2nd alternator, 12V

[m35a2cowner]

Sorry if this is a little bit off topic, but has anyone thought of mounting a 12 volt alternator under the cab to be driven off of the intermediate drive shaft between the transmission and the transfer case. It would charge while the truck is moving and if you needed power and no movement you could put the transmission in gear and the transfer case in neutral and turn the alternator. More room, less vibration, less in the way when doing maintenance. They make self exciting kits for delco alternators, one wire to the battery. I have one on my rail-car (20 HP Wisconsin motor) and it works like a champ. I got it from a small shop that repairs alternators and starters. I have seen one of these self exciting alternators attached to an old chain saw bar and used as a portable battery charger. Just a thought from outside the toolbox.

 

[jesusgatos]

If I was going to mount anything under the cab, it would be a larger, PTO-driven generator.

 

[Lieutenant Dan]

A few questions here what is the relay setup for?

If I add the 12v alternator which I plan on doing can I use the vehicle ground for the 12v system? Wouldn't that interfere with the 24 system?

 

[doghead]

Yes, and no.

 

[joshs1ofakindxj]

My beautiful wiring diagram is attached. The relays let the 12V system come alive and turn off with the 24V system automatically, or work from an accessory switch. So when I get in my truck, I hit the main power switch and the deuce fires up, the 12V radio and CB turns on, etc. No extra flipping of switches and such. Also the 12V and 24V systems can share the same vehicle ground.

 

[swbradley1]

I saw this thread popup and it dawned on me how to keep from burning up those little alternators in the truck, add an inline 50 amp fuse. Doh!!

 

[Lieutenant Dan]

That's what I was figuring the relays where for. That's a good idea. I'm going to be putting a keyed ignition switch in the truck instead of the push button starter switch so I can use the acc side of the switch to power the relay for the 12v system. I'm going to be using a Ford 3g alternator out of a Ford Taurus. I can get them for $15 from the local u pull It and they are 130 amps from the factory. They are also a 3 wire design so they charge better then a 1 wire cause it senses the voltage drop and ups the alternator output.

 

[doghead]

A keyed ignition switch, won't you still be switching 24 volts? If so, the acc terminal will have 24V. You'll still need a relay.

 

[Lieutenant Dan]

Isn't that the point?

 

[doghead]

switch to power the relay for the 12V system

Sorry, I missed the comment that I highlighted in red.

 

[Lieutenant Dan]

Ok so I quick drew this on my note 3. Now of course the 24v signal wire would come from the old push button starter and go into the battery terminal on the ignition switch. From there I would run the 24v signal to the relay from the accessory side eliminating the need for the 12v override relay. I'm thinking about using a 100 amp continuous solenoid instead of a relay so I can have complete control over the 12v circuits cutting everything once the key is pulled. The only thing that wouldn't get cut would be the main power wires from my light bar cause that is controlled by a external control box.

What do you guys think?

 

[SP5]

This may, or may no be apropos of the electrical hook-ups. During the recent restoration of a '61, 55ft Chris Craft yacht, I used oil pressure switches on the main engines, so that when the engines were not running, (no oil pressure), the field curcuits to the alternators were not energized, so that if the key(s) were left on the batterys would not go dead.
Talk about wiring, this boat uses eight( 8 volt batts, and four(4) 6 volt batts. There is two 32 volt curcuits, a 24 volt curcuit, and a 12 volt curcuit, each engine drives a 32 volt alternator, with an additional 12 volt alternator on one of the engines.
Plus there is an inverter, and two seperate chargers, things are a bit complex, but all works just fine,, the grounds are all common, no problem.

 

[brianp454]

Nice thread. My batteries are ~6-7 years old and don't have enough to turn the engine over in the cold now. So, I'm looking for a setup and appreciate the help from folks here. There's a case for having 3 batteries with 2 in the stock system and 1 charged by a Delcotron (my dad worked for Delco back in the day) to be used for typical auxiliary stuff or as a backup. I plan to measure out the battery box tomorrow and look into options.

 

[joshuaz223]

Lt Dan instead of a solenoid I would use a solid state relay far less current draw and very reliable. another thing I would try is the glow plug relay off a diesel truck very high current capacity and low amp draw.


Roy

 

[joshs1ofakindxj]

I used oil pressure switches on the main engines, so that when the engines were not running, (no oil pressure), the field curcuits to the alternators were not energized, so that if the key(s) were left on the batterys would not go dead.

^This

Lt Dan, that is the first issue I see with your schematic, you will constantly be energizing the alternator field and killing your 12V battery. I highly encourage you to copy my schematic in post 125 of this thread. I'm not sure what you're trying to accomplish different from my system? My 12V system comes on with keyed ignition switch I have installed in place of the truck's 24V main power switch thanks to the 24V relay and I also have the over ride switch on the dash to use the 12V system with the main power switch off. I guess I could of just used the ACC position on the ignition switch but I prefer to take the keys out of the truck and with me at car shows where I leave the stereo on for hours.

 

[Lieutenant Dan]

Nothing my schematic is the same as yours for the exception I messed up where the signal wire should have went. It should go to the switch on the key.

The other thing is I don't want to take out the master switch from the 24v circuit. I'm not going to leave the truck on for any reason unless the motor isn't running.

Also technically the field wire should go to the switch and the signal wire should run to the battery so the alternator can sense the exact draw on the battery's not the little jumper to the post on the alternator that senses the output of the alternator not the draw off the battery. Then the alternator doesn't work correctly raising and lowering the output.

 

[joshs1ofakindxj]

The other thing is I don't want to take out the master switch from the 24v circuit. I'm not going to leave the truck on for any reason unless the motor isn't running.

Also technically the field wire should go to the switch and the signal wire should run to the battery so the alternator can sense the exact draw on the battery's not the little jumper to the post on the alternator that senses the output of the alternator not the draw off the battery. Then the alternator doesn't work correctly raising and lowering the output.

I did not eliminate the master switch. I replaced it with a keyed ignition switch, to be clear. I agree on the 3 wire alternator wiring. I have a 2 wire alternator, so that doesn't apply to me.

 

[Lieutenant Dan]

Here's the right way the alternator should be wire.... really not a 1 wire at all..... it can just be setup that way.

 

[Lieutenant Dan]

Oh got ya. I just want to replace the push button switch with a key switch.

 

[yagenrok636]

I wanna get one of these dual alternator brackets! Has anybody heard from Tm America in a while?