shotty
Active member
- 211
- 56
- 28
- Location
- Northern VA :(
Just a quick thought the other day. It would be nice to have switchable 12/24v where you can parallel the 12v batteries or series them for 24v if you wanted to slave someone or be slaved yourself. It would also be handy if you ever needed to do some emergency welding. The circuit I've attached is done with a couple of motor contactors and has three modes of operation:
1) Main 12v battery isolated from second battery. Should help prolong the lift of the batteries as they aren't trying to charge each other when the truck is off.
2) Parallel the two 12v batteries together by activating the contactor labeled "12v". This allows charging with one alternator, as well as double the current capacity for starting if you choose to keep your 12v starter.
3) Series the two 12v batteries for 24v output by closing the contactor labeled "24v". You could use that to drive a 24v starter while still keeping a single alternator for charging. Older Mac trucks would do this kind of 24v start 12v run setup.
For those that are wondering, if you engage both contactors at once it behaves just as if neither was activated. The secondary battery is isolated, and the primary battery is still connected to the truck, just like always. This is a bit of a safety measure to prevent letting the magic smoke out of your electrical system should something funky happen with the contactors.
I've got an improved version where there is a "24v enabled" relay that closes only when the "12/24v" output is pushing 24 volts to ensure you dont try to turn over your 24v starter when it's set to 12volts. It would PROBABLY just crank really slow, but I don't want to find out
The other thing I added was a third contactor to enable/disable the slave port which is controlled by the 24v enabled relay. This is to prevent someone pushing 24v in to your system when it's configured in 12v mode...
Lastly, I haven't dug too far in, but incorporating this in to the stock CUCV electrical system should be easy peasy. The benefit would be that now you could individually charge each battery with its own alternator. If one of the alternators die, you could STILL charge both batteries by paralleling them when running, and using 24v for starting. Seems like a pretty awesome backup system to me.
It looks like it would be around $200 for the two contactors if you went out and bought what you could find right now. They are on ebay much cheaper used though, and I'm almost positive you could buy a set of reversing contactors and rewire them in to this configuration and save a decent amount of money. Still not cheap though, but if you really want 12 and 24v systems with some flexibility it might be worth it to you like it is for me.
1) Main 12v battery isolated from second battery. Should help prolong the lift of the batteries as they aren't trying to charge each other when the truck is off.
2) Parallel the two 12v batteries together by activating the contactor labeled "12v". This allows charging with one alternator, as well as double the current capacity for starting if you choose to keep your 12v starter.
3) Series the two 12v batteries for 24v output by closing the contactor labeled "24v". You could use that to drive a 24v starter while still keeping a single alternator for charging. Older Mac trucks would do this kind of 24v start 12v run setup.
For those that are wondering, if you engage both contactors at once it behaves just as if neither was activated. The secondary battery is isolated, and the primary battery is still connected to the truck, just like always. This is a bit of a safety measure to prevent letting the magic smoke out of your electrical system should something funky happen with the contactors.
I've got an improved version where there is a "24v enabled" relay that closes only when the "12/24v" output is pushing 24 volts to ensure you dont try to turn over your 24v starter when it's set to 12volts. It would PROBABLY just crank really slow, but I don't want to find out
The other thing I added was a third contactor to enable/disable the slave port which is controlled by the 24v enabled relay. This is to prevent someone pushing 24v in to your system when it's configured in 12v mode...Lastly, I haven't dug too far in, but incorporating this in to the stock CUCV electrical system should be easy peasy. The benefit would be that now you could individually charge each battery with its own alternator. If one of the alternators die, you could STILL charge both batteries by paralleling them when running, and using 24v for starting. Seems like a pretty awesome backup system to me.
It looks like it would be around $200 for the two contactors if you went out and bought what you could find right now. They are on ebay much cheaper used though, and I'm almost positive you could buy a set of reversing contactors and rewire them in to this configuration and save a decent amount of money. Still not cheap though, but if you really want 12 and 24v systems with some flexibility it might be worth it to you like it is for me.
