Thor Forums

[Chance]

Originally Posted by Bob Denman

Thanks!
So now my question morphs into: "Would dual alternators provide faster charging capabilities for conventional systems?"

Depends.

Depends on type of battery, battery bank capacity, and (excess) alternator capacity.

For typical RV with a couple of flooded or AGM batteries, a single large OEM alternator should be able to supply as much current as the batteries can ideally take. Or close enough that it’s not worth the added expense.

However, if we start looking at newer motorhome designs like the Coachmen Cross Trek without an Onan generator, which has 330 to 400 Amp-hours of AGM battery capacity, then a single OEM alternator will not likely be able to charge as fast as possible. In talking with Coachmen, they told me they were ordering new 2021 Ford Cutaway chassis with dual alternators from Ford. And based on dirt cheap cost, every RV manufacturer should do the same in my opinion.

Once we start looking at 600 Amp-hours of lithium (using a single Lithionics battery as an example), then the higher alternator capacity the faster it can recharge. Maximum continuous charge current is 400 Amps which a single OEM alternator can’t do. Even 300 Amps (for 0.5C) is too much for single OEM alternator.

In fairness, second stand-alone add-on alternators may be heavier duty, and often have external regulators which can charge lithium batteries — hence the high cost.

Still, I’d probably pass on a $3,695 second alternator and plan to charge at campgrounds at least every other night. If alternator was OEM and under $500, then I’d want it even if I thought I could get by without.