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Old 06-14-2020, 06:31 AM   #1
Anthmatic2
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Default Chargery BMS nearly caught fire!

Last night my Chargery BMS nearly caught on fire after beeping after the cell voltage difference alarm went off. Luckily I was standing there and removed the wires and pulled the BMS off the battery pack before it became a bigger problem.

I've been working on assembling my Leaf lithium pack for a while now and it's been partially installed for a few weeks now and seems to have been working great. As of yesterday morning, my setup was:

- Yamaha G16: 36v, stock motor/controller/everything, lifted with big tires
- 10s Nissan leaf modules
- Chargery BMS16T (admittedly, bought "Open/never used" from Ebay
- LV Relay: Panasonic 12v/400a solenoid (Chevy Volt)
- HV: not installed
- 500amp fuse
- 600amp shunt

Yesterday morning, I found that the cart wouldn't run due to a cell difference. Cell #10 was low by ~50mV. I bumped up the cell difference value in the BMS, charged it up to 90% SOC and the cell difference came back withing 10mV, which I assume is ok.

After this, I decided to tackle two things: Wire up my HV relay and install my 12v converter. The HV relay is a T9AP1D52-12 with a diode wired across the coil and interrupts the (+) charger wire. I tested the relay and it seemed to be operating as expected.

I installed the 12v converter (30amp blue converter) by tying into the same +/- lugs that the cart ties into as well as the key switch. I found it odd that the 12 circuit shares a ground with the cart/battery, but that's the way the instructions and other folks have wired... and it did work.

After that was all wrapped up, I took the cart for a spin and it seemed to be running great, lights worked, and the cell voltage difference didn't seem to drift.

Later that night, I took the cart for another ride which also went fine, but after parking (shutting the lights and keys) the BMS started chirping due to a the cell difference alarm. It was now measuring a 100mV cell difference with cell #6 being the low cell. That's also when I noticed the burning smell and started looking for the source. It didn't take long because the BMS main unit started sparking internally. I pulled the balance leads and other wires out and removed the BMS. It was too hot to hold for 15 minutes afterwards.

There were other signs of heat in the other components. When the BMS cooled, I took it apart and 3 resisters of some kind fell out. The board clearly suffered heat damage and it looks like the -1/+1 leads my have been most affected based on scorch marks.

I think I read about someone having a similar problem, but it was related to regen which I'm my cart doesn't have. I've also reached out to Jason from Chargery, but I was hoping some folks here might have some insight on what to look for or what I might be missing that caused this. I'm a little afraid to install a new Chargery and have a meltdown again, or worse.
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Old 06-15-2020, 04:58 AM   #2
BBBHC
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Default Re: Chargery BMS nearly caught fire!

Yikes! Good thing you were there, could have got really expensive!

Any chance you can share pictures of the internals of the BMS and the parts that fell out?
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Old 06-15-2020, 10:44 AM   #3
Anthmatic2
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Default Re: Chargery BMS nearly caught fire!

Ah, pictures might help! I can't upload images here, so I stashed them in this Google Drive folder: https://drive.google.com/drive/folde...ji?usp=sharing

No signs of heat on the balance lead connectors or the cables themselves.

I also pulled the battery pack and checked the voltage on all of the cells:
1-9: 3.9v
10: 3.8v
Total pack: 38.6v

So the 100mV difference that the BMS was reading seems to be accurate.
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Old 06-15-2020, 11:09 AM   #4
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Default Re: Chargery BMS nearly caught fire!

I see from the Chargery web site that they make a BMS16T as well as a BMS16.

The site shows the "16T" will discharge at 600A while the "16" will discharge at 300A. Are you certain (and I'm sure you are....but just asking) that you have the 16T model?
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Old 06-15-2020, 12:24 PM   #5
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Default Re: Chargery BMS nearly caught fire!

Quote:
Originally Posted by DaveTM View Post
I see from the Chargery web site that they make a BMS16T as well as a BMS16.

The site shows the "16T" will discharge at 600A while the "16" will discharge at 300A. Are you certain (and I'm sure you are....but just asking) that you have the 16T model?
I do have the 16T (aka 16 Pro, I guess). I think the other difference is that the regular 16 does not balance cells.

I'm glad you asked though, I double checked just to make sure!
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Old 06-16-2020, 04:43 AM   #6
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Default Re: Chargery BMS nearly caught fire!

One thing I realized is that I don't have any fly back protection on my LV relay. It seems like that has the potential to send a big spike of battery current back to the BMS... although there are no visual signs of that since the wires, connectors, and that portion of the BMS circuit board look ok.

My relay is a Panasonic AEV14012 M05, which I got from Azlithium. I was under the impression that this relay had flyback protection built in, but after reading this datasheet, that might not be the case. It says:

Quote:
For coil surge absorption, please use a zener diode or varistor, etc., so that the clamp voltage reaches 1.5 times or more (at least 18 V for rated 12 V type) the rated operation voltage.If only a diode is connected in parallel with the relay coil, the contact opening velocity will become slow and sufficient cutoff performance cannot be guaranteed. Please avoid such usage.
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Old 06-16-2020, 05:42 AM   #7
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Default Re: Chargery BMS nearly caught fire!

Time to install diode's.
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Old 06-16-2020, 08:22 AM   #8
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Default Re: Chargery BMS nearly caught fire!

A regular diode vs a zenner diode is not an issue with a golf cart setup since those solenoids don't make/brake current.

However, it is important that you have a diode since it looks like the BMS uses SSR (Solid State Relay) outputs and they can be easily damaged by inductive spikes caused by the relay coil.

I also dislike those designs that keep the solenoids powered all the time, unless you are putting your BMS board to sleep when not using the cart, the BMS (and solenoid coil) is getting hot as it keeps the Solenoids engaged.

You can make simple modifications to eliminate this issue, for example, by installing a small 48v relay powered by the key switch You can interrupt the discharge relay output of the BMS when You turn the cart OFF.
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Old 06-16-2020, 02:21 PM   #9
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Default Re: Chargery BMS nearly caught fire!

Ah, that's good to know Sergio. I think the spike from the solenoid closing seems like the most likely reason that this happened. I don't see any other way that the BMS could melt down like that, unless there was something wrong with the BMS itself.

Sergio, in your example, if the if the small relay is placed on the "hot" side of the key switch, wouldn't the relay never close since big relay is open (and cart has no power)?
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Old 06-16-2020, 03:05 PM   #10
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Default Re: Chargery BMS nearly caught fire!

So, it turned into a Dischargery?
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