A couple power supply theorys

[Metallover]

I have been thinking about a couple things that could be used or modified to be used as a powersupply. First off is a power inverter. The ones used in cars that run 12v input into a standard 120v home outlet. I thought the inverter could be used backwards somehow.

The other one is a car battery charger. Can it be hooked up in any way to where it could supply power to my charger?

At the moment I'm using a sla battery and it works fine, but I am going to start using those for my electric bike when that's finished so I'll be needing a power supply. If all else fails, I might be adding a power supply to my next purchase at hobby city.