Waaaaaaay Off Topic Generator Question

We are mounting a diesel generator to a diesel box truck. I am trying to figure out whether we should use the truck's battery or add a separate battery. Will there be an issue if both the truck's and the generator's alternators are trying to charge the same battery?

Thanks

If you use a single battery for charging both generator & truck it may result in a low votage. Hence power outage, to be on the save side I suggest you add a second battery.

I would say yes, there will be a problem.
you have 2 motors generating 12 volts each charging 1 battery. A 12 volt battery cannot be charged with (2) 12 volt power supplies totaling 24 volts at the same time. i could be wrong.

regards,
james

+1 james above - Many trucks have 24v electric systems, many generators have 12v electric systems.
Yes, you could wire the generator into just one battery, but then you'd need to isolate it from the truck and it'd just be dirty/complex (if not unsafe).

If you have a 12v truck, it'd be easier, but just buy a gel-cell (Optima red top or yellow top) for the generator and be done with it.

-John

Thanks for the input guys. I will be using a separate battery.

James Mcquade said:

I would say yes, there will be a problem.
you have 2 motors generating 12 volts each charging 1 battery. A 12 volt battery cannot be charged with (2) 12 volt power supplies totaling 24 volts at the same time. i could be wrong.

regards,
james

Click to expand...

2 12 volt batteries don't necessarily equal a 24 V system. For that to happen, you would have to tie the negative of one system to the positive of the other and then measure across both batteries.

If you tie the negatives together and the positives together (in parallel), then the battery system would only be 12 volts.

The problem with 2 charging systems is that they both won't be exactly the same voltage output, so you wouldn't want to tie them together without some other provision.

There is no reason that you can't just use the truck's alternator to charge the battery and use the same battery for both the truck and the diesel engine (assuming they are both the same voltage).

We have a 40 ft gooseneck portable classroom that we pull with a Duramax.
It has a 3 phase generator with it's own battery pack (2). The truck also has 2 batteries.
They can be connected together much like a camper and we have occasionally needed to charge one from the other.
Definitely use separate batteries but arrange for a disconecctable connection between them. A very nice feature if someone leaves the lights on during a cold winter day you will not have to walk.

I have seen in RV and 4WD camping Magazines that you can get a smart battery charger
eg you run a Dual Battery system (12,24 V whatever) one battery for the vehicle, the other for all the fun stuff (Fridge, Lights, TV etc)
The charger charges the primary battery first then the secondary battery, so you can always start the Vehicle.
You can run the secondary battery totally dead and not effect the primary battery at all. Done with diodes plus other stuff I think.

I believe that a dual charger system is possible.

I would have separate batteries. I would want to always be able to drive the truck somewhere for a service on the generator.

You will be very hard pressed to find ANY truck made in the last half centrury or so that has a 24V system. Those multiple batteries, no matter how many, are parallel wired--not seies.

ASSUMING
1. The truck is 12 V Run AND Start not 12v run 24V start
2. Both batteries truck and gen set have same polarity to ground ie both are for sake of discussion neg grounded.

It is possible to parallel the two batteries and charge with either one or two alternators. You can also parallel the alternators BUT the regulators are not set up for parallel operation.

In this setup I would run the two as completely separate systems. If one battery is dead you can use other to jump start. If one alternator dies you can charge both batteries with only one - after installing jumpers to parallel batteries.

Make darn DOUBLE certain you watch the polarities when paralleling batteries - kinda exiting if you get it wrong.

Dan Bentler

Generators are a big part of my business - not the little ones usually - but the same applies - KEEP THEM SEPARATE - that is both batteries and battery chargers.