is this an indication of battery overheating
- Thread starter pellicle
- Start date
Please read my response to your other post, RIGHT NOW.
Is that top circular smudge approximately the same diameter as a fingertip? There is no indicator of scale, but if it is, that is likely an impression of a single cell, and may, or may not, indicate a problem.
Is it just dirt or oil that will just rub off, or is it IN the plastic? If it is, that could be very, very bad.
If it starts to go, things get real serious very quickly. Smother it with something non-flammable, NOT water, and get away from the fumes. They are toxic.
Is that top circular smudge approximately the same diameter as a fingertip? There is no indicator of scale, but if it is, that is likely an impression of a single cell, and may, or may not, indicate a problem.
Is it just dirt or oil that will just rub off, or is it IN the plastic? If it is, that could be very, very bad.
If it starts to go, things get real serious very quickly. Smother it with something non-flammable, NOT water, and get away from the fumes. They are toxic.
Hi
well, no need to yell ... and I don't just sit here refreshing the page so ugency is really out of the question, although I appreciate your concern.
the pack is quiet large, its 13.4 Ah 48v pack (13 series group array of 6 18650 cells in parallel), its about 10cm across
well the cover is back on now, and I'm about to head down to my "day job" 200Km from here in the early AM tomorrow, so it will just have to sit here all week without me. I'll have a better look and address if that smudge is a smudge or not later.
It has had some extended usage today, and I put about 20Km on it (in three stages) with some significant hills. However I didn't use it "full throttle" and used it in one of the mid range power modes where the speed is limited to 20kmh
I will of course leave it unplugged and turned off while I'm gone
Thanks for your input, advice and concern
AngryBob said:
well, no need to yell ... and I don't just sit here refreshing the page so ugency is really out of the question, although I appreciate your concern.
the pack is quiet large, its 13.4 Ah 48v pack (13 series group array of 6 18650 cells in parallel), its about 10cm across
well the cover is back on now, and I'm about to head down to my "day job" 200Km from here in the early AM tomorrow, so it will just have to sit here all week without me. I'll have a better look and address if that smudge is a smudge or not later.
It has had some extended usage today, and I put about 20Km on it (in three stages) with some significant hills. However I didn't use it "full throttle" and used it in one of the mid range power modes where the speed is limited to 20kmh
I will of course leave it unplugged and turned off while I'm gone
Thanks for your input, advice and concern
kdog
10 kW
Usually they're just abrasion marks, not really anything to worry about.... but it's good you're inspecting your pack.
The diameter of a single cell is about the size of a fingertip. Hence the question, designed to determine if that smudge is caused by a single cell, which it certainly does resemble.
A cell that got hot enough to melt or discolor plastic is way too hot.
The time interval between "way too hot" and a blowtorch-like flame which will cascade to the rest of the cells in the pack is usually measured in seconds, sometimes fractions thereof.
Lithium cells that do this are typically at either the high end, or the low end, of the discharge curve, or they are defective.
You almost certainly have one or more of those, right now.
As always, it is your behind, not mine, which is on the line. Do as you see fit.
A cell that got hot enough to melt or discolor plastic is way too hot.
The time interval between "way too hot" and a blowtorch-like flame which will cascade to the rest of the cells in the pack is usually measured in seconds, sometimes fractions thereof.
Lithium cells that do this are typically at either the high end, or the low end, of the discharge curve, or they are defective.
You almost certainly have one or more of those, right now.
As always, it is your behind, not mine, which is on the line. Do as you see fit.
The difference between "fully charged", and something other than, and different from, "fully charged", is a very important distinction.
If somebody tells me to travel to Cleveland, and then later says they really meant Miami, I have very likely headed off in the wrong direction.
Some people will tell me that I should be happy and cheerful in such a situation. I disagree.
Such is life, and right now I need to go to the grocery store in order to beat the blue hairs to the chicken breasts on sale before they are all gone.
A good couple of breasts usually do wonders to restore my happiness and good cheer.
If somebody tells me to travel to Cleveland, and then later says they really meant Miami, I have very likely headed off in the wrong direction.
Some people will tell me that I should be happy and cheerful in such a situation. I disagree.
Such is life, and right now I need to go to the grocery store in order to beat the blue hairs to the chicken breasts on sale before they are all gone.
A good couple of breasts usually do wonders to restore my happiness and good cheer.
Yes, I believe it got hot at some point. If it had been a smudge from the outside rubbing against something, the dis-coloration would be shaped like the bus strips, which sit higher than the cell-tips.
Sometimes I see a pack where the cells are adequate, and they run cool because the bus material is steel. In that situation the pack has voltage sag, and the bus strips act as resistors. The buses are hot, and the cells are cool.
Lets imagine that your bus strips are pure nickel, which is over three times as conductive as steel. If the controller requests more amps than the cells can safely provide, then the buses remain cool and cells get hot. It "looks like" three of your cells are running hotter than the rest.
In a best case scenario with what you have right now, the hottest cell does not go into a death spiral, which may set off the rest of the pack into a fire [fingers crossed]. But every time it gets overheated, it rapidly loses capacity, so that the one paralleled string will have voltage sag in a shorter amount of time. When that one P-string starts sagging because its smaller capacity is used up. it begins dragging down the voltage of the whole pack.
After just a short ride, It's as if you are now running a 13S system with only 12S's worth of cells. The BMS (even the simplest and cheapest BMS's) will think the whole pack is now low and the Low Voltage Cutoff (LVC) will turn the battery off. Do as you wish, but I would proceed with extreme caution.
Sometimes I see a pack where the cells are adequate, and they run cool because the bus material is steel. In that situation the pack has voltage sag, and the bus strips act as resistors. The buses are hot, and the cells are cool.
Lets imagine that your bus strips are pure nickel, which is over three times as conductive as steel. If the controller requests more amps than the cells can safely provide, then the buses remain cool and cells get hot. It "looks like" three of your cells are running hotter than the rest.
In a best case scenario with what you have right now, the hottest cell does not go into a death spiral, which may set off the rest of the pack into a fire [fingers crossed]. But every time it gets overheated, it rapidly loses capacity, so that the one paralleled string will have voltage sag in a shorter amount of time. When that one P-string starts sagging because its smaller capacity is used up. it begins dragging down the voltage of the whole pack.
After just a short ride, It's as if you are now running a 13S system with only 12S's worth of cells. The BMS (even the simplest and cheapest BMS's) will think the whole pack is now low and the Low Voltage Cutoff (LVC) will turn the battery off. Do as you wish, but I would proceed with extreme caution.
999zip999
100 TW
why don't you let us know where the battery came from supplier make model. 18650 Tesla like cells is not enough info
999zip999
100 TW
Sorry a repost with my new cheap phone a Coolpad. Junk.
PS E.S. would not let me delete a repost .
PS E.S. would not let me delete a repost .
spinningmagnets said:
thats what I suspected
understood.
indeed, something looks to be running hot to me. I'm not sure of the orientations of the cells within the pack but wonder if its the cells or the bus ... and I'm expecting that its not nickel, but that would be nice.
how much drama is it to unpack that and repack?
should I alternatively just request a replacemnt from the seller under warranty?
agreed, I'm familiar with this issue in NiMH which ran the off grid radio repeater systems I used to service.
yes, but because I didn't pull the pan off and look until after I'd done another couple of longer rides I can't be sure when that heat emerged. When I first got the scoot the seller mentioned that this model had the "unrestricted speed" option still in the firmware. I had not given that more thought until the first ride when I noticed (on that nearly 1km long uphill) that the battery was sagging (I did not study it carefully as I was dividing my attention between it and the road).
Another thought I had is that because the dual motors can pull a peak of 800W each (but I assume that's at the lower RPM when there is less back EMF) that maybe there was too much load for the battery pack to actually cope with?
I wish I had a way of monitoring the wattage consumption.
so then you think (or suspect) that this system has a BMS sealed within it ... I guess that would be prudent.
that I'm posting here is (to me) a clear indication that I'm indeed proceeding with caution. As mentioned earlier once I had that first "stutter" of power I examined the firmware settings and found that the speed limiter was indeed disabled, so I immediately re-enabled it. I wonder if the "stutter" was a momentary drop in voltage below 40 which may have caused the controller to drop out
Since that first "round my block" trip it has not been run without that speed limiter in place, however I have done an extended run a little up a local mountain range. The grade on that is no more than 4degrees. I have my data on that trip here:
none the less, thanks heaps for your input and if there is any interest I'll report here as I find out things.
