RegGuheert
Well-known member
TickTock has the best and longest detailed record of LEAF data that I know of. I was looking at his data yesterday and one thing that struck me was that his efficiency, from both the dash and the wall, has steadily dropped over the life of the vehicle. (That plot can be found second from the top in the above link.)
So I thought I would post to ask what are the main contributors of this drop. I can think of a few possibilities:
1) Driving style: Perhaps TickTock's driving efficiency has steadily dropped? I don't know how we could ever quantify that.
2) Battery electrical resistance: The resistance of the battery goes up as it ages. This effect will certainly lower the efficiency of the vehicle, but I haven't ever considered it to be something that could significantly effect efficiency. Let's run a few numbers to see:
Initial resistance: ~55 mohm
If you assume battery voltage to be 370V nominal and use a power level of 10 kW, you get a current of ~27A. The internal resistance of the battery would dissipate ~40W or 0.4% efficiency hit. Not much.
Let's assume the battery resistance increased by a factor of 4, then you would expect to get a 1.6% efficiency hit from that. Frankly, I doubt we could easily see the additional 1.2%.
3) Reduced capacity: Perhaps reduced capacity results in the average battery voltage being lower, thus increasing the current during all phases of a drive, increasing all resistive (I^2R) and IGBT conduction losses (although reducing some switching losses). I'm not sure how to quantify this possibility to see if it amounts to much, but perhaps it does.
4) Tires: I doubt it since I thought efficiency gets slightly higher as tires wear, but perhaps I am missing something.
5) Drivetrain losses: Are there any mechanisms which would cause frictional losses in the drivetrain to increase?
I guess I also feel like it is getting harder to maintain high efficiency driving our LEAF, but that could simply be how I feel after driving through a winter which was significantly colder than any we have had for a very long time.
Any other thoughts on where TickTock's (and presumably everyone else's) efficiency is going?
So I thought I would post to ask what are the main contributors of this drop. I can think of a few possibilities:
1) Driving style: Perhaps TickTock's driving efficiency has steadily dropped? I don't know how we could ever quantify that.
2) Battery electrical resistance: The resistance of the battery goes up as it ages. This effect will certainly lower the efficiency of the vehicle, but I haven't ever considered it to be something that could significantly effect efficiency. Let's run a few numbers to see:
Initial resistance: ~55 mohm
If you assume battery voltage to be 370V nominal and use a power level of 10 kW, you get a current of ~27A. The internal resistance of the battery would dissipate ~40W or 0.4% efficiency hit. Not much.
Let's assume the battery resistance increased by a factor of 4, then you would expect to get a 1.6% efficiency hit from that. Frankly, I doubt we could easily see the additional 1.2%.
3) Reduced capacity: Perhaps reduced capacity results in the average battery voltage being lower, thus increasing the current during all phases of a drive, increasing all resistive (I^2R) and IGBT conduction losses (although reducing some switching losses). I'm not sure how to quantify this possibility to see if it amounts to much, but perhaps it does.
4) Tires: I doubt it since I thought efficiency gets slightly higher as tires wear, but perhaps I am missing something.
5) Drivetrain losses: Are there any mechanisms which would cause frictional losses in the drivetrain to increase?
I guess I also feel like it is getting harder to maintain high efficiency driving our LEAF, but that could simply be how I feel after driving through a winter which was significantly colder than any we have had for a very long time.
Any other thoughts on where TickTock's (and presumably everyone else's) efficiency is going?
