BMS chip getting very hot

[costad]

Hi,

I bought an old e-bike with an old S7 BMS installed.
The battery is discharging itself slowly, and found out the marked IC's in the picture are getting very hot.
All the cells are between 3.62 and 3.68, so guess it's not a question of balancing going on.

Any idea what those IC's are for, and what could be causing them to get very hot?

 

[AngryBob]

7S ?
Brand of bike?
Battery chemistry, lead, lifepo4? If lion you have a serious problem.
Age of bike?
BMS marked as 94V?

Define "slowly" using standard time measurement units, as in, seconds or minutes or hours or days or weeks or months or years or decades. "slowly" is completely meaningless and non-informational.

It is Probably not seconds or decades.

 

[costad]

I bought it used, so don't know much about the bike. The battery is marked Protanium. But I guess about 10 years old or so.
It used to be using lipo polymer batteries, but as they can't be bought anymore, li-on 7s4p was added instead.

It's losing about 1V daily

 

[JackFlorey]

Any idea what those IC's are for, and what could be causing them to get very hot?

They are the cell interface IC's. What's causing them to get hot? Latchup. A gate puncture caused by ESD. A stuck balancer. A high resistance short between V+ and gnd under the IC. It could be a lot of things.

 

[AngryBob]

Protanium batteries still available, but ridiculously high prices.

Your battery is mostly shot, likely unfixable BMS, nearly dead, old cells.

Just buy a new battery of similar specs. Didn't see anything about proprietary battery electronics, but it's not my bike, I would do some research but not likely a problem from that time.

If you were thinking about going to 36 or 48 volt, with a new controller, this would be the time to give that some serious consideration, depending on motor specs.

 

[costad]

All the cells are brand new, I was just hoping that it was a common error which caused the IC's to get hot, perhaps a blown mosfet, diode or whatever. Then giving a shot by replacing that or those parts myself. But I am no electronics expert at all

I did add a new S7 BMS, but I found out that the battery indicator electronics is built-in to the old BMS, so I soldered the old one back again.

 

[AngryBob]

Look, if you are going to dribble out vital information in bits and pieces, this will take a lot longer than really necessary and many will lost interest. The new cells in the battery should have been described in your very first post.

You have a BMS that allows for SEVEN cells in SERIES, or 7s, NOT repeat NOT "S7". That sounds like a model number.

Brand-new cells sitting at the low voltage stated while still being drained even lower will be severely damaged within days.

Since the old BMS is doing the damage, you get to decide whether you want the nice info display or ruin a few hundred dollars worth of cells. This should not be a complex decision. But then, you already put it back, after knowing the damage it was doing, so .....

Good luck to you.

 

[costad]

Ouch, no need to stab me, it's not like I am omitting info, it's just that I don't want to write a fat block of bla bla, if it's not essential to my problem, and then risk you guys losing interest in my post.

Like s7 or 7s, Well I guess you can see that in the image, that it's s7?
I even wrote +-1, 2, 3, etc on the picture, so I don't get why...well you know what I mean.

Also, I didn't know that it was of any use, whether or not it is li-on batteries or polymer. Isn't that the same in the end?
If not, I know that now.

I have of course disabled the BMS when I found there's a problem with the warm IC's.

Like I said, the battery indicator is built-in to the BMS, and there's no info display on the bike at all (on/off button), so yes, I would really like to get my BMS working. If not, I would have to buy a new controller, display, etc.

 

[john61ct]

Forgive Bob, he's just angry.

Doesn't mean he's wrong though.

S7 is meaningless, stop using that.

More info is better than less.

Seems to me you need a new BMS. If you want SoC info, as in coulomb counting, some BMS have that.

A CAv3 adds a lot of value, including a very informative display.

I see no reason to change the controller or anything else.

 

[Dui ni shuo de dui]

Can't really help you on the root cause of your issue, if these two chips get hot there is probably a good reason for that but it's hard to guess since there is no visual damage on your picture.
In any case, I'm not sure it is wise to try and fix it, if it got hot due to some defective component or any other reason, the problem might very well happen again after the fix.
My advice would be to simply replace the BMS with a better one. I suggest you to look for the ANT bluetooth BMS, which features a nice screen to show of your battery state of charge as well as many more information (individual cells voltages, temperatures, discharge current, voltage, speed, etc. You can also connect it to your phone and parameter many things, it's not very expensive and it is pretty reliable.

 

[999zip999]

10 years old what motor geared or dd or rear chain job ? 7s is not much power. Maybe you can go to 36 volt if you're going to buy a controller and put money into this bike but first let us know what bike it is.

 

[miro13car]

logically chip the upper one is a comparator.
during balancing stage -
it compares programmed voltages with actual cell voltages ,

 

[AngryBob]

Anybody find the wiring arrangement on this BMS a bit unusual?

 

[serious_sam]

Anybody find the wiring arrangement on this BMS a bit unusual?

Put it this way, if I wasn't told that it's a BMS, I probably would never have guessed it.

I'm curious about what's on the other side. Surely the sparse/random layout on the visible side is a result of things on the other side. At least I hope so, for the sake of the person who designed it.

 

[AngryBob]

The 94v-0 is a UL flammability test rating.

Could find no ebike-related reference for Zeon 1. Did not look very long.

Fuses a bit unique, but the extra set of wires is what has me curious. Thick wires. Two sets of three in identical color order. Each set with it's own negative. Sense wires in standard configuration with individual string colors and one ground. Standard power wires, properly color-coded.

Ten year old stuff. Way before my time. Might be proprietary and unique to the particular motor.

If only there was some way to get some more information on just WTF this thing actually is, that would be interesting but likely just end up another tidbit of useless information. Then again, it could very well relate to what it could be replaced with, if anything. Oh, well.

 

[costad]

I'm curious about what's on the other side. Surely the sparse/random layout on the visible side is a result of things on the other side. At least I hope so, for the sake of the person who designed it.

There's nothing on the other side of the circuit board.

The cells that used to sit in there are called 5099130L A - https://ibb.co/qnYJ3S0

I went to an electronics mechanic, but he wouldn't touch it without schematics, so still haven't found out much yet.

Other than that I have attached a few pictures so you can see how this 10-12 year old battery was built, in case you were interested :lol:

 

[AngryBob]

I guess the cable thickness was an optical illusion.

Two sets of balance wires? Could this be a balance-charging BMS?

I do recall there was something unusual or different about Protanium batteries, but could not say what. Long time ago I looked into them.