This device will allow you to charge devices in the 15 -24 volt range at around 3 Amps.
This is a much more efficient way to convert stored energy in a battery to stored energy in you laptop( or to run another device) rather than through an inverter.
When looking for one of these adapters (which there are many designs) look at the adapter tips to make sure they will fit the devices you intend to use it to power.
Make sure the voltage is switchable and matches the voltage you need for your devices.
Not every possible voltage is supplied, common voltages are: 15 16 18 19 20 22 24
Many devices are voltage tolerant to some extent, if need be 1 or 2 extra volts work, if you cannot supply the exact voltage.
Make sure the power rating of the adapter is more than the power rating of the the device.
Check the polarity of the device and charger, usually the outside shaft of the adapter is negative (-) whereas the tip or inside is positive(+). Some adapters allow polarity changes on the tips.
The rating for the adapter can be between 80 and 150 watts.
The easy way to determine the power rating is to look at the AC adapter of the device and multiply the DC voltage and current together and that will be the power rating.
Cost 80W $25
Cost 150W $120
Cost of an obscure tip $3, time to find one, up to 6 months (be warned).
The sensation of success after a long determined hunt, priceless?