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70kwh usable?

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OK, that says the regen is counted in the total, but if it is a net total in/out of the battery, regen will tend to cause the total to be smaller than it otherwise would be due to charging losses.

Say you draw 100Wh accelerating the car, then (helped by a slope) manage to regen 100Wh back into the battery: the total will now read zero. However, the battery will no longer be fully charged since it takes more than 100Wh of charging to offset 100Wh of discharge. I don't think anybody has managed to measure it accurately, but there have been estimates in the region of 10's of % loss on the round trip.

Of course, the total amount of regen in a long trip is normally a very small proportion of the energy used - though maybe in city driving it could become significant.

From many observations on a classic P85, 290 Wh per rated miles is the correct number for charging and 300 Wh/rated mile is the correct number for DC charging. If these are correct and the measurements are at the battery, then the difference is only 3.3%. The 10's of percent numbers tend to be for AC to DC or DC to AC conversions.
 
From many observations on a classic P85, 290 Wh per rated miles is the correct number for charging and 300 Wh/rated mile is the correct number for DC charging. If these are correct and the measurements are at the battery, then the difference is only 3.3%. The 10's of percent numbers tend to be for AC to DC or DC to AC conversions.

(assume typo for first 'charging' should read 'discharging).

Those are useful numbers. If we assume that the Wh readings are based on current measurements in/out of the battery (at the shunt which was observed in the teardown), then your 3.3% is the combined resistive and any chemistry losses across charge/discharge of the cells themselves. Per wk057's point about square law effects of the discharge rate, those numbers shouldn't be quite constant, but 1.6% is quite small.

The 10's of percent estimates I was talking about were in the context of regen energy recovery - to include losses in the motor/drive electronics - but of course those are almost certainly outside the measurement point we are talking about here, my mistake.

So while my original point is still valid, with your figure suggesting only 3% loss on a regen/burn cycle, and regen being typically a small portion of total energy used, that's a small number times a small number and so the effect is probably insignificant.
 
Over the last year I've gone from a full charge right down to zero 5 separate times (brief stops only). All consumed 73-74 kWh except for the one with highest average Wh/mi (315) at 71.7 kWh. This is consistent with previous posters' comments that the higher the average energy used, the less total battery energy available.

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This was quite early on when I got the car, now over a year ago and in cold weather even. I think 5.8 firmware still accounted for heating and newer ones don't because on 5.9 and newer I've never gotten anywhere close to that kWh before running out of battery.

Looking at some of those pics above at 73-74kWh you have the power limiter around 160kW, which means you had plenty to go yet. I think lowest I've gone is 70kW or so and reports on this forum had the power down happen around 45-50kW range. That's the best indicator after 0 to keep in mind for when to really stop :)