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Discussion Starter · #1 ·
I have noticed that when I use the pre start options to defrost and warm the car the battery get an additional charge that sometimes lasts for 45 minutes. Given the car is plugged in all the time when parked and the pre start option is for 10 minutes this is a pain as it means to ensure a fully battery I have to "waste" one pre start session just to find out how long it will take the car to reach full charge.

I would have expected the monitoring system to maintain a full charge so the car was ready to go when I wanted to use it.

Any one else noticed this? Am I being unreasonable in my expectations during this cold weather?
 

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Hi Ray,
Yes I get the same, I think it's quite comical that the car uses the battery charge to "warm the car" which by the time you are back to a full charge the car interior has cooled down again, or am I missing something?

Gary
 

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Discussion Starter · #3 ·
Hi Gary,

I thought the car was supposed to use electricity from the mains when the pre start was in operation not from the battery?
 

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RayG said:
I thought the car was supposed to use electricity from the mains when the pre start was in operation not from the battery?
The pre-start may draw more current than the mains charger can supply. sorry, I can't remember the exact figures but I think a 16amp circuit may be able to supply enough current whereas a 10amp or 6amp circuit cannot. When that happens it will use both the mains and the battery and then re-charge the battery.

A lot of the initial power draw is to get the battery up to operating temperature, so if you pre-start, let the car recharge, and then pre-start again the second time round the battery will be warm so you won't lose as much charge. If you don't pre-start you'll have a much higher drain for the first few miles as the battery is heated.

Alternatively use delayed charging when you know your departure time and then the battery will be at temperature but the cabin will be cold. I suspect the best all round is to use delayed charging to complete about 20 minutes before departure then pre-start just after it has completed then give it a few minutes to recharge a bit. On the other hand I'm still not sure that pre-start really helps the range much.
 

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I have used prestart and also not used it and I see very little difference in range. I have now decided not to bother.
 

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It's useful to clear frost in advance but you have to time it right.

I've heard it can pull 5kW, so if true the battery could be supplying half the power even on the mains at 10A.
 

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It definitely pulls less power on the second pre-condition cycle, did it this morning to clear and demist the car before going out after all the frost last night. All fits with the explanation above.
 

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Tried pre conditioning at 6amp and used 2 miles from expected range, later tried pre conditioning at 16amp and used 1 mile from expected range.
Temperature in garage was minus 2 degrees C and cabin was set on auto, comfort. Started with 33 miles expected range and finished with 30 miles.
Dissapointedly, the charge to the battery was not replaced after pre conditioning because the car is set to a delayed charge (economy 7)
It appears from my un-scientific experiment that a good part of the energy comes from the battery and not all from the mains.
Does being plugged in at 6amp or 16amp make much differance to whats used from the battery?
Has anyone checked what wattage is used from the mains compared to wattage used from the battery during pre conditioning at 6amp and 16amp?
Would be interesting to know. :)
 

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I've worked out and confirmed tonight that it's best to do 2 pre-heats and leave a short gap between them. The second one doesn't need to use as much and the recharging of the battery afterwards 'stirs it up' and tops it off, meaning you get a bit more range than had you finished charging a while before.

By doing this I got almost as much range as in mild temperature, even though it was 3C outside.
 

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I think having the 16A wall-mounted charger reduces the impact of pre-heating. I see about 0.1KWH used at most. Normal journey being 4m each way daily means I can be cavalier about it anyway.

The down-side is that the range prediction is now down to 27 miles on full charge - but I still get 34 or so when I drive straight off onto a longer journey that uses all the battery. I hope it goes back up in the spring.

(I do use full throttle as well btw.)
(No - not ALL the time)
 

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Thanks dpeilow and RickMGoldie for the reply.
It seems the pre conditioning does not take too much power from the battery. Will continue using the 16amp charger to minimize usage from the battery and maximise usage from the mains.
 

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Used two pre con this morning and left to top up charge and almost got 40 miles EV today - just 0.5 short! Still quite good for the weather today :)
 

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I think I've perfected the art of the pre-heat.

I've tried a few techniques in the past few days and by doing two pre-heat cycles and then allowing the battery to finish recharging just as I want to use the car, I've been able to get almost summer levels of range. This was with the temperature at 2-3C.

At 10 Amps after the second cycle I find it takes just over 5 minutes to recharge once the pre-heat shuts down. Don't go too early or you'll miss a mile of range. Go too late and the car has cooled down again - even after ten minutes.
 

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dpeilow said:
Don't go too early or you'll miss a mile of range. Go too late and the car has cooled down again - even after ten minutes.
This is the problem I am having with pre-heat... I seldom know within a few minutes when I am leaving. Quite offten I have to go out NOW or else I know I will be leaving at a particular time and cannot get organised enough to work out when I must start the first pre-heat and then remember to start the second and that if it is even convenient to do so given that there is no internet control like there is with the Leaf.

I am sure that if you do it right and leave within a few minutes of it completing the charge then it makes a differece as David says but that will never happen for me and given the degree of faffing about you have to do to achieve it I suspect it won't suit most people... which makes pre-heat pretty much a waste of time for me and many others.

The only thing I find it of benefit for is warming the cabin but then only if I remember or have a 15 min warning of departure and can get to the car to set it off.
 
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