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Then there is the possibility of a single cell developing an internal dead short. That one doesn’t bear even thinking about as I expect it would be catastrophic. The other 2 good cells would discharge massively into the single shorted cell. The energy released would be enormous.
I've seen a video about EV battery construction that shows how the tabs connecting to each cell are carefully dimensioned to act as fuses. Less catastrophic than a shorted cell, though I wonder how the other two would cope afterwards as they'd get more current going through them than all the other cells in the battery.
 

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E-Niro 64kWh '4' since 9/20 (was Prius)
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I've seen a video about EV battery construction that shows how the tabs connecting to each cell are carefully dimensioned to act as fuses. Less catastrophic than a shorted cell, though I wonder how the other two would cope afterwards as they'd get more current going through them than all the other cells in the battery.
That sounds very interesting. Please do you have a link to that vid? I would like to see it and learn more. Thanks. Peter
 

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That sounds very interesting. Please do you have a link to that vid? I would like to see it and learn more. Thanks. Peter
Sorry, I don't have it handy, and it was a few months ago. It was linked from somewhere here in the SpeakEV forum, and was about a company (may have been British, the presenter certainly was) that had worked on electric racing cars, designing all parts from the ground up, and was using the experience they gained there to design a better EV battery. One notable feature was that they packed cylindrical cells tightly side by side and cooled them only from one end, which works because the thermal conduction inside the cell longitudinally is much better than radially. The trick with the connection tabs was to make one thin and one thick, so the thin one was the fuse, but the thick one didn't dissipate so much heat. Another trick was to use aluminium for connections, because it has better conductivity per unit weight than copper (obviously much more CSA required, but still lighter). Their improvements made the batteries easier to manufacture as well as more efficient and reliable.
Someone else may remember it and be able to find the link.
 

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Kia e-Niro MY20 64 kWh - Gravity Blue
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I think it depends what the exact nature of the single cell fault is. There could be several cell failure modes….
Open circuit cell or very low capacity cell. The battery may still function as the cells are arranged in banks of 3 in parallel. So that bank could still function but with say 30% reduced capacity, and voltage would drop more under load etc. The BMS would soon detect this and limit available power or even shut down.

An Increased internal self discharge in a cell would cause that bank of 3 to gradually become lower SOC than the others in between the 100% equalising charges. The other 2 good cells in the bank could gradually be discharged by the single bad cell In the bank.

Then there is the possibility of a single cell developing an internal dead short. That one doesn’t bear even thinking about as I expect it would be catastrophic. The other 2 good cells would discharge massively into the single shorted cell. The energy released would be enormous.

There could certainly be other cell failure modes possible. I find it quite remarkable that with so very many cells put together in a single battery that they seem as reliable as they usually are IMHO. The quality and consistency of manufacturing must be very high indeed. Peter.
True, there may be many failure modes, but I would doubt any of them are transitory. We have read posts where this occurs randomly and disappears after a restart. Cell failures typically won't be resolved by a restart so that's why I'm thinking it's not an issue with the chemical part of the battery. Then again, I have no clue either, it's just some (il)logical thinking.
 

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Sorry, I don't have it handy, and it was a few months ago. It was linked from somewhere here in the SpeakEV forum, and was about a company (may have been British, the presenter certainly was) that had worked on electric racing cars, designing all parts from the ground up, and was using the experience they gained there to design a better EV battery. One notable feature was that they packed cylindrical cells tightly side by side and cooled them only from one end, which works because the thermal conduction inside the cell longitudinally is much better than radially. The trick with the connection tabs was to make one thin and one thick, so the thin one was the fuse, but the thick one didn't dissipate so much heat. Another trick was to use aluminium for connections, because it has better conductivity per unit weight than copper (obviously much more CSA required, but still lighter). Their improvements made the batteries easier to manufacture as well as more efficient and reliable.
Someone else may remember it and be able to find the link.
Yes, it was a talk by Peter Rawlinson of Lucid motors on how they had made improvements to the battery pack. Was very interesting indeed.
 

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E-Niro 64kWh '4' since 9/20 (was Prius)
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True, there may be many failure modes, but I would doubt any of them are transitory. We have read posts where this occurs randomly and disappears after a restart. Cell failures typically won't be resolved by a restart so that's why I'm thinking it's not an issue with the chemical part of the battery. Then again, I have no clue either, it's just some (il)logical thinking.
I hear what you’re saying. When analogue variables are 'on the edge' of being within normal range or in abnormal range then the (digital black or white, no greys) fault states can completely come and go almost randomly. This is why it would be super useful to gather some OBD2 scanner data of all the cell bank voltages and the delta min/max etc. on any cars that seem to have faults like this, before taking it to the black hole, never to be seen again (dealership). I have car scanner app and dongle always with me. If anything like this ever develops first thing I’ll do is plug in the dongle and scan/capture everything. Especially the 98 cell bank voltages. Peter
 

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Thank you! Here's the video:
WELL worth watching, really nicely presented.
Thanks. I will watch it. (Interesting name the guy has too!)
Of course don't forget that our cells are in the flat plastic pouch prismatic style, not the cylindrical metal clad ones.
Peter
 

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Update on my Niro situation: After two weeks at Kia dealer they tell me it's fixed - they drove it 10 miles with no issues. I pick it up and get less than a mile and it starts happening again - the Low Power error with the Turtle. But this is on the freeway in Los Angeles! It happens over and over as I try to nurse the car back to the dealer. At one point I can't accelerate at all and I'm coasting in an exit lane with my hazards on trying to get off the freeway. I get all this on video and bring back to dealer. For what it's worth, here is what it says on the repair receipt in terms of what they say they fixed:

"upon scanning vehicle for dtc's found code plb9600 high voltage battery cell voltage deviation in history. time that it happened triggered warning light to come on. bms system detected a deviation between high voltage battery cells. opened tech line case 14802173 tech line has advised to replace bms and retest. ordered bms. replaced bms and performed soh reset procedure. test drove vehicle 10 miles no warning lights came on. vehicle operating normally"

this make sense to anyone?
 

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Yes, either the wiring loom in your battery is faulty, a link between some cells is faulty, or one or more cells is faulty. Unfortunately I think you’re in for a long wait until you get your car back with a new battery .
 

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Update on my Niro situation: After two weeks at Kia dealer they tell me it's fixed - they drove it 10 miles with no issues. I pick it up and get less than a mile and it starts happening again - the Low Power error with the Turtle. But this is on the freeway in Los Angeles! It happens over and over as I try to nurse the car back to the dealer. At one point I can't accelerate at all and I'm coasting in an exit lane with my hazards on trying to get off the freeway. I get all this on video and bring back to dealer. For what it's worth, here is what it says on the repair receipt in terms of what they say they fixed:

"upon scanning vehicle for dtc's found code plb9600 high voltage battery cell voltage deviation in history. time that it happened triggered warning light to come on. bms system detected a deviation between high voltage battery cells. opened tech line case 14802173 tech line has advised to replace bms and retest. ordered bms. replaced bms and performed soh reset procedure. test drove vehicle 10 miles no warning lights came on. vehicle operating normally"

this make sense to anyone?
Thanks for the detailed update. I find it bemusing to see that the BMS DTCs very clearly reported that there is some battery cell deviation. So instead of believing the BMS that the battery is bad and replacing the battery, they assumed that the BMS itself was bad! Huh? So they apparently don’t trust/believe the cars own built in diagnostics system.

I wonder if they chose to replace the BMS firstly as it’s smaller/easier/cheaper to replace and perhaps they had one in stock but no actual replacement battery in stock? It seems to me the battery was by far the most likely culprit and should have been the first thing to replace. To pass the car back with the same original potentially dangerous fault remaining is very poor IMO. I wonder if anyone thought to interrogate and view the individual cell voltages list before passing the car back? I bet the fault was obvious. Peter.
 

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Update: Finally got an update yesterday...Kia is going to replace the "high voltage battery pack". I don't know if that means the entire set of batteries or just a special "high voltage" subset, but in any case we'll see if it helps.
 

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Update: Finally got an update yesterday...Kia is going to replace the "high voltage battery pack". I don't know if that means the entire set of batteries or just a special "high voltage" subset, but in any case we'll see if it helps.
That'll be a complete main battery replacement then...

Did they give you a time estimate?
 

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I inquired (via text to the service advisor) as to how long it would take but so far have not recevied a response. I'm guessing (hoping) a couple weeks max.
 

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I inquired (via text to the service advisor) as to how long it would take but so far have not recevied a response. I'm guessing (hoping) a couple weeks max.
I suspect you are going to be disappointed unfortunately.

If you check other similar reports it usually takes more like a couple of months to get the replacement pack fitted and the car returned to you...

Hopefully you may be lucky and perhaps they are finally starting to keep spare packs in the UK, but so far it feels like they are ordering them in from Korea one by one...
 

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I have a feeling that it will turn into a bigger issue. There may be a wider recall for battery replacement of a large number or cars.
Do they use one kind of battery or different?
Could it be one lot of battery only?
 

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I have a feeling that it will turn into a bigger issue. There may be a wider recall for battery replacement of a large number or cars.
Do they use one kind of battery or different?
Could it be one lot of battery only?
The Hyundai Kona battery replacement recall comes to mind...

Even if it does become a recall issue for Kia, it could take a very long time to complete.
 

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I suspect you are going to be disappointed unfortunately.

If you check other similar reports it usually takes more like a couple of months to get the replacement pack fitted and the car returned to you...

Hopefully you may be lucky and perhaps they are finally starting to keep spare packs in the UK, but so far it feels like they are ordering them in from Korea one by one...
But @Tom P is in the US, not UK. So maybe they are better equipped with spares over there? Peter
 
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