Recent content by randall_s

Because calendar aging is the issue, your aim is to maximize the amount of time spent at lower SOC (55% or below) while still having plenty of range for unplanned errands or emergencies. What I would suggest is to schedule your charge such that you leave for work with 70%-80% and arrive home...

I just wanted to add that I remembered (and posted here back in 2017) a similar incident when my car was less than one year old. I parked and lost about 5% over two hours. I'm guessing the BMS gets better readings as the battery cools and settles without load. So maybe this is typical...

Had a similar issue just today. Got home with 18%. Waited 3 hours before charging at it was at 11%. About 60 F in my garage. Hooked up SMT and took some readings in case they may become useful. I had 2 modules with around 18 mV cell imbalance, but don't know what to make that. Nominal remaining...

I owe you an apology. It's 318 wh/mi. I took a trip today and caught it dead on.

I'm addressing charging, not discharging. Most batteries can discharge at much lower temps than they can charge.

This is very useful for EVs sold today with this chemistry. The obvious next question is what's primary cause of the degradation over time? I would be surprised if this hasn't already been identified and addressed at the lab stage. Here's one article about a "million mile battery"...

I pulled a few spec sheets, but haven't gotten hard numbers on minimum charge temp. Onc says the electrolyte freezes at -60F. It seems that the lead acid battery can freeze if discharged, so it's important to keep it topped up. Maybe charging in -20F or -30F is OK as long as it stays topped...

https://batteryuniversity.com/article/bu-410-charging-at-high-and-low-temperatures https://blog.epectec.com/battery-charging-and-discharging-at-high-and-low-temperatures This reference shows it can be charged at -40C. If that's true, this isn't an issue at all...

If you look at an LFP voltage graph, you'll see that it's very flat. Because of this, the BMS can't accurately determine the SOC from the resting voltage through most SOC states, but it can determine when you reach 100% SOC, where the voltage rises steeply. After a 100% charge the BMS measures...

I looked at the abstract and found this part interesting. Later on: and in the conclusion: So it sounds like he developed a way to measure the activity of the silicon in the anode using hysteresis measurements and it was the primary culprit for the low SOC cycle degradation. The batteries...

Thanks for the response. 310 is rated efficiency for the S P90D as determined when I got it in 2016. I've "driven over the line" hundreds of times over the last 8 years and it definitely crosses at 310. I hooked up SMT and confirmed the 74 kWh (73.7 now) nominal and 4 kWh buffer. Gotta love...

Just for fun, I took corresponding photos: .307 kWh/mi x 176 miles / .72 = 75 kWh If I changed display to rated miles, it says 170 miles. .310 kWh/mi * 170 miles / .72 = 73 kWh The difference might be due to rounding errors. 72% could be 71.5% or 72.4%. 170 miles could be 169.5 miles or...

The rate Not at all. Please don't read something that's not there. I planned for 20% degradation when I purchased the car and I have 2 others newer ones. The OP was about calendar aging, but this has turned into reported capacity and range calculations.

I wouldn't be surprised to find that at all and most users report this. I don't think using this figure while driving is an accurate way to measure energy usage. There is too much variation in power, fluctuating temperatures, switching between regen, auxiliary systems, etc. The BMS is doing...

Even though the EPA tests use full depletion doesn't mean Tesla uses that figure in the calculations. You say they do - do you have a link? If that were true (74 kWh used being below 0% into buffer), the calculations at different SOC would not work out as they do. This doesn't appear to be...