How to power a laptop from a cigarette-lighter outlet
Although manufacturers sell 200-watt inverters, most cigarette lighter sockets only crank out 96 to 120 watts. Check the wattage shown on the laptop power supply (or whatever other device you want to power) to find its wattage. If yours is 90 watts (typical for a full-size laptop), you've already maxed out the typical car's lighter socket. If you need to power two laptops, don't add a power strip or octopus adapter. Adding a second power supply would overheat the inverter and most likely blow the cigarette lighter fuse. Instead, buy a second inverter and plug it into a different socket if you have one. The bottom line is that you can power up as many devices as you want as long as the total doesn't exceed 100 watts.