Assistance Needed - electrical question - variable 24v to 12v and back.

[A12ozProphet]

I’ve got a m1009 with the two battery/two alternator setup. I run a inverter for my work but the 12volt side can’t/doesn’t put out enough juice for most of my needs.

So my question is will the following work.

Make my truck variable voltage by building a “switch, see below” that connects the battery's in series “24volt” to start it, starter / glow-plugs etc…” then once its running pull my “switch” to go to a parallel connection. Which would be accomplished by disconnecting the front battery positive from the rear battery neg. and simultaneously connecting pos. to pos. and neg. to neg., so I’d have double the 12volt capacity for the inverter to draw from. Will it work??

 

[rlltide12]

Id say no, and here is why. The entire truck minus the starter and GPs is 12 volts. In a normal setup, the 12 volts is achieved with a wire tapped into the jumper cable between the two batteries in series for the 12+ and the body for a ground. In your diagram, yes, it would work to start the truck then switch to 12 volt feed for the truck. But to make this work, you would have to have the 12 volt + feed wire disconnected during start ups, otherwise you would be feeding components with 24 volts and you do NOT want to do that. With the wire disconnected, this means no start, because the injection pump requires 12 volts to engage the fuel shutoff solenoid. So in short, no this will not work. Best option is to install a third battery and run it in parallel with the front battery.

 

[MakersTeleMark]

Agreed on the third battery. I run my inverter off of a blue top which is charged by a solar panel, and connected via an ACR to the truck.

 

[Skinny]

There are systems out there (usually marine applications) that can solve this problem but its a recipe for disaster and expensive.

Agreed with the 3rd battery setup. What are the specs on the inverter and installation parts? Typically an inverter needs a bit more than just the bare minimum of current flow to operate at peak capacity. You may need to swap out for a 24v inverter to utilize both batts and gens or add a larger alternator on the 12v side to accomodate the inverter draw.