The DevilDog Weekly Update

[petefoss]

But other than more use of heater and lights - I notice no change in actual range with temperature - but you use heat and drive in the dark more in winter, and those do cost you.

Funny how the laws of physics apply <grin>.

[frankydude]

It's the heater, that thing can draw 7-8kw - that's a lot! When I don't use mine (not willing to do that most of the time, but I did test) the range was close to the same warm or cold.

I suggested on another post that the A/C electrically driven compressor should be equipped with a reversing valve, so the A/C becomes an heat pump. That would help to get the interior warmer for a lot less electricity from the battery. It would also need to have a defrost cycle by software control, to remove frost buildup.

[Rusty]

I suggested on another post that the A/C electrically driven compressor should be equipped with a reversing valve, so the A/C becomes an heat pump.

My understanding is heat pumps don't work well when there's a large deltaT between ambient and desired temperatures. For cooling you usually don't need much more than a 40° drop (that's 110° to 70°). But for heating you can have MUCH higher deltaTs, like from -25° to 75° or more (a 100° delta!).

So there has to be an electric heater to deal with that.

Could it have been a two stage design, so that in milder temperatures it could use the heat pump instead of the electric heater? I sure hope so, since that'd really help cool weather AERs here in SoCal. But I think that (along with using waste heat from the motors and transmission) is a Gen II Volt solution. Likewise I wish they'd use a heat exchanger to warm the battery from waste ICE or motor heat, instead of using the electric heater (when possible).

The Gen I Volt is years ahead of anything else out there in the market. And IMHO there are lots of ways to improve it, especially for cool/cold weather AERs. But the first order of the day is to get the thing to market!

[saghost]

I suggested on another post that the A/C electrically driven compressor should be equipped with a reversing valve, so the A/C becomes an heat pump. That would help to get the interior warmer for a lot less electricity from the battery. It would also need to have a defrost cycle by software control, to remove frost buildup.

I'm guessing that the last sentence is why the Volt doesn't have one. The EV1 system did use a reversing A/C-Heat pump to generate cabin heat, and I would assume that the Volt's HVAC is evolved from the EV1 design like most of the rest of the high voltage equipment. GM therefore clearly had a reason not to retain it - and I'm thinking that the tendency of the radiator area evaporator core (when running as a heat pump) to accumulate ice during typical operating temperatures for the heat pump in most of the US and Canada might be a large factor.

[Red Volt]

It would probably need to work like a house heat pump with electric strips, but I'm sure they looked at it a lot. It might have been better to just use electric heat and save wear and tear on the compressor. Also, there is the added complexity of reversing valves, etc. Without doing any real numbers, I can see where it's a complex scenario. And if it's real cold, the heat pump mode wouldn't serve much purpose.