Battery charger

Why do you need a battery charger? To answer your question, you would need a heavy duty battery charger, that is able to charge heavy truck batteries

 

try a farm store... a walmart charger would probably be fine. Just get something with decent amp output

 

I am not sure about that one. Call a battery dealer that sells commercial batteries, they will tell you exactly what you need

 

Ok, do you have the truck running when using the microwave?

 

I'd get something a little more heavy duty than that. It'll work but it'll be slower if the batteries are really drained. I'd get something capable of a 40-50 amp fast charge.

 

Slow/trickle charge is best which would be the lowest rate on the charger. Also depends on what type of batteries you have. Not all chargers will charge the glass mat (AGM) batteries. Here is one example of a more versatile charger for a little more than the one at Wal-Mart. It does not have a boost mode but 50A would be for a car and not a heavy truck. Alternator should be load tested preferably with the newer capacitance type testers that will also check ripple. Ripple is the amount of ac current that gets through the diodes. Alternators often get weaker over time (won't put out the proper amps) due to bad diodes not converting enough current from ac to dc.
Amazon.com : pro logix battery charger