24v system, 12v alt, & A/C pump.

[Maingear]

I am starting with a 100% stock truck.
I am trying to charge my two batteries with a 12v alternator in parallel and draw from these batteries in series 24v with the aid of diodes.
Has anyone done this yet?

I was at the pull a part yesterday and picked up a 1992 Nissan pathfinder AC pump, alternator, and bracket. I also took a Sianna rear A/C pack unit and installed the front heater core inside this pack. The heater hoses matched perfectly. I would like to install the pump and 12v alt where the original 24v alt is.

If I am stuck with the original alt, I will mount the pump above the alt. I have seen the power steering pics but no A/C on the original 230 engine.

Thanks,

Justin

[randygar]

It's not possible to do a series/parallel setup with just diodes. You will need some form of switching, such as high-current contactors, and you wouldn't be able to both charge and use electricity at once. Trying to series/parallel the batteries is a bad idea in general.

If it's 100% stock, why not stick with a stock 24V alternator? Mount it or the a/c stuff somewhere else...

If you have to use a civvie alternator, use one with an external regulator, or modify it for external regulation. They'll all put out 24V if you use the proper regulator, even if it's a 12V alternator, although you might want to put a ballast resistor equal to the dc resistance of the field winding in series with the field. If you only have 12V parts, you can hook the 12V regulator across one battery even though the alternator is across both, but the regulation will be poor.

You could also swap in a 24V alternator from a truck, tractor, dozer, or whatever, if it has better mounting shape or such.

Another option would be two 12V alternators, but that's just ugly...

EDIT: or use the stock Jeep air conditioning... take the top off and fold the windshield down!

--Randy

[redneck1]

Convert to 12v.It ain't hard.have the starter we-wound change the coil and mount an GM alternator in the stock location.Change the bulbs.
Jon has a pic of mounting fab work. Connie broke the camera in Fla.
Redneck1

[randyscycle]

They'll all put out 24V if you use the proper regulator, even if it's a 12V alternator, although you might want to put a ballast resistor equal to the dc resistance of the field winding in series with the field.
--Randy

The best I have ever been able to get out of any 12V alternator is around 16-17 volts full-fielded. Anything like that tends to shorten the life of an alternator considerably due to heat buildup in the windings. Inputting 24 volts into one will probably just speed up the process a bit more.

Were it me, I'd either go with 12 volts across the board, or if you're trying to keep stock but add 12 volt accessories, then use a 24-12V converter.

Is there an issue with your stock 24V alternator? If not, I'd just fab up the bracketry to mount the A/C compressor and fly with the original. Other than space saving I can't really see an advantage to going to a smaller alternator.

[randygar]

Odd; most can put out >100 volts, and full-fielded can run 120 volt lights and universal motors...

--Randy

[randyscycle]

Odd; most can put out >100 volts, and full-fielded can run 120 volt lights and universal motors...

--Randy

That is using an inverter. Not by themselves. At least all the under-hood welders I've seen work that way.

[rboltz]

Odd; most can put out >100 volts, and full-fielded can run 120 volt lights and universal motors...

--Randy

Used to do this all the time. Run drills and lights at remote job sites. In my old chevy, (it was new then) I put a receptacle in the cab with a toggle switch to full field the alternator and a relay to disconnect B+ from the vehicle. Not sure about the newer stuff but the older alternators were tuff.

[randygar]

That is using an inverter. Not by themselves. At least all the under-hood welders I've seen work that way.

I've never seen an under-hood welder with an inverter... ever. Some of the kits to run 120V loads use some passive electronics, but never an inverter. Most alternator welders consist of a contactor to disconnect the output from the vehicle and a switch to run the field full on...

I'm 3000 miles from my garage, so I can't easily perform any tests... not going to risk frying the diodes in the M715! Find a random externally-regulated alternator, spin it at engine speed, and measure the output... it's usually pretty high.

--Randy

[Maingear]

Is there an issue with your stock 24V alternator? If not, I'd just fab up the bracketry to mount the A/C compressor and fly with the original. Other than space saving I can't really see an advantage to going to a smaller alternator.

Stock alt is fine, just large. I am using a 10 inch pipe split in half to go around the outside of the original alternator. It will connect (pivot) at the bottom alternator mount at the block and connect to the upper bracket bolt that joins the piece from the intake manifold & front head bracket. Then I will mount the compressor on top of this pipe, catching the most forward pulley.

I will go with a voltage converter and mount a small 12v batt for the blower motor and A/C clutch. Plenty of room in the batt box.

Getting more motivated as the temp climbs in Memphis.

Thanks for all the input!

Justin

[randyscycle]

I could've sworn the welders I'd looked at were an inverter type and the alternator supplied most of the power, but not all. The inverter acted as a step-up transformer. They must do something to convert back to DC for welding right? Do they rely on the diodes in the alternator for that then? Seems like a lot of load.