I have a mid-sized Alpine unit, plugs into the cig lighter, got it 4 years ago.
Used in the truck, on the boat, and in the RV trailer.
Mostly charges cell phone/camera/computer/etc batteries.

The dividing lines seem to be what you want it for...
For small battery chargers only,
For heavy chargers like laptop pc's and power tools,
For power tools.

Don `87 Mitsu 2dr, Rubicon survivor, GModified.