Outer Limits 4x4 Board

I am an auto electrician but have been wondering has anyone made up a cost effective system for a work ute to do 24v volt jumping but still charge both batteries as 12v I can make a system but its going to be a pain in the arse I was hoping someone has had experience in setting up a vehicle to do this thats not to complicated and idiot proof.?

I vaguely recall seeing a diagram for a commercial product which (I think) did something like this.

I can imagine doing it relatively easily with two alternators - but I guess that's not your intention.

Working on the theory that it's the "bottom" battery which will need more charging than the top battery could you develop a monitor for the "top" battery, which detects when the top battery is charged and then "bypasses" any additional charge current while the bottom battery continues charging? Effectively, a large 12V (13.8V) load to sink the energy which would otherwise cook the battery.

Good luck,

Scott

Do I understand this right - it's a 12V ute with a dual battery system but it sometimes gets used to jump start 24V systems?

Jason

Ah ha! This makes a little more sense. If this is what you're doing, my previous post is crap (like lots of them, really...)

It should be simple to put in a switch or two, to leave the batteries in parallel for charging, but put them in series for your 24V jump-starting.

Or am I missing the point again?

Scott

Um sorry I will be more specific I have a 12v vehicle and will be running 2 batteries in the back and I want to run them in paralel for charging and 12v jump starting and in series for 24v jump starting but It has to be full proof so you cant stuff the charging system on the vehicle??

You could do it with a double pole double throw (DPDT) switch or relay. MUST be "break before make" and MUST be capable of carrying full cranking current of your batteries. Note that it only needs to carry the full current - you don't need to make or break the full current.

The common terminals connect to +ve and -ve of your "second" battery. The NC terminals connect to +ve and -ve of your primary battery.
NO terminal of -ve pole connects to +ve of primary battery. NO terminal of +ve pole is your 24V output.

You could build the same circuit with SPDT switches, but it wouldn't be fool proof - switch them in the wrong order and things could get messy. A couple of SPDT relays might be OK, but if one decides to switch a little slowly you could still be in trouble.

What about winch switches/relays?

Scott

If you have room on the motor to mount a second alternator with 24V output, I would just use three batteries - one for 12V jump starting, and a pair for 24V jump starting. It's less likely to stuff up.... if you have room for the alternator, that is.

This type of setup can be done quite easily.

You need to buy a Hella battery master switch and 2 batteries to put in the back of the ute.

They have four positions, so you can select 12v or 24v for jump starting. The other 2 positions are for off and the other is to connect it to the vehicles battery to charge.

Good luck with it