Battery voltage in the manual is listed as "nominal 350 volts", but that's not the numbers it has at 100% charge and 0% charge. What are those numbers?
What's the battery voltage from 0% to 100%?
- Thread starter timk225
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As the battery has 96 cells in series, I'd expect the resting, open circuit voltage to be:
0% indicated SoC - (really ~3% absolute SoC) - 2.85V * 96 = ~274V
100% indicated SoC - (really ~98% absolute SoC) - 4.15V * 96 = ~399V
The minimum voltage can be lower than this when discharging and the maximum voltage can be higher when charging.
0% indicated SoC - (really ~3% absolute SoC) - 2.85V * 96 = ~274V
100% indicated SoC - (really ~98% absolute SoC) - 4.15V * 96 = ~399V
The minimum voltage can be lower than this when discharging and the maximum voltage can be higher when charging.
I see, thanks for the numbers. Quite a range it can operate in, I do notice the car being slower to accelerate hard when at low SOC.
Power is Volts X Amps. So strictly speaking Voltage does not matter. Just use more Amps to get same power.
But there are limits to Amperage available in some cases. At low state of charge the Amps are limited to prolong battery life. Same for cold weather.
Same for regen -> putting energy (charging) back into the battery while decelerating. Regen is limited in cold weather and at a high state of charge.
But there are limits to Amperage available in some cases. At low state of charge the Amps are limited to prolong battery life. Same for cold weather.
Same for regen -> putting energy (charging) back into the battery while decelerating. Regen is limited in cold weather and at a high state of charge.
Yes, I have noticed that if I am driving at highway speeds at low SOC, I'll get a few dots on the right side of the power bar, indicating that maximum discharge is being limited. It didn't do that, if I remember correctly, back when I first got my 3 last May, it came along in the course of updates.
That one time (I wrote about it here) when I had to drive 25 miles home from work, with 13 indicated miles of range left, after the battery sat in sub-freezing cold for 8 hours, the dots got most of the way to the middle of the power bar from the right side!
Over the 8 hours, the cold reduced it from 30 miles to 13.
That one time (I wrote about it here) when I had to drive 25 miles home from work, with 13 indicated miles of range left, after the battery sat in sub-freezing cold for 8 hours, the dots got most of the way to the middle of the power bar from the right side!
Over the 8 hours, the cold reduced it from 30 miles to 13.
Jedi2155
Model 3 has Arrived.
MarcG
Active Member
Reviving this thread now that I have Scan My Tesla setup.
From my CAN bus readings over the last several weeks, maximum pack voltage has always reported 403V, and minimum pack voltage varied between 240-242V.
The bottom voltage probably includes the buffers, which we now know is around 4.5% of the total pack capacity (my readings show this to be 4.45 to 4.46%). So voltage at 0% SoC as reported by the BMS is probably closer to 252V.
I haven’t done a 100% charge since acquiring the SMT setup, but I don’t see a reason why there should be a top-level buffer. I’ll confirm that next time I do a 100% charge by reading the voltage at rest (not charging or discharging) while at 100% SoC.
If it indeed shows 403V at 100% SoC, then the max pack voltage has been reached and there is no top-level buffer. I can do the same thing to calculate bottom-level voltage by driving to 0% SoC, but that might be a while longer.
If someone with a CAN bus reader setup has already done this, I’d love to see a graph showing pack voltage over the entire SoC range.
From my CAN bus readings over the last several weeks, maximum pack voltage has always reported 403V, and minimum pack voltage varied between 240-242V.
The bottom voltage probably includes the buffers, which we now know is around 4.5% of the total pack capacity (my readings show this to be 4.45 to 4.46%). So voltage at 0% SoC as reported by the BMS is probably closer to 252V.
I haven’t done a 100% charge since acquiring the SMT setup, but I don’t see a reason why there should be a top-level buffer. I’ll confirm that next time I do a 100% charge by reading the voltage at rest (not charging or discharging) while at 100% SoC.
If it indeed shows 403V at 100% SoC, then the max pack voltage has been reached and there is no top-level buffer. I can do the same thing to calculate bottom-level voltage by driving to 0% SoC, but that might be a while longer.
If someone with a CAN bus reader setup has already done this, I’d love to see a graph showing pack voltage over the entire SoC range.
I think you've assumed that voltage varies linearly with SoC, but that's not really true for Li-ion cells (and many other types). I could be wrong that you made this assumption, rough head math makes it look like this is what happened though. See this very generalized graph for what I mean: https://www.powertechsystems.eu/wp-...1/LiFePO4-vs-Lead-Acid-Discharge-Curve-EN.png
Anyhow, I think I recall seeing 4.195 on the cell voltage with Scan My Tesla (definitely 4.19x) at 100%, which somewhat confirms there's not really any top buffer. Can't recall what that was on total pack voltage, but I've definitely seen 4xx.
This graph is a Tesla 2170 cell discharge curve at 0.25C from Jack Rickard. Multiply this by 96 to get the pack voltage.
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