On 06/12/2018 22:09, Roger Stockton via EV wrote:
Steve Heath wrote:
The best mile/Kw I have got has been 180 and the worst is 230. Average
is 190 and this measurement is based on coulomb counting over the
distance.
I think you are meaning to state 180-230 Wh/mi? 180-230 mile/kWh would be
extremely unusual efficiency for an on-road EV, and mile/kW just doesn’t make any
sense ;^>
I am currently in detention for the typos...
If I use the capacity used based on voltage then it can get very silly.
I was getting figures of 600-700 w/mile because the voltage vs soc is
non linear. I could drive 25% of the range and the capacity would drop
to 50%. This did not make sense so I stopped using them and fitted
coulomb counters. I do use the voltage to predict low battery but the
rest of the data is just a rough guide. The gauge does look pretty on
the dash though.
I understand your reasoning for not using battery voltage to estimate state of
charge, but when you quote any efficiency values involving Wh or kWh (Wh/mi or
mi/kWh), you are, of course, taking battery voltage into account because power
depends upon both the battery voltage and current, and so, therefore, does
energy in Wh or kWh.
Pure coulomb-counting will only give you energy usage in mi/Ah, which may be
useful in the context of your own EV, but does not allow comparison to the
usage of other EVs.
Yes you are correct that coulomb counting is only part of the
measurements. The meters I use measure the voltage at the same time and
calculate the power, and so on.
So my EV did a 29 mile journey last night and consumed 117 aH battery
capacity and 5.7kW which works out at 196wh/mile.
Cheers
Steve
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