Can't run dual alternators? Boats do it all the time. Lots of big sailboats have 2 110 amp alternators. The key is having one alternator's regulator set at a slightly lower voltage. That way one alternator assists the other until the voltage reaches the other's setting, at which point the first one stops charging. If they are both roughly the same, the regulators tend to surge as one senses a voltage fluctuation at a different time from the other. There are no phase problems because the alternator's output has been rectified to DC.

Am I missing something?

Another way is to use an isolator (diode) for one of the alternators - but since the diode drops about .6 volts, you'd need to adjust the regulator for the loss. Or you could have a dedicated battery and alternator just for "house" needs. My boat has an alternator and a wind generator (small alternator), both wired directly to the main battery bank and they get along fine. If you decide on a 2 battery bank system, get a battery switch so you can toggle between them in case one fails. Check marine stores.


Also, a 100 amp alternator produces 1400 watts (14 volts x 100 amps). There are 746 watts in 1 HP so a 100 amp alternator would theoretically require 1400/746 = 1.88. Add energy losses such as drive belt and pulley friction and add a 100% fudge factor to be safe. This means a 100 amp alternator would require 3.76 hp. It's highly unlikely you'd run an alternator at full capacity anyway, so it's probably less.

Good luck with your hi-tech/lo-tech project!

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer