Dual Alternator Build-up

[ColoCruiserJeff]

Alright....I've been reading about this for quite some time and I'm getting to the point in my build-up for the motor and front-side setup.

This truck isn't a crawler....but she'll get plenty of play in the high-country. Winch (front and rear) are in the planning...and a good amount of aux lighting.

When it comes down to it....I figure why not do a dual-alternator setup?

I've got a 2F with a high-mount alternator....along with an older F motor's lower driver side alternator mount.

I've got 4 alternators sitting around the shop to play with....so I figured why not?

I've got the 2F waterpump with the double-belted pulley top and on the crank as well.

I'll shoot some pics tomorrow afternoon of what I've got so far.

Any ideas anyone???

 

[Tobugrynbak]

If you manage to get the belts to run square, and each alternator is charging its own battery I don't see a problem.
Where you'll come unstuck is if you try to hook the outputs of both alternators to the same battery. Because the alternators will not have identical outputs, due to differences in components, age etc, there is the "potential" that one alternator will adversely load the other one and cause both to fail.

It is possible to do it, but it requires isolating/buffering the outputs of both alternators. There is a voltage drop penalty which long tern will shorten the life of your battery.

My "druthers", would be to have two batteries, one for basic vehicle electrics, and one for high demand auxillary power (fridges, camp lights, winches, etc). That way you don't get caught out.

Hope that helps.

 

[Pinion]

With two batteries and a marine grade switch, you can save yourself some time and money by running the single alternator and selecting how you want to use the batteries on an as needed basis.

 

[ColoCruiserJeff]

Thanks for the feedback.

I'm familiar with the marine battery switch. Have one in each of our boats....and they work great.

My reasoning for the double alternator was that....hey I've got 4 sitting in the garage....and they're not worth big $$, so why not put it to use.

They'd be running on seperate fuse blocks...completely separte.

I'll let you guys know more as I continue the surgery on the FJ40

 

[bsmith123]

switching

I don't see why not and you could also have it set up to normally run all the new accessories and also switch over power to the original main circuits in case of a failure then you get can home with every thing functioning normal just wont have all the bells and whistles then

Just fuse the main power just in case the failure was due to a short

This could be done electrically ( switch the ground side of a contactor) or with a manual switch

I would think a contactor with a switched ground would be better than taking power through a big ol distribution switch


A bit of wire with terminals could do the same thing for a trail repair but having it switchable is pretty cool

 

[Shipwreck]

My reasoning for the double alternator was that....hey I've got 4 sitting in the garage....and they're not worth big $$, so why not put it to use.

If you are just looking to put your extra alternators to good use how about utilizing the second alternator as a welder...

I've piggy-backed a second alternator onto my engine that is used as a dedicated welder. It gets used all the time. If my primary alternator dies, the second can be wired up easily to take over charging duties.

 

[robmir]

For the last 10 years I had a dual alternator setup on my FJ-40 with the V8-350 hooked to separate batteries and got tired of servicing the GM alternators.

I am doing a full engine overhauling and throwed away both alternators which were replaced by a single high capacity Denso, which is way better than any other and will add a Surepower battery isolator to feed both batteries.

Before I bought the FZJ-80, I had a 1985 FJ-62 with the 3F engine and managed to install a second Denso located on top of the OEM, with fixed brackets, dual larger belts were fitted and tensioned with the OEM alternator and everything worked fine during the 8 years I owned the Cruiser.

People are starting to do a dual alternator setup on the 80 series after a couple of local manufacturers developed a kit which includes the brackets, the belt, the regulator plug, and a second pulley to be bolted to the water pump which drives the new alternator and of course the kit was designed to fit a OEM Denso alternator.

 

[Czar Mayhem]

Check out my rebuild thread
i am rebuilding a military FJ40, it has two alternators

 

[Czar Mayhem]

You guys see the two alternators?

 

[ducktapeguy]

If you don't really need the output, I'd turn one of them into a welder. Then you'd always have a backup for your stock alternator too if it goes out.

I picked up a monster 140amp Leece Neville from a semi truck, but after getting I realized it wouldn't fit into the engine compartment. It fit perfectly onto the stock air pump bracket, but unfortunately that put the pulley right into the fan blade. Now I'll probably just stick it in a jeep and run some 400W aircraft landing lights on it.

Czar Mayhem,

what kind of alternators are those in your pics?

 

[Czar Mayhem]

what kinda alternators are those

I havent even touched the engine yet other than cleaning it so i dont even know what kind they are. Now that you have said something about them, i will check them out and take some pictures for you. This is an ex military truck so i am not sure what they were running off of them. The alternators are normal small size alternators nothing high out put.

 

[spotcruiser]

I agree with the welding alternator. I carried a Ford alternator around in my parts box for a time, set up as a welder per Pin_Head's thread. I also carried a spare regulator so that it could be mounted as a replacement should the stock alternator fail. Personally, though, I don't see any reason to have a second alternator spinning under the hood all the time and just making my gas mileage that much worse.

If you don't really need the output, I'd turn one of them into a welder. Then you'd always have a backup for your stock alternator too if it goes out.

 

[albee]

Hay Czar, this thread is almost 5 years old.

 

[Czar Mayhem]

Hay Czar, this thread is almost 5 years old.

Meaning i should not post here?