Battery data and what to do with it

4.3 volts at 100% SOC? That seems high. I would expect 4.2 volts per cell max. I wonder if there is an offset or an error in your CAN decoding.

 

Did you continue recording after the charge ended? What was the voltage 30 minutes after?

 

I would say no, but I could be wrong.

When charging near 100%SOC, this is the constant voltage phase of charging. This is when the charger is holding a specific voltage and as the cells charge up and their theoretical open circuit voltage approaches the charging voltage, the current goes to zero. Therefore at 100%SOC, the cell's open circuit voltage is very close to the charge voltage (but not exactly because the is also a current cut-off point when charging). With typical Panasonic lithium ion 18650 cells, 4.20 volts is the maximum charge voltage with a 100mA cut-off. For example, see this datasheet: https://industrial.panasonic.com/cdbs/www-data/pdf2/ACA4000/ACA4000C50.pdf

Another way to check this would to to look at the supercharger data. When I supercharge my car, I never see much beyond 352-353 volts at 100%SOC. 352.8volts/84cells in series = 4.20 volts.

All that said, this could change in the future with new chemistry and new additives in future cells. I believe Tesla has made some breakthroughs in cell additives that allows them to raise the 100%SOC safe voltage. But the old 60 and 85kwh batteries in the 2012-2015 vintage model S use older Panasonic chemistry similar to the one I posted.

 

Is this a classic 60 or a modern 60 (limited 75)?

I wouldn't have thought you'd see voltages nearly that high on a modern 60...

 

I took a quick look at WK057's Can bus Deciphering document Version 0.1. If this is what you are using to decode, you are correct that he doesn't mention an offset for Bytes 1/0 on Can Frame ID 0x0102. But he does mention that he had a limited data set to work from, perhaps the 60kwh cars have an offset. Could you post an example CAN frame?

 

Well, c4 8c does come to 36036. However, I still don't think it's correct. I suspect there is a -1000 offset, however until I sniff the CAN bus on my car, I can't be sure. Have you observed the pack voltage while supercharging? Does it correspond to what you are seeing on the CAN bus?

 

OK. Looking at this picture, this is why I am skeptical of your CAD data calculation. Notice 351 volts at 100%SOC. I am thinking there must be differences in the way the 60 cars report battery data on the CAN bus versus the 85 cars.

 

Unless you can get into the Diagnostics screens, the car will not report pack voltages while charging from an AC connection. Only DC fast charging from a supercharger or Chademo charger shows pack voltage, and only on older firmware (anything prior to FW8.0).

 

Some third party phone apps still report Voltage during DCFC including Supercharging - Remote S is one that does.

 

Ok. I don't use Remote S or newer firmware, but good to know.

 

Another stupid 8.0 regression...