Ideally you'd have a removable power module which you can take from device to device... a "zap drive". Brought to you by the US Nucleics Corporation.

They can be shaped as coins and become a new currency, it glows green when fully charged. Devices(including cars) have coin slots to take in power.

Spoken like a true geek. Normal people don't want to know that such things even exist. Let machines with radiation detectors track them down in the dumpsters.