giallo wrote:
Modern cars do just fine keeping the heater, AC or whatever else is electrically powered going while the engine has stopped. My current car has done so without issues for over 100k miles. The car is smart enough to start the engine should that be needed. That isn't very often at a standstill.
giallo, PeterCC -- you guys are talking past each other. Maybe I can clarify, or maybe I will just make things worse.
Generally speaking, cars with internal combustion engines use mechanically-driven AC compressors (literally driven by a pulley from the spinning engine). For heat, they generally steal some heat from the engine coolant (which would need to be cooled down by the radiator anyway). This is how it's been done for many decades. In the case of heat, it's probably been done this way for 100 years or so.
Cars that shut down automatically at a stoplight either lose AC and heat while the engine is stopped, or they must take some fairly drastic measures to make up for the loss of the mechanisms they have traditionally used. Specifically, they have to use AC and heat that is powered electrically instead of mechanically. AC compressors in particular, though, are extremely power-hungry, and so you'd typically not run that solely off of a standard 12v car battery.
If a car can run AC and heat while the engine is stopped, it either has a much larger battery, or it can only do so for a very short time. Likely as not, a car that can run those systems with the engine off is a hybrid, and has an onboard battery larger than a standard 12v car battery.
It's unlikely you'd find a non-hybrid internal-combustion-engine car that can run AC and heat without the engine running. It's not out of the question, and I'm sure someone will point one out just to prove me wrong, but that would be the exception to the rule.
Electric cars are in a similar boat here -- they lack spinning engines at all, and so AC and heat
must be provided electrically. Electric cars have an advantage, though -- a battery so large that you can run the AC for hours at a time without running out of juice.
I hope that makes things clearer.
⚠️ Last edited by jess on UTC; edited 1 time