Hi Tom N,
I think you mean an alternator, not a generator. And charging in a self propelled motor home can be fast--but NOT necessarily so from a tow vehicle to a trailer or 5th wheel. Those might be as low as 3 to 10 amps.
Also alternators can fail if they are pushed past 1/3 of their maximum output for very long. In my case I have a way to limit output. Most folks don't.
Not to mention that when the engine is NOT running--well idling to charge is a poor idea, and fairly pricy. In Canada on my v-10 the cost is $1.23 for 15 minutes.
Tom N wrote:
Yes, I mean Watts. But, my point is your generator will charge batteries much faster than a solar setup. An you already own it.