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It's a long process but yes absolutely. I know that there are new DTCs, so it's possible there are new PIDs. I just hope they don't nuke any old ones.
It would be cool to learn what the new DTCs are.
 

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What have they done to detect bad cell groups now, that they weren't already doing in May/June of 2018. They can't improve temperature monitoring.
It depends a bit how much memory space the BMS might have to store logs, but assuming sufficient memory, if I were GM I'd have the BMS just log a bunch of data related to all battery parameters and send it in to GM. In other words, battery SOC, load, voltage everywhere, etc., when being driven, charged, etc. The goal is to collect everything about the dynamic behavior of the battery. In fact, I'd expect GM to have done this long ago. Also, perhaps have some of their own Bolts with added instrumentation, and some with deliberately faulty packs.

You then crunch that data and get a picture of what normal behavior looks like, and thereby detect abnormal behavior. Google machine learning, anomaly detection, data mining etc.

From this process, you may be able to develop some simple rules “If load is 60 kW and a cell's voltage sags x% more than the average, it's weak” and those rules can the be codified for the BMS.
 

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It depends a bit how much memory space the BMS might have to store logs, but assuming sufficient memory, if I were GM I'd have the BMS just log a bunch of data related to all battery parameters and send it in to GM. In other words, battery SOC, load, voltage everywhere, etc., when being driven, charged, etc. The goal is to collect everything about the dynamic behavior of the battery. In fact, I'd expect GM to have done this long ago. Also, perhaps have some of their own Bolts with added instrumentation, and some with deliberately faulty packs.

You then crunch that data and get a picture of what normal behavior looks like, and thereby detect abnormal behavior. Google machine learning, anomaly detection, data mining etc.

From this process, you may be able to develop some simple rules “If load is 60 kW and a cell's voltage sags x% more than the average, it's weak” and those rules can the be codified for the BMS.
Memory space... oh, no, are we going to have worn out memory chip issue like Tesla after the update? Sigh...
 
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Memory space... oh, no, are we going to have worn out memory chip issue like Tesla after the update? Sigh...
I think it's likely been designed in from the beginning. Just look at the data the “Smart Driver” system has about where you drove, where your braking was harsh, etc. This car is constantly phoning home with data, and you can bet GM is really interested in what is happening in the field with their first real EV (this millennium).

It wouldn't surprise me if they've now turned up the dial for even more data, or to find I'm wrong and they have some telematics data resource and are squandering it just thinking how to sell it to advertisers. But my suspicion is that they already know a ton about what's going on in their Bolt fleet and its batteries.
 

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Can you send me any logs of this? Because that's exactly what I have looked for, and never seen. I have monitored before and after charging for long periods of time, and never seen only one cell change.
I'll try to capture something. I'm almost never in the car until after it's already completely done charging. I'd love to be able to drop the pack out and actually monitor everything through a full charge cycle, but there's no way I'm actually putting that much effort into it.
 

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Discussion Starter · #187 ·
As far as I'm aware there aren't any ODB PIDs that indicate balancing is active and what cells are being drained. There is no way you will see it becoming active by trying to monitor the voltage change because the cell voltage doesn't sag enough. If your pack is well balanced to begin with it'll be basically impossible to observe this. At the very end of a charge cycle I've observed all of the cells slowly reaching the maximum charge point. Occasionally one will display higher for a short period but then come back down as it's balanced out.

The biggest thing is that the balancing system wasn't designed to accommodate major differences in cell capacity. There is no reason to need to be able to if your cells are all matched at production and there aren't defects.
Can you send me logs of that? Because that's exactly what I have looked for, and never seen.

I know that I Can't see it when it's happening, but I should be able to see the result. I have continuously monitored for varying lengths of time, and I never see the higher cells coming back down. I have a 0.025V maximum spread, and it doesn't matter how long it sits, they stay exactly the same.

So it's possible that, with my software, my pack simply never needs to balance. Or, it's balancing at different times than I'm expecting. It's curious that many 2017s have about the same 0.025V maximum spread, which seems to be too coincidental to not be balanced. But like I said, I have never seen one high cell coming down while the battery is idle.
 

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Discussion Starter · #188 ·
I think it's likely been designed in from the beginning. Just look at the data the “Smart Driver” system has about where you drove, where your braking was harsh, etc. This car is constantly phoning home with data, and you can bet GM is really interested in what is happening in the field with their first real EV (this millennium).

It wouldn't surprise me if they've now turned up the dial for even more data, or to find I'm wrong and they have some telematics data resource and are squandering it just thinking how to sell it to advertisers. But my suspicion is that they already know a ton about what's going on in their Bolt fleet and its batteries.
So interestingly I was able to directly ask GM about this. They said that the initial temp fix was ONLY to limit charge - no additional data collection. It strongly sounded like they have very limited phone-home capability, and they were not relying on that for the final fix. I was quite surprised.
 

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Discussion Starter · #189 ·
I'll try to capture something. I'm almost never in the car until after it's already completely done charging. I'd love to be able to drop the pack out and actually monitor everything through a full charge cycle, but there's no way I'm actually putting that much effort into it.
Do you have an old phone that you can just leave in there while charging and after it completes?
 

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So interestingly I was able to directly ask GM about this. They said that the initial temp fix was ONLY to limit charge - no additional data collection.
I think it's a bit of a leap to read into that anything beyond what it is. It may well have been that they did this in order to get the initial fix out quickly without having to go through a more protracted qualification that additional logging and reporting may have required.
 

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Though LiFePo cells are considerably heavier.

The sad fact is that GM investigated using LiFePO4 cells for the Gen1 Volt battery but then went with li-Ion instead. All their subsequent batteries have all been Li-Ion, not the much safer LiFePO4 chemistries. If they had gone with LiFePO4 from the start, quite possibly none of these fires would have happened.
 

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And bulkier. The standard range Model 3 in China, and now Europe, is LiFePO. It is the same size and weight as the long range battery, but only two thirds the capacity.
Well, then LFP was the right solution for PHEV that experience more cycles plus has a gasoline engine to take over when the battery runs out.
 

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Well, then LFP was the right solution for PHEV that experience more cycles plus has a gasoline engine to take over when the battery runs out.
It was also the right solution for a car with low CdA, and ubiquitous fast chargers.
 

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And bulkier. The standard range Model 3 in China, and now Europe, is LiFePO. It is the same size and weight as the long range battery, but only two thirds the capacity.
I think I might prefer a LiFePO Bolt now that I am convinced of it's "around town" utility. Tangentially, for me, increased range is not a solution to "range anxiety" My real issue is with charger reliability and density. I really don't see this as being solved by any of the present offerings. 95% of my usage would be easily be met with 1/2 the range of the present Bolt. The 5% that is not is a real pita with anything on the market. The only thing that changes is how much of a pita.

I probably would not have bought into this idea prior to owning my Bolt. However if the option was a car that might last virtually forever if might change the metrics. I might be able to justify an around town only car.
 

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I think I might prefer a LiFePO Bolt now that I am convinced of it's "around town" utility. Tangentially, for me, increased range is not a solution to "range anxiety" My real issue is with charger reliability and density. I really don't see this as being solved by any of the present offerings. 95% of my usage would be easily be met with 1/2 the range of the present Bolt. The 5% that is not is a real pita with anything on the market. The only thing that changes is how much of a pita.

I probably would not have bought into this idea prior to owning my Bolt. However if the option was a car that might last virtually forever if might change the metrics. I might be able to justify an around town only car.
Given the density of charging stations on the west coast (maybe east coast too?), I would definitely prefer 2-3x more cycle life and wider temperature tolerance of LFP. Even if price of battery drops, the labor cost for replacement is still there. Best to NOT have to replace it. I wonder if Nissan had build the Leaf with LFP cells, might it not have the battery degradation problem in places like Phoenix.

 

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Given the density of charging stations on the west coast (maybe east coast too?),
Not enough DC fast chargers, by an order of magnitude, even if 100% reliable, which EA is nowhere close to yet. We travel to New York, and Tennessee with our Bolt, using this inadequate infrastructure. But if people who are not fanatics are going to do this willingly, we need much better infrastructure.
 
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