Let's say I want to have a spare car battery in my car.....

[Garber46]

Yeah, I have the NOCO and I charge it every two months and it'll start the car right away. Best investment ever

[DMG]

So if I set a good car battery in the passenger footwell, so I have a way to self-jump my car if I end up in the middle of nowhere with a dead battery; is it feasible to use a set of alligator clips on the battery, and a male plug into the cigarette/accessory socket, with maybe a trickle charger in the middle? Just to keep the spare battery topped off.

I looked around Amazon a bit, not seeing it, not sure of the terminology I need.

Plenty of trickle chargers for plugging into the house 110 line. I suppose I could stick a 12v to 110 converter in the socket, then plug a trickle charger into that, and run that to the spare battery alligator clips, but I'm looking for something more elegant, that doesn't have to convert from 12v to 110 then back to 12v.

Anyone with knowledge or experience they can share? I want my running battery to share with the spare, but I don't want them to both go flat at the same time. Just a 1-way power trickle to keep the spare at 100%.

A 60 pound battery, especially a lead acid battery loose in the passenger compartment can turn a minor accident into a fatal one. Find a place under the hood and mount a battery there. You can separate it from the main battery with a manual or automatic switch.

Post up the make and model and I will likely be able to suggest a second battery location.