AC to heat pump conversion?
Posted by wwhuman@reddit | projectcar | View on Reddit | 9 comments
Hello everyone, I’m looking to modify my ICE car to be able to camp in (among making it into a hybrid and wanting to overland/roadtrip it for extreme distances).
Is it possible to convert my old AC system into a heat pump system? I’m already switching to an electric compressor but want to try to keep the in cabin modifications to a minimum.
My current idea is to leave the heating to the engine while driving but I want to be able to heat during the night without running a fuel heater or the engine.
I know it’s probably not worth it, but thought I should ask as this project is kind of like a pipe dream anyways
Ghost17088@reddit
How long are you wanting to be able to run on battery? Because you’re going to need a pretty large battery to run AC all night without the engine. As for heat, get a heated blanket. It will use way less energy to keep you warm than trying to keep the whole car warm.
wwhuman@reddit (OP)
That is probably what will be happening at least in a nearer term. The goal is to put the equivalent of a gen 1 leaf battery in it, so it being able to run the whole night wouldn’t be a problem. If I was not doing the nightly ac/heat I would probably be able to do half that size. 10kWh or 22kWh, honestly that is a thing I’m still deciding on.
Ghost17088@reddit
Don’t Leaf batteries have degradation issue due to only using passive cooling? Also, if you’re talking about the Saab, you’re going to eat up about half of your cargo weight limit in battery. You’re also going to have to make your own custom controls for the battery and HV system because that battery was made for an EV, and you’re going to make a hybrid powertrain for it. Quite honestly, a heat pump is the least of your concerns on this build.
wwhuman@reddit (OP)
Yeah but used leaf battery modules are cheap af, and I see the powertrain as a fun challenge, though honestly exactly which battery I end up with will probably depend on what’s available for cheap from the scrapyards, designing around a leaf battery currently is mostly just for reference. Weight might be a concern, car will have to do some dieting and I’m doing a spare tire delete as well.
I think(read hope) that it will fit under the floor if the boot where the spare tire currently sits
Ghost17088@reddit
They’re cheap because they are degraded and don’t hold full/any charge.
wwhuman@reddit (OP)
From what I gathered they usually have 80% of their original capacity when they get sold off. Honestly it seems like a big reason they're cheap isn't because they're degraded, but that the vehicles already had such bad range when new so nobody wants to replace their old cells and choose to upgrade instead. (80% of dog shit is even more dog shit). Especially when building your own pack (i.e. mixing modules from multiple vehicles) it's good because a big reason packs fails is that just one of all the modules is not at the same state of health as the others.
If I was building a full EV they would absolutely suck though, the OG leaf sucked ass.
Ghost17088@reddit
Yeah, I definitely haven’t worked on cars for the last 20+ years and EVs for the last 8. You got this!
ColonelTermite@reddit
I don't know how cold you're thinking of camping in. If it's colder than a sweater and extra blanket would cover, I don't know if a heat pump would handle it. As we learned here in Virginia this winter, heat pumps suck and get real inefficient when it gets really cold.
This is not my area of expertise, and I have a rudimentary understanding of how they function, so I'd send you to one of the hvac subs for better information.
That being said, I'm thinking you need a compressor that can somehow reverse direction, pressure regulators in the right spots that can also reverse, power to the cooling fan as well as blower for when engine is off, and run it on a thermostat. Ideally, wire it in a way that it disables and let's the car brain handle everything when the engine is running.
Or, fabricate a bracket that can hold a small window AC/Heat unit that can be wedged in one of your rolled-down windows, and run that off an inverter. That's what I'd do, but this is your pipe dream and not mine. I wish you luck either way.
wwhuman@reddit (OP)
Honestly I’m trying to built it to make a trip from Europe to Eastern Asia. >!Currently that would be geopolitically impossible but let a girl dream, maybe in the future when the world is less chaotic!< so basically want it looking pretty much stock from the outside to keep various officials at bay. The thing also has to pass inspection.
I saw that there might be a need for aux heat and honestly at that point I think it would be better to just run the engine