"Warming up" in hot weather to protect battery

Yeah I do it quite often and have been offering this advice for ages. Just leave it in "P" and let it warm up in for about 40 to 50 seconds (doesn't matter if AC is on or off) before you drive off. It definitely helps preserve the HV battery charge.

 

I started the one minute warm up several months ago and have found no ill effects. It doesn't seem to badly affect the fuel mileage and the car is more responsive from the get-go being able to actually transmit engine torque towards getting the car moving.

 

Yeah it can go either way, but warming up doesn't seem to hurt my mileage either. Where I live I've got a small hill to climb and then the chance for a fairly nice half mile+ glide with slight downhill to flat terrain. If I don't warm up then I usually end up "squandering" all my SOC getting up the small hill and then I can't make the most of the glide opportunities that follow.

In my experience the warm up works best if you need to either climb a hill or accelerate quickly onto a main road in the first minute or two of driving. If you're lucky enough to have only slow easy driving and flat terrain in the first minute or two, then warm up is probably unnecessary.

Certainly I would recommend that if anyone regularly notices their SOC dropping to 3 or fewer bars in the first few minutes, then they should give the warm up procedure a try.

 

This is my understanding:

During the S1a warm-up cycle, the computer uses almost no ICE power unless you really need it. It does this to limit emissions of pollutants while the catalytic converter is still cold (I presume). Therefore, when you drive off right away, it is basically using all electric power, meaning it drains the battery. None of that gas being used in S1a is going into vehicle propulsion. If you drive off and drain the battery, the ICE will have to make up for it later somewhere.

In short, not only do you use the same amount of gas whether you wait until S1a is done or not, but you may be actually producing less pollution by waiting for the warm-up to conclude (because if it does have to rev up the ICE due to driver power request, it pollutes real bad).

If you want to sit in P during the warm-up, watch the MFD power screen. When the arrows pointing into the battery go away (so no arrows at all), then S1a is done (usually about 60 sec. if the car was not driven recently). The engine will still probably be running, but it is now in S1b and will use the ICE as it sees fit. If you listen closely, the engine will sound different when it goes into S1b (slightly higher rev).

 

+1

In addition, the HV battery is being charged during warm-up only if the car is in park. Overall one should get better fuel economy by warming up in park - I do it on every trip. Good luck!

 

I have a three block drive through my neighborhood before reaching a 45 mph thoroughfare. I start and drive slowly for these three blocks. By the time I reach the thoroughfare the car is usually fully warm, except for on the coldest mornings.

 

Is it warm enough to stop the engine when you reach the thoroughfare (assuming you may need to stop before entering it)?

 

Yes, the engine stops when I pull up to the stop sign at the throughfare. So I know the engine is warm and ready for the acceleration that I need to merge with the 45 mph traffic.

I also monitor the engine coolant temperature on SGII to be sure, especially on the colder mornings.