Building a service truck

[Clay]

Hey guys,
So, I opened my own mobile shop about a year ago and it’s finally getting busy enough to justify a dedicated service truck. I’m buying a 5kw constant 15kw surge inverter to power all my tools, and I’m having trouble figuring out the wiring. I need 24v at the inverter, 12v at everything else, and I’d like it to charge from the alternator. This is what I came up with. The 12v positive from the original battery stays at the starter, and it still grounds to the chassis. Add a second wire from the original battery to the second battery in series, making a 24v circuit, then wire both terminals of the second battery to the inverter.

Y’all know I suck at electrical but it makes sense in my head lol. 2 questions:
1. would this work safely? If not, what changes need to be made?
2. How can I make the alternator charge both?

Attachments:

• 3F20FD39-2BF6-4A58-B432-2461A0BAB0C4.jpg

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[Richard Kirshy]

With out knowing exactly how the NEG (-) is wired internally on your inverter.
My first thought is your going to be sending 24V through your entire electrical system.
NOT GOOD!!!
Assuming:
Your planning on using only 2 deep cycle batteries (OPTIMA yellows or equivalents )
Your standard vehicle alternator can only operate on 12V charging.
If this is the case.
You’ll need to be a little creative..

In order to run 24V safely, you’d need to isolate the vehicle electrical system
Using a dual battery switch as shown above
And with relays A & B closed while relay C is open your vehicles alternator will charge both batteries.

When you require 24V
Relays A & B will be switched open isolating the electrical system.
And Relay C ill be closed.

Only issue is that the ECM is powered down at that point unless you install a small 12V battery as a keep alive which only requires 1 additional relay and some wire.

Some other items to consider:
You’ll most likely require a high output alternator in any case.
Depending on usage, you’ll be drawing off both batteries so you’ll need to keep an eye on the voltage and amperage draw, or you’ll be stuck with 2 dead batteries.

I might suggest a 3 battery system where the vehicle battery is only purpose is to start the vehicle.
The other two batteries can be wired and isloated to charge @ 12V and be switched to get you 24V when needed.

Attachments:

• 1224V.png
• 1224V_2017-04-24.png

[Clay]

Thanks for your response! Since posting this, I’ve found a 12v input 5kw/10kw output inverter. Still gonna run dual batteries, definitely gonna look into a high output alternator, but I don’t have to worry about adding a 24v circuit anymore so it’ll be much easier this way. I think lol

[Author]

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