I have a Black+Decker car vacuum. I've had it about 5 years, but have only used it a couple of times.
It didn't have any effect on the battery as far as I could tell. The advantage of a car vacuum instead of an extension cord is that you can pick up messes when you aren't at home.
The few times I used it was when we spilled something when we were far from home, and it managed to pick up everything without me getting my hands dirty.
I wouldn't use it for day to day cleaning, because while it's powerful enough to pick up most dirt, it's not so powerful that you'll have a clean car with one pass. We've got pets, and it'll take a fair amount of work to get their hair off all the mats.
Likewise, the crevice tools will work to pick up dirt in those hard to reach spaces, but they're not flexible enough, and the vacuum isn't powerful enough to clean all the nooks and crannies well.
My vacuum is something like this one.
https://www.amazon.in/Black-Decker-NV1210AV-Cleaner-Accessories/dp/B07H7MMLSF
It's nice to have, but seeing how little I've used it, I wouldn't buy it again.