Running two alternators on same car?

[j-c-c-62]

Dual Alternator Kits

Those solutions are for seperate 12V systems, and make a lot of sense in those applications, but mine is a single system and must remain so.

 

[Photon440]

Those solutions are for seperate 12V systems, and make a lot of sense in those applications, but mine is a single system and must remain so.

If you have low draw, why not just rely on the engine mounted alternator?

 

[j-c-c-62]

If you have low draw, why not just rely on the engine mounted alternator?

Two fans, electric water pump, EFI, fuel pump, etc

 

[Moparfever65]

In my mind two alternators would be less efficient than one heavy duty alternator. More parasitic drag. The only reason I can see would be either for redundancy in case of failure, or if you can't get one with sufficient amperage.

 

[j-c-c-62]

In my mind two alternators would be less efficient than one heavy duty alternator. More parasitic drag. The only reason I can see would be either for redundancy in case of failure, or if you can't get one with sufficient amperage.

Well, the fans, fuel pump, electric water pump, etc are all in the rear of the car, or maybe less than 4' from where a DS mounted alternator would locate. That load right there may approach 90+A, and running all that from the front is just more downside with a trunk mount battery. Additionally, this split/asymmetrical charging system favors rear and low COG placement for both units. Any additional parasitic drag is an acceptable tradeoff.

 

[Jeff Peterson]

Obviously, my needs are different than the op's, but a plow draws 400+ amps, especially if your trying to "stack" the snow, imagine doing this hundreds of times a day/night, then my setup starts to make sense.

 

[451Mopar]

Question? Where and how is the rear alternator mounted?
I could see having a driveshaft driven alternator on a truck with a 2 part driveshaft driven near the carrier bearing with the alt mounded to the frame.
Having the alt mounted to the axle and driven off the yoke, the alternator mounting will take a pounding from suspension travel, and the wiring will be moving with the suspension, so it would need to be secured with clamps to not pull on the alt output stud. It is also in a lower position where it might get damaged.

 

[j-c-c-62]

Question? Where and how is the rear alternator mounted?
I could see having a driveshaft driven alternator on a truck with a 2 part driveshaft driven near the carrier bearing with the alt mounded to the frame.
Having the alt mounted to the axle and driven off the yoke, the alternator mounting will take a pounding from suspension travel, and the wiring will be moving with the suspension, so it would need to be secured with clamps to not pull on the alt output stud. It is also in a lower position where it might get damaged.

All your concerns all valid and will have to be dealt with. The first car I expect to try this on will be a Magnesium Dana 60 live axle with a 3-point coil over suspension. The Final car if it works will be an IRS set-up, so no direct vibration/road bump issues, as it will be solid mounted. All will seldom be street driven and will run off yoke mounted pulley so no geometry changes as rear moves being alternator is mounted to the rear. I see rain/puddles as my biggest concern. Dirt cars use this solution with a live axle, and I cannot imagine a tougher beating then that application. Of course, they may only last a race or two? The alternator will not be lower than the fuel cell so there is that, but the car will be set to run low.

 

[j-c-c-62]

Obviously, my needs are different than the op's, but a plow draws 400+ amps, especially if your trying to "stack" the snow, imagine doing this hundreds of times a day/night, then my setup starts to make sense.

Not clear, what is drawing that much current in this snowplow application?

 

[451Mopar]

All your concerns all valid and will have to be dealt with. The first car I expect to try this on will be a Magnesium Dana 60 live axle with a 3-point coil over suspension. The Final car if it works will be an IRS set-up, so no direct vibration/road bump issues, as it will be solid mounted. All will seldom be street driven and will run off yoke mounted pulley so no geometry changes as rear moves being alternator is mounted to the rear. I see rain/puddles as my biggest concern. Dirt cars use this solution with a live axle, and I cannot imagine a tougher beating then that application. Of course, they may only last a race or two? The alternator will not be lower than the fuel cell so there is that, but the car will be set to run low.

I was think live axle. IRS makes sense to me. The race cars usually run small light weight alternators, so less mass and could be mounted higher?
You will need to figure the alternator to driveshaft pulley ratio for the speeds you are planning to get the best output from the alternator without over speeding it.

 

[j-c-c-62]

Regarding speeds, the available yoke pulley sizes are rather limited in this application, meaning I'll likely be looking for a rather small alt pulley, which is counterproductive when combined with a high amp alternator. Well the mass has to be somewhere on the car for the amount amps I need, so it might as well be low and at the rear and on the centerline. Unfortunately, it adds to the unsprung mass, but with the Mag Dana 60 I should just be back to my starting point is my thinking. We'll see.

 

[Jeff Peterson]

Not clear, what is drawing that much current in this snowplow application?

The hydraulic pump is powered by an electric motor and your always trying to raise the plow with it loaded with snow to pile it out of the road/lot, and with mine being a power “vee” that’s just more load on the batteries.
I just guessed on the amps, this is from Boss plows website
ONLY 243 amps, but again many times over and over with hardly any recovery time in between.

 

[j-c-c-62]

Wow, that like 4 hp?
Surprised that in your case with a separate alt they did not upgrade to a 24V or higher system

 

[451Mopar]

Regarding speeds, the available yoke pulley sizes are rather limited in this application, meaning I'll likely be looking for a rather small alt pulley, which is counterproductive when combined with a high amp alternator. Well the mass has to be somewhere on the car for the amount amps I need, so it might as well be low and at the rear and on the centerline. Unfortunately, it adds to the unsprung mass, but with the Mag Dana 60 I should just be back to my starting point is my thinking. We'll see.

Post some pics when you get it done. It sounds interesting. Is the drive a cog belt like on an external dry sump pump?
I was just thinking a setup like that might need a clutch or mechanical diode / sprag for when the car stops it will slip the altenator belt trying to stop the alt also.