13 volts / 900 watts the converter will want is about 70 amps. This will be what your alt needs to put out to power the converter and a discharged camper battery
What size wire is going from your inverter in your truck to the batterys.
1. Even 2 gauge wire will get warm. Ask me how I know.
2. Unless you have tow package I doubt your alt puts out 70 amps. Or its just 70 amps. I think the tow package tacomas put out 130 amps.
Your better off just using jumper cables from truck battery to camper battery..
If you do insist on trying it, please try it at home,.
This way you dont get stuck in the woods when the alternator over heats and stops working.
Hope your fused properly too... Electrical fires are no fun...