of the battery seems to get hot.
All problems seems to be solved

A BIG thanks to Fechter for giving me the little push I needed. Exactly what I needed.
Thank you, my friend!

Greeting Bas

The question is whatis the state of charge ?. Yes important.
1. 3.87v
2. 4.00v
3. 3.99v



16. Xxx volt
This is the balance of your battery. So how is it.
A bms will help keep a balance battery balance. Don't make the bms to try and balance a fully wonky battery.
Where did you buy the bullet proof bomb suit ?
Good luck.

I haven't completely closed up the batterypack yet, but I was thinking my very expensive charger sees the battery as balanced.. Otherwise it would try to balance them, and I would see the charger light going redggreenredgreenetc..
All bad symptoms I had, are solved.. I prefer because of this not to touch the battery anymore, since I am pretty afraid of it.. The battery sits in a hardened steel box, which is part of the chassis of the bike, sealed with 14 balts.
The battery is still charging, I stay with it till it's charged. Then tomorrow I will take my chances. And testdrive it, and see how it holds.
I don't want anymore direct contact with the battery anymore, for now, but will keep a close eye on how things are going.

And continue my project. Together with the BMS, 2 new 3000w wheel engines arrived, made for speed, with magnectic hight H65. Also 2 new controllers, specially made for this engines, my bike, battery and throttle. The special throttle only works with the 2 new controllers, also arrived.
So now I want to start the nice work, changing the wheels and controllers.. My bike is going to be very very fast, of that I am sure. Also a safe feeling I can't go wrong with choosing power for controllers and wheels.. The specialists did that for me and tuned the whole set. Very curious..

EDIT: PS: The battery is charging for about 2 hours now, and not even slightly warm up, I checked all around the pack. Stays completely cold.

The bms works like these. It charges to one or more cells hit 4.2v then bms shut s off drains the high cell or cells then charger resets charging again tell some cells hit 4.2v then drain the high cells charger turns back on and helps to bring lower cells up. So you can see it can yake a long time before it get to the lowest cell. A lomg time on the charger if just one cell is low. What is your final charger voltage hot off the charger and what is it 5 hours later . If low plug back in and let charger back on and fill it up. Do not run battery to far low now and do not find lvc now. Just try to fully fill up battery for balance. Yes yes after balance is good to only charge to 4.1v for long life but bms will only balance at full charge. Just see if it likes to stay at full charge voltage.
Yes I see you point as there is a lot of stored energy.

Hi,

Yes, I read what you write.. I am starting to doupt now also..

After readimg before what you wrote, you scared me a bit, so I did not charge it fully till the red charging lights on the charger both became green.
Not full 67.6v highly charged to begin with, first see how it would behave..

2 new 3000w engines with magnetic height 60H came in, together with 2 controllers and special throttle..
I finished installing everything half an hour ago, and took it for a short spin!

Complete new very very powerfull wheels with tires for driving trough thick mud. 2 high speed controllers, made special for this wheels, for ultimate speed. With the new 120A BMS, lots of current all of a sudden.

I took it for a 1.8km drive(like you can see in the picture). Many cyclists and traffic, I could only pull the throttle for a couple of hundred meters, a lot of torque, must hold myselve with a lot of power to not be blown of. In about 4 seconds to 60km,then I let go. I have seen enough, that is fast, that is torque, that is the bike just wanting to do 1 thing and that is going fast.

Although no holdback at all, I saw the voltage in the voltmeter(arrow in picture) fall back to about 56v when I did that fast little piece. The moment I let go the throttle, it went back to 63v(Not fully charged, fully charged 67.6v).
The moment I saw that, I did another fast acceleration, same again, fall back, and recover.Not to be noticed in the driving. New BMS feature? :?
I am afraid not. Can't remember for sure if that voltmeter on the steering wheel did that before, bike is pretty new, but I think not..

EDIT:
So I should charge it to full? So it can balance? Ok.. I will take the bike inside in my sight, and take a beer. And keep an eye on the bike and this forum

Putting the charging to the test, put the bike in livingroom next to my wife :lol:
Duo charging it with 2x 5A chargers. Battery is locked in thick hardened steel box with 12 bolds, I am pretty sure when the battery would fully explode, battery would not leave this box, although it would give a nice BOOM sound..

I love you. Yes go ahead and charge and monitor. Well you have a device for you own device . ? . You hand test with thermal nulclur device your hand. Can it light a cigarette ? Ok bad.
Really it should not melt wax or just about.

Both chargers report Full at 66.3v.

But it going down, after 15min already 66.2v, with only the display on. That can't be good

Check voltage of your charger?


Live off disply after recoord ful lcharge

Hi, the charger says 67.2volt full..