Burning smell in exterior from just sitting in Park

A strong smell of burning plastic/rubber.

Reproducing the problem:
No smells. I start the car and put it in Park. No smells. 10 minutes passes. No smells. After about 30 minutes, the smell is noticeable. The only thing that seems to happen in between is the car starting every few minutes to recharge the battery.

I haven't noticed how much correlation there is between the smell and every time the engine starts to recharge the battery.

Heat/AC is off.

Other facts that may or may not be relevant:

• The smell is not present in the cabin
• There's nothing covering the battery vent in the back seat
• The smell has seemed stronger on the passenger side, but I can't say for sure if that isn't due to air flow around the car
• Engine oil and coolant levels (for inverter and engine) look to be full, no noticeable funny colors
• I checked the tailpipe/muffler and did not see obvious burned plastic bags/debris
• The smell doesn't seem to be coming from the exhaust itself - I took a few whiffs 1-2 ft from the tail pipe while the engine was running (mmm!) and the odor is not noticeably stronger
• The smell doesn't seem noticeably stronger when I stick my nose in the engine bay
• If anything, the smells seems the strongest when I'm crouching/standing on the passenger side of the car (maybe a smell emanating from under the car and a slight breeze blowing it toward the passenger side?)
• The car sat completely idle from March until September (ok, somewhere in between, someone jump-started it, drove it a few blocks, then let it go idle again)
• After I initially detected the smell from a 1-block trip and a lot of sitting in Park (to help recharge the 12-volt battery), I totally forgot about the smell and drove a 70-mile round trip where the car seemed to do fine. Afterward when I got home, my wife got out of the passenger side and was like, "What's that smell?"

 

Maybe I'll get under the car and take a closer look.

There's a ban, yeah, but I forgot what the exceptions are. For sure you can still buy plastic bags for like 10 cents. In general, there's been a rise in plastic bags being used at grocery stores due to some stores enacting policies against reusable bags for the protection of their employees.

Also I forgot to change my profile... I moved to Washington state a couple months ago. Some cities here have bans, some don't.

 

I seem to have solved the problem, although I don't know what the actual issue was.

Problem seemed to have gone away after I replaced the 12v battery.

I don't drive the car often and I didn't want to throw in $150-200 for a new battery if the burning smell was going to be a big issue. However, after some more testing, plus the fact that the problem didn't seem to occur until after my 12v battery issues, thought it was worth a try.

I hadn't driven the car for months so the 12v battery went super dead. I could start the car using a jump pack, but I instead kept it on a trickle charger. The trickle charger never registered as "charged" - was always in a red "charging" state, even after weeks, but it allowed me to hop in the car and drive. Could even drive the car the next day without plugging it back into the trickle charger.

The smell would start pretty consistently after about 25 minutes, where in between the car would start up every 5 min or so to recharge the traction battery. (I didn't know if that was normal or not)

However, I tried driving a few miles and back, about 15 minutes of driving - and no smell. I took this as a hint that the problem was related to the electrical system instead of the engine, since that drive definitely worked the engine more than having the car sit idle at 25 minutes (I actually tested with the car in regular mode and in maintenance mode and the burn smell started after about 25 minutes for both - test run on separate days).

After swapping the 12v battery, I tested again. I noticed the car rarely started back up to recharge the traction battery (only like 1 time). My guess is maybe due to the weak 12v battery, something with the electrical system was being overworked and burning.

Not sure if there's permanent damage done to something, as it seems a burning smell means something has been burnt. Oh well, I'll just keep driving until something breaks again lol.

 

lol, yes, I suspect it had something to do with the battery.

However, I'm not sure where the burning smell was coming from. Can batteries smell like burning? I didn't notice any visible damage on the battery I removed. Also I figured if the battery smelled, it would smell at least a little in the interior, but it never smelled the least bit inside, but very much outside.