FMTV 12v Only Alterantor

[Presnut]

Hey, looking over the TMs and toying with a 12v alternator swap for a 2000 M1088. Couldn't you keep the 24/12 wiring arrangement on the batteries to supply your starter, and put your CTIS, fuel/water separator, air dryer, ether injection system, instrument panel gages, and windshield wipers/washer on a 12-24v DCDC converter? That would allow me to find a high output 12v "civilian" alternator for a quarter of the price compared to a dual voltage 200amp+ alternator AND I could more easily integrate an auto relay that would charge house batteries once the engine ones where full (see Blue Sea Systems Auto Charging Relay for my inspiration). 24v lights could be swapped with lower draw LEDs to run off the converter or, swapped to a 12v bus where as long as the watt draw is half of the OEM lights, you could use the existing wiring to power the 12v ones.

It all seems to good to be true but i cant find anyone else whose done this? Any and all input, concerns and counterpoints are welcome.

 

[coachgeo]

you would need a huge 12v alt ... aka.... like 300-400amp to equal a 150-200amp 24v alternator. Your better off to go to what others are doing and that is a commercial 150-200amp 24v alt and a 24v to 12v converter.

math sucks but then again.... looking at Marketplace... High Output 12v alts. are not as pocket painful as 24v alts. interesting idea.

 

[Ronmar]

Yea the trans is also 24v. pretty straightforward and far simpler to replace the dual volt with a straight 24v alt and use a 24-12 converter(easier more efficient conversion) to provide for the 12v lighting loads. Victron makes a nice 70A one that will fit in the passenger dash and would be plenty for the truck 12v needs.

I have already done the 24-12 converter install to my truck. And a few others have also done or started the 24 only conversion. Still using the dual volt alt but 12v is only connected to the batteries(regulator needs this to operate alt properly). I am only running 24v to the cab, and if the alt craps, I can install a common delco, balmar or leece 24v alt. They are very common and not very expensive in the 100-150A range which is a lot of power. But I expect the original 100A alt to last a good long time driving a properly sized battery bank(100AH)…