explain 12 24v alternator.

[Davebb]

Hi all. Can anyone explain a 12 24v alternator? It's on an 88 superliner. It takes lots of rpm (2100) to start it charging. Is that right? The guy that I'm helping work on it says the truck has 4 12v batteries and that it's supposed to charge two of them at a slow charge rate and the other two at a much higher rate. That doesn't sound right to me. I've looked at the wiring diagram found on this forum under wiki and it seems that the alt has a separate 12v terminal. I wonder if somehow that has a trickle charge designed into it.

The Alt. has a box mounted on the back of it wired to it.

It would be nice to know what the maker of the alt. had in mind.

Can anybody straighten me out on this?

[bubbamobilin]

I'm no expert on the subject but I'll tell ya what I know. The alt is 12 volts but has a transformer on the back that increased the voltage up to 24. 24 volts goes into the two batteries on the right (passenger side) and 12 volts is trickeled down to the two batteries on the left. If you check the voltage with a voltmeter on the batteries on the right you will get a 12 volt reading at the posts, but because of the negative ground system you have to ground straight to the frame and there is where you get 24. When I jump start other equipment with my 1990 Superliner I alway jump start from the right side, one cable on the positive post the other straight to the frame for 24 volts of juice.

[theakerstwo]

The Deco 12/24 has the battiers connected in a configeration of 24 volts and connected to the starter in 24 volt configeration.It is trhen charged by the 24 volt alternator. But the alter has a 12 volt tap on it also only for the 12 volt acc in the cab. Not for charging anything.

[Davebb]

Thank you very much for the answers. I appreciate your time.