Charge 12v batt in 24v truck

[mm58]

Hello, hoping some of you electrical gurus can help me out here.

I have a 24v truck, but would like to keep an isolated 12v batt that I use for my fridge topped off with the trucks 24v charging system.

Currently the battery stays topped off with a HF 45 watt solar panel. But with the fridge running, that's only good for about three or four days. The solar can't fully replace what the fridge draws.

I'd like to supplement the solar charge with charge from the alternator when I'm mobile.

Is there a fairly simple and affordable way to do this?

Thanks for any input?

 

[Westech]

A 24-12v converter. There is a member who is selling them. 100 amp chargers.

 

[Westech]

You can get cheap ones all day also.just google 24-12 v converters

 

[andy3]

Be aware that you don't want to drain your starting batteries to run your fridge. What is your design goal? How long do you want to run your fridge? How long between (days) are you going to move your truck?

 

[Warthog]

What type of truck? Many people will add a 12v alternator or a 12v/24v unit

 

[MtnSnow]

Fairly easy to also put in a battery isolator with the 24v/12v converter so the 12v battery gets charged while the motor is running but then the 12v battery becomes isolated from the 24v battery bank so the worst that will happen is the 12v battery gets totally depleted (since the solar can't keep up with the fridge) if the truck isn't started often enough.

 

[mm58]

I do have a 24 to 12v converter to run a few accessories like radios and lights.

So you guys are saying I can hook up a 12v battery to the 12v output of that converter to take a charge? Seems like it would smoke the converter, no?

 

[clinto]

I do have a 24 to 12v converter to run a few accessories like radios and lights.

So you guys are saying I can hook up a 12v battery to the 12v output of that converter to take a charge? Seems like it would smoke the converter, no?

I'd like an answer on this as well. I have 2 trucks, but only one dual voltage output alternator. If you could charge a stand-along 12V battery with a cheap converter, that would be ideal.

I thought anything that charged a battery had to have a variable output-like a voltage regulator.

 

[skinnyR1]

I'd like an answer on this as well. I have 2 trucks, but only one dual voltage output alternator. If you could charge a stand-along 12V battery with a cheap converter, that would be ideal.

I thought anything that charged a battery had to have a variable output-like a voltage regulator.

I am using a Vanner Equalizer to do just that. The equalizer charges the battery for my 12V system. The 12V leg on the equalizer goes to the stand alone 12V battery instead of the middle +/- posts on the two 12v batteries for 24V.

Keep in mind though, that it can't do both. It is either an equalizer, or a charging system.

 

[mm58]

clinto, please tell me more about the dual output alternator. So it has two "taps"? One for 12v and one for 24v? I guess that would also require two separate voltage regulators (?)

 

[clinto]

clinto, please tell me more about the dual output alternator. So it has two "taps"? One for 12v and one for 24v? I guess that would also require two separate voltage regulators (?)

This thread has links to more threads about them. There are 100, 200 and 400 amp units ( I think).


http://www.steelsoldiers.com/showthread.php?t=104921

 

[mm58]

Thanks clinto!

 

[FullSpecial]

Dual output alternators can be pricey and hard to replace. Not to mention big and heavy *HUMMER communication shack models*.
I'm into this about $500 for the 12v side:

 

[mm58]

Well, I think I just need to go back to my original plan to use the stock 24v alternator.

Would I be able to put 24v into a 12v regulator? Or would that cook the regulator?

 

[FullSpecial]

I would think melt would be the word.

 

[mm58]

Gotcha. Just had to ask

 

[LiqTenEXp]

why not run 2 12 volt batteries for this refrigerator? Have the truck charge across them in series and the solar panel hooked up in parallel to them. Then run a DPDT switch or something to select between them as a primary/secondary system. This allows you to keep your trucks alternator config, have 2x the capacity, and only at the cost of a switch and a battery.

The only issue with this setup is you probably want to run a relay that disconnects the charging connection of the batteries when there is no voltage present at Pin A for example of the power/relay box. This way they only charge when the truck power is turned on. They could get drained if you leave the truck on without it running. I would connect pin D of the power/relay box aka wire 568 to the + of the batteries and ground of chassis to their ground. This will isolate them from the truck batteries when there is no power at A. Pin A would engage the relay as described above and the other side of the relay coil would just go to ground.

 

[mm58]

Hmmm, that sounds like a possibility. Actually, the fridge will run on either 12 or 24. So maybe I should do this:
*Get a second battery and connect in series to the other one to have 24v.
*Run the fridge on 24v
*Charge the batteries from the 24v alternator just like the
trucks main batteries.

I wonder if it would even be worth it to keep the solar system. How might I integrate it into charging the 24v?

Thank you LiqTenEXp for the idea

 

[LiqTenEXp]

I just updated it with some more solid details including some wiring info so take a look at it again. I tried to make it so they would only connect when you have the truck running and isolate when not. If the fridge runs on 24V then you just made it simpler and removed the need for the output switch.

I was thinking back to my comment about running the panel in parallel with the batteries. That won't work really but you could at least put it across one of them.

 

[mm58]

I'm confused as to your references to Pin A, Pin D, and wire 568. My truck is a Pinzgauer.