I'm confused:
You need the right kind of volts and the right amount of current (amps) to charge, or real-time run, your laptop.
You can get these two things from a charger/adapter for your laptop that is powered from a 120 volt alternating current wall outlet or that is powered from your RV battery(ies).
i.e. My HP laptop uses an OEM HP charger/adapter made for it. This charger/adapter can be powered from either a wall socket or from a 12V vehicle receptacle. What the charger/adapter does is make the proper direct current volts along with the necessary direct current amps for the laptop. It was very expensive when I bought it new along with the new laptop. Now the laptop is old. It's expensive OEM charger/adapter failed a couple of years ago. I went on eBay and bought an identical - in original packaging - OEM HP labeled charger/adapter for it for around $18. The price was low because the laptop is obsolete (in some people's eyes), so "nobody" wants one of it's once-expensive charger/adapter gizmos.
A little more info regarding your setup would be useful.
I suggest you go on eBay and look for the exact charger/adapter intended for your specific model laptop. Amazingly, somone just might have an original one in new, or near new, condition that they'll take peanuts for ... as compared to it's original retail price.
