Need a circuit...or a product....help?

[yaknowthatguy]

Alright gang, I have an idea what I'm looking for, but have had no luck in finding one. I think they exist....but no dice so far.

I have a Pinzgauer 712, so it's 24volt. I am restoring the truck, and plan to run a few 12v items on it - specifically the stereo, and the ham radio (yaesu FT857D).

What I'm looking for is a 24-12v stepdown converter that will run these (I wont run the Yaesu at max power), BUT that has either a small battery for memory preservation on the radios, or that I can combine with a small battery and a charging circuit. I've heard of converters that do this, but can't find one. My pinz will sometimes sit for a few weeks, so a converter wired battery direct is a bad idea... plus the truck has a master switch anyway, and I'd rather not bypass it.

If someone has a good plan for this, or can suggest a specific product, I'd love to hear about it. I can follow a schematic and make something, I just don't have the skills to write one up for this - and dont know where to find an off the shelf converter that would do this.

Many thanks in advance.

yaknowthatguy
fort collins, colorado

 

[Tennmogger]

Might I suggest you spend a little more and get a 24 to 12 converter than you will never worry about. I use several Wilmore converters. These are industrial quality, used on fire apparatus, railroads, heavy equipment, etc, and USA made!

The installation in my U-1300 'mog sounds like what you want to accomplish: nominal 24v from the truck system, regulated 13.8 v out of the Wilmore converter paralleled with a 12 v battery (a big 110 AH because it's also the camper house battery).

In your case, the battery could be a small one. Just let the Wilmore converter supply all the big 'umph' current. I run an FT-857, too.

The converter I use has a control line that can be slaved to the ignition key (off when key is off). Having the 'remote enable' circuit in the converter is a handy touch. The model I use is an older one, a 1416-35 (35 amp), and obsolete. I'd suggest looking at the models available at http://www.wilmoreelectronics.com/ to help you decide. I also use their model 1416-15, and a model 1640. As you can tell, I really like Wilmore. I got tired of failures of Samlex and other such imported china junk.

BTW, I found that a distribution box based on Anderson Powerpole connectors (like the West Mountain Radio RigRunner series) makes a great way to patch all this together. Install Powerpoles on your radios, one to the 12v battery, one on the 12v output of the converter, then just plug them in as desired, with appropriate fuse in the Rigrunner slots. If you get a Rigrunner with a switch on part of the strip you can completely turn off the loads if you are going to let the rig sit for a while.

The distribution panel concept really helps troubleshoot in case of problems.

Hope that helps,

Bob WB4ETT

 

[dwh]

http://www.google.com/search?q=dc-d...s=org.mozilla:en-US:official&client=firefox-a

 

[Gooseberry]

OK I never worked on a 24v system but does it not still use 2 12 volt batteries in series? If so could you not just tap off the first one from ground?

 

[Tennmogger]

OK I never worked on a 24v system but does it not still use 2 12 volt batteries in series? If so could you not just tap off the first one from ground?

Sure, there's be 12 v across the 'lower' battery. The problem is that the load on the two batteries would be different, and charging would be asymmetrical. The lower battery will eventually undercharge and the upper battery overcharge. There are charge equalizers available to compensate, but those are another expense.

 

[Gooseberry]

Sure, there's be 12 v across the 'lower' battery. The problem is that the load on the two batteries would be different, and charging would be asymmetrical. The lower battery will eventually undercharge and the upper battery overcharge. There are charge equalizers available to compensate, but those are another expense.

Thank you makes sense

 

[taugust]

Not sure about your stereo setup, but the 857D (I believe) uses non-volatile memory, so once programmed, does not require power to maintain memory. I have unplugged all my mobile ham radios often with no loss of memory. Hope this helps.

 

[yaknowthatguy]

now that's a good point, and I will admit to not having used my radio lots for a while, so I dont recall the memory status on the 857. The stereo will be a Fusion IP600 - mostly so I can tuck the iphone inside safely and use it for music. the times I need radio I can listen to a couple of stations that are no big deal to reprogram.

This gives me food for thought, and may well reduce the overall cost of my planned build. thanks for the tip!

 

[rezdiver]

i think for your situation your best bet is a battery equalizer. i am using a Surepower 40 amp battery equalizer on my military Iltis. it balances the power between the two batteries so that the truck charges at 24 volts evenly and when i pull 12 volts off the 2nd battery, the equalizer is always working to keep things balanced.

you can use the same equalizer and wire it as a 24-12v converter if you want to run a third battery dedicated to 12 volts and memory situations. i run radios, winch and some other auxilary 12v equipment from time to time. mine is set up as an equalizer and i just draw off my second battery. this way there is no need for a third battery.

this has worked great for me for a couple of years now and the sure power unit is very bullet proof.