Originally Posted by FastAl
I don't want solar.
My post was an amperage comparison.
As others have posted it all depends on the total Ah of the batteries you put in the van, how low they are, how much amperage your van itself uses. If you have added load, your stock alternator will take longer to charge and it will depend all that's written above and the alternators output. I found my stock alternator wasn't enough to supply a positive charge while driving with the normal engine load and the add on air conditioner running. I don't have a clue what the Sprinter conversion pulls amperage wise. If the alternator supplies enough to run the van and supplies a positive charge of about 10 amps that would be reasonable and should charge up a 440Ah battery bank from 50% discharge in a few of hours. Start kicking on things like an inverter, refrigerator or other items inside the conversion and it subtracts from the battery charging. A higher rated alternator is generally a good choice just because of all the extra load the conversion itself uses. Also alternator charging supplies a quick bulk rate but tapers off during the absorption state so they'll actually never reach full. As Greg pointed out, equipment like the Sterling alternator to battery charger
will better regulate the charge over what a stock alternator can. If you don't want solar the Sterling unit is a good choice.