Battery charging to "102%"?

gordo · Aug 17, 2015

You know that scene in "This is Spinal Tap" where the guitarist is explaining that a particular amp goes to '11' and Rob Reiner asks him why not just make 10 louder? Clearly, Tesla UI Engineers know what I'm talking about, but I have the reverse question with regards to the way my car counts backwards from 100% charge...

When I left for a trip last weekend, I pulled the plug at '100%', but with about 10 minutes estimated to go on a 64amp charge -- so not even a *full* 100%. But I'll be damned if the car didn't sit at 100% for like the first 5 miles or so before counting down normally after it hit 99%. It's as if the car actually charges to like 102% or so. Is this normal, and if so can someone explain why the percentage point between 100 and 99 would appear to defy the laws of the mathematics/physics/the universe?

Matias · Aug 17, 2015

It is just that is difficult for BMS exactly say, when the battery is 100% full. So 100% isn't exactly 100%.

Sparrow · Aug 17, 2015

My A type pack is probably way out of balance as it charged up to only 231 miles on a full charge, but did not lose any rated miles until I had driven 19.5 miles.

mknox · Aug 17, 2015

Not in my experience. My car usually starts dropping miles immediately. Sometimes I'll lose the first mile just a couple of blocks from home.

- - - Updated - - -

Sparrow said:
My A type pack is probably way out of balance as it charged up to only 231 miles on a full charge, but did not lose any rated miles until I had driven 19.5 miles.

Wow. Opposite of me. Not that I'm willing to try, but maybe I see those miles when my car reaches "0" (i.e. I can go another 20 after it hits 0).

gavine · Aug 17, 2015

Mine does this as well and there have been detailed discussions about why it happens. Last time I charged to 100%, it didn't start going-down until about 7 or 8 miles of driving.

Vip · Aug 17, 2015

Mine did the same just a couple of months ago. But after the first 5-7 miles it seem to have gone down a little quiker than normal. Thought everything was just balancing out.

ozweepay · Aug 17, 2015

This is likely done in software where if the charge exceeds some threshold, the software displays "100%." That way, if the battery ages a little and loses some capacity, it will still be possible to get it to "100% charge". I think the emotional impact of not being able to reach "100%" in a few years would be severe, so the software helps you out.

SmartElectric · Aug 17, 2015

Sparrow said:
My A type pack is probably way out of balance as it charged up to only 231 miles on a full charge, but did not lose any rated miles until I had driven 19.5 miles.

A pack here with 60,000 km and two years in. Supercharged to 100% recently and drove away when SOC was 100% and rated was near 410 km, but car was still charging at 12A 3xxV, so not "completely full".
Drove 7 km before rate range started dropping.

Todd Burch · Aug 17, 2015

This is why saying "I lost a mile of range" just because the battery charged to x instead of x+1 means nothing. Predicting range remaining is difficult. There's going to be variation.

Khatsalano · Aug 17, 2015

The first time I range charged in my S85D, I got 278 miles of rated range on the screen. It's EPA tested for 270. Of course, since then, I now get about 262 RM at 100% after 17,000 miles.

- K

KevinMS · Aug 18, 2015

Sparrow said:
My A type pack is probably way out of balance as it charged up to only 231 miles on a full charge, but did not lose any rated miles until I had driven 19.5 miles.

Went on vacation to the Oregon Coast last week. Put a range charge on my Type A pack (first time in about a year) both going and coming back. Got EXACTLY the same characteristics, 230 rated miles and drove 15 before any reduction. Ideal was 265 miles. As others have stated, I suspect the software is a little off. But I generally arrive at the destination with the margins expected.

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Battery charging to "102%"?

gordo

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Matias

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Sparrow

S105/ Roadster 189

mknox

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gavine

Petrol Head turned EV Enthusiast

Vip

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ozweepay

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SmartElectric

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Todd Burch

14-Year Member

Khatsalano

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KevinMS

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