Radio cometh... (1 Viewer)

My 24 volt Toyota radio, with FM crystals starting at 90 Hz and going down has been pulled, and I've got a new Pioneer CD deck en route via eBay.
I suppose it's time I start to design a circuit to power this thing.

I have a 24-12 volt converter ready to go, and there are two items I want to power with 12 volt, the stereo and a CB radio. The converter puts out 10 amps max, so I'm OK in terms of current draw.

He4re's the rub, it's not just as easy as wiring from the old radio power source, because I need a constant source of 12v to keep my radio settings once the igniton is off.

Can anyone describe an easy way of doing this? I will purchase a small 12 volt fuse box and ground bus strip.

Thanks for the help.

Howdy Moose

From exprience I can tell you that any constant draw even if it is milliamps is something to stay away from on a 24V Cruiser in my opinion. I consider it something as part of life and accpet that I have to seek to find radio stations (no memory). I know this doesnt help you, but what your asking is pretty complex solution I think - somebody may chime in here and know otherwise Stone? Crushers?. Here, I value every amp of starting power for cold starts and my converter (not a Solar), if running constantly for 12V source could be trouble after a few days. So I have a master switch on my converter and turn on when needed only - the converter is rated at 24Amps continous, I wnated a pretty good sized one to run Stereo, big amp, CB, and a few 12V accessories. It works great - mount above glovebox on 60 series. Good LucK!

Johnny

You're going to be drawing fairly close to 10A already with both the CB and CD player, especially when the CB is transmitting.

It's simple to run an ignition switched source if you already have a converter. Take out the piece over the climate controls that also holds the cigarette lighter. Behind the cigarette lighter will be two wires, one ground (to the body of the lighter), and one (+) 24v (to the middle of the back of the lighter). Use a wire tap and splice a wire to this (+) 24v lead and run that to the coil of a 24v relay. I suggest a Hella 87426 24v relay with a resistor on the coil pins (86 and 85) to avoid voltage spikes as the relay flips on and off (available from Lordco).

As you have probably guessed, this (+) 24v lead to the cigarette lighter is switched power from the ignition. Run a lead from your 12v fusebox to the source pin on the load side of your relay (pin 30), and then you have a switched (+)12v on pin 87 of your relay. You can then wire the radio power lead that requires an ignition switched source of 12v to pin 87 of your 24v relay, and wire the radio power lead requiring constant (+)12v power for radio memory directly to your 12v fusebox. If you want, you can put a 10A fuse inline with the tap off of the cigarette lighter lead to the coil of your 24v relay...but this is not really necessary as the cigarette lighter is also already fused in your 24v fusebox.

If you want to convert your cigarette lighter into 12v to run accessories, then you can remove the (+) 24v lead from the back of the lighter altogether and just run that to the coil of your 24v relay instead of tapping it. To make it a switched power lighter, you can then also run a lead from pin 87 of your 24v relay to the back of the cigarette lighter replacing the original lead. To make it a constant powered lighter, run a lead directly to your 12v fusebox and put a 10A fuse to it.

10A is not going to get you very far in terms of accessories. Most CD players draw at least 5-10A when the bass kicks in, and a CB radio is going to draw at least that much again. Run a GPS or cell phone charger off of your cigarette lighter at the same time that you're using your radio and CB, and you have gone over your converter's limits already. Using the maximum of 10A almost constantly from your step-down converter will most likely also mean a lot of heat production, shortening its service life. This is why I personally like the Solar Converter from G&S as it has no problems supplying 20A of clean 12v power all day without heating up and running at >96% efficiency.

HTH.

Stone, awesome! If the 24 volt radio was switched 24 volt, could I not just use that to power the relay and leave the 24 volt lighter alone?

I'm concerned now about the draw...I figured with my two puny 3.5 " speakers (for now), I'd be OK, but you raise a good point with the CB on transmit....hmmmm....I guess my $5.00 convertor from eBay's not such a great deal...

Why don't you use a small tractor 12v battery. Your 24->12v converter can be used to charge it and you could draw from the battery 'til it's drained if needed...

Yes, Moose...you could use that too. You should be okay, as long as you don't have too many 12v accessories on at once. Cheers.

3fj40 said:

Why don't you use a small tractor 12v battery. Your 24->12v converter can be used to charge it and you could draw from the battery 'til it's drained if needed...

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Thoughts on this idea anyone? I hadn't thought about it, but it almost sounds too easy?

Not sure how you would regulate the charge to the aux 12v battery, and you have to figure out a way to turn it on and off with ignition...probably with a 24v relay.

Space would be the main thing for me. I don't think there's enough room in the engine compartment for a third battery so it would have to go in the passenger compartment somewhere.

...and it'd be just as expensive as a good converter....you're right Stone, time to bite the bullet.

Well, I'm a bit biased because I use a Solar Converter and I know how well they work...but the above setup with a small 12v battery wouldn't cost as much. You're already ahead of the game by getting such a good deal on your small step down converter.

Stone, regulating the charge to this new battery though, how is this acheived?

Stone ~ diagram

Stone, here's a bitmap of what I think we're discussing...you'll note that I have not completed the negative leads from the converter or the regulator...and that I may have the wrong idea with the negative post of the new battery. Please review and edit using Microsoft Paint or W.H.Y....

That looks about right, Moose. Looks like there are several companies out there that sell voltage regulators, but I'm not very familiar with wiring these types of setup...but I'm sure there are others here who have.

From California:
http://www.hydrogenappliances.com/batteryregulator.html

Similar companies up here should sell them also.

Stone said:

Use a wire tap and splice a wire to this (+) 24v lead and run that to the coil of a 24v relay.
HTH.

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I just hooked up the relay as you suggest and its working great. One note you may want to add to that excellent and helpful post on how to hook up the Hella relay is that you need to hook up a ground wire to the other side of that coil. So its 24v+ to either 85 or 86 and ground to the other... Thanks again for all your helpful posts here.

That's a good point, Zander. It doesn't matter whether you put the ground on pin 85 or 86 in regular relays and relays with resistors on the coil. The only time it really matters is when there is a diode in the coil. In this case, putting it one way will work and not the other way. Cheers.

Stone said:

That's a good point, Zander. It doesn't matter whether you put the ground on pin 85 or 86 in regular relays and relays with resistors on the coil. Cheers.

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Actually what I meant was that your original instructions didnt mention a ground at all, and that you may want to mention it.

what about https://forum.ih8mud.com/showthread.php?t=41771, or one sourced local"ish"

just a thought.

crusty

zander said:

Actually what I meant was that your original instructions didnt mention a ground at all, and that you may want to mention it.

Click to expand...

Oops.

I thought I would post some pics of my Solar Converter install with circuit breaker in case they help anyone:

Thanks for the info, it worked perfect!