Is it possible?
Are there problems when doing so?
Would they both charge at full capacity if demand required?
I'm thinking a smallish engine driven alternator, 40-50 amps, and a driveshaft driven larger alternator 60-80 amps that connects to trunk mounted battery.
This configuration;on would be appealing to me if they would "get along".

Assuming completely separate systems, then yes, if the same system then I'm not sure your wiring would like it and I cant imagine how it would be beneficial. What is the purpose?

Are planning to run them in parallel or have them support different loads?

They would work just fine if they are both fed the same sense voltage at the regulator.


...but why?

I'm going IRS, so a driveshaft rear mounted Alternator is relatively easy.
Not sure about occasional road splash water
I like my weight low, and rearward.
An engine mounted alternator only needs min output when at rest/idle, when moving and the driveshaft alt is in play, demand is higher and some recharge is likely needed depending on idle time.
Car would see minimum street use vs track car.
Charging systems would be parallel.

System would probably be similar to a boat with twin engines. There is a battery isolator/distributor that both alternators feed into. The battery or batteries are fed from that. Its basically a set of electrical check valves to keep current from going places you don't want it to.

Some new 6.4 Ram trucks run 2 alternators.
Doug

i was just going to say the same thing.
my one buddy has one of those trucks, but i never really looked at how those are wired up, or inquired as to why they were built that way.

If the alternators have identical electrical characteristics then it would work well. But one will hog a little bit more load than the other depending on the characteristics of the alternators. Probably not an issue if you buy identical alternators.

I would need to think about it some, but I believe that running both alternators off of a single voltage regulator would be best although I don't know if the regulator is regulating field voltage or current .

Unless I'm missing something or thinking way wrong, you'd have to idle for a long time to drain the battery enough to matter. Even with the radio, AC and any other accessories a car can run a long time on a fully charged battery. I drove a car for several weeks as a teenager that couldn't afford and alternator by charging the battery every night, it was 25 miles one way to work, then I learned to build alternators.

why on earth? ....not trying to be rude, but... K.I.S.S

Fair enough, but sometimes " better" trumps "simple", but only one way to find out.

Two alternators? How cute. How about twelve? Bass dyno dudes do it all the time, along with service vehicles. There are companies that make kits for all newer American trucks and vans, along with many cars. There are places that will make you custom brackets for dual 260amp alternators. How much power do you need?

Dual Alternator Kits

12 Alternators, 20 Batteries, 6 15"S... Marquis Self's BASS Cutlass FLEXING!!

Why do they alway do this to crapboxes?

I think i agree with the KISS...
One or the other, the diff mount is a good idea if your car in the limits of weight distribution/reduction like FMJ's
Put the money towards one or two lipo batteries and call it done

Why not just one high output alternator?

I have found some Marine regulators (Balmar) that appear to be a solution, ie two engines for one battery, which I think represents my situation, different speeds, etc. They appear to be robust for weather, small. and reasonably lightweight, but being marine slightly costly and hampering bang for buck on the idea.

And I was just going to mention an ancient video of a Ham radio guy that had ~8 alternators set up to drive the radio. When he keyed up, he'd have to hit the nitrous otherwise the load would stall the engine

Best solution.