12v Radio in 24v TLC with memory preserved

[Glenn-BJ74]

Well I think this set-up will work. I have the 12v radio supplied by a 24v-12v converter, which is only on when the ignition is on activated by a relay. This eliminates the continuous current draw of the 24v-12v converter, which will kill a battry set if not used as a DD. The problem with this arrangement -- is the radio needs constant power to preserve the radio memory pre-sets, so I lose radio memory each time I shut ignition off -- a major pain.

To solve this problem -- I installed another 'changeover' relay, which is normally 'on' when not energized, which feeds the radio from a 12v single battery tap to keep the radio memory alive when the ignition is off.

When the ignition is on the 12v battery tap is interrupted and the radio draws from the converter. I installed a 10 amp diode to prevent the 12v battery activitating other 12v circuits I have from my 12v fuse panel (others of you may not need this). The result is the radio memory pre-sets are preserved when ignition is off while drawing only 0.13 amps at 12 volts. This is a standrad draw, which should not affect battery life. The momentary switch-over between power supply circuits is not long enough to lose radio memory. So far it works fine.

 

[seapotato]

so...maybe I'm just thick, but is the second ' changeover ' relay, to prevent the
.13 amps from drawing while the engine is on?

sorta seems overkill when you consider the length of time the engine is running vs. not running....cant hurt tho I suppose!

I say this, having hooked up my stereo basically the same way, tho the memory lead is just hooked to the 12v battery.

I swap the batts side to side every once in a while to keep things happy....

cheers,
ryan

 

[Glenn-BJ74]

Yes the changeover relay is to prevent the radio using 12v battey power. The Sony radio I bought did not have a separate wire for the radio memory - it was shared with the power supply input wire.

 

[Stone]

Yes the changeover relay is to prevent the radio using 12v battey power. The Sony radio I bought did not have a separate wire for the radio memory - it was shared with the power supply input wire.

All modern radios come wired that way. The thick yellow wire that supplies power to the unit and is connected directly to +12V also provides the unit constant current to keep the radio memory.

I've had my Solar Converter on continuous step down conversion mode for at least a week straight (sitting, not driving) that supplied my alarm with current as well as my radio for memory, and it hasn't killed my batteries. I've had my system hooked up this way (as per my link on the FAQ section in the diesel tech section, with the mods to allow me to switch back and forth from step-down to load balance) for three years, on the same set of Interstate Workaholic batteries, and they haven't changed in voltage since the day I got them.

In fact, if I were to take a guess, the way you have your system setup having the radio memory draw on the (+) pole of your low-side battery when the ignition is OFF is what will end up killing you battery bank by putting your system out of balance and is what you were trying to avoid by purchasing a 24-12V converter in the first place. The draw might be small, but if you let your vehicle sit for long periods of time, you will see this imbalance eventually kill your batteries, unless you rotate them frequently like Seapotato (but if you like rotating batteries, then why bother spending money on a converter in the first place).

I would take your multimeter and see exactly how much your converter draws with the ignition OFF and the radio drawing a small current for memory. I wouldn't imagine it would be much unless there's something wrong with the converter or the way it's hooked up. Good luck.

https://forum.ih8mud.com/showthread.php?t=30647

https://forum.ih8mud.com/showthread.php?t=33070

 

[seapotato]

ah, I see, my stereo has the separate memory wire....so I can see where it would be more awkward if it didn't.

as to converters, my present one cost ten bucks brand new off ebay, and I actually have been a bit remiss, and havent swapped the batteries in at least 6 months, with no ill effects from the memory draw.
So I don't think swapping the batts a couple times a year is that big of a deal. and probably isnt a bad idea even without weird 12v loads...
I'm still a tad P.O'd about the whole solar converter thing so by comparison I'm pretty happy with my ten buck transformer..
cheers,
ryan

 

[Stone]

ah, I see, my stereo has the separate memory wire....so I can see where it would be more awkward if it didn't.

cheers,
ryan

Exactly. If he hooked up his stereo like yours, his stereo would be drawing its 12V power while it's on from the low-side battery.

While my Solar Converter may have been expensive, my experience with them has been 180* from yours. I have found them to be very efficient, compact and easy to mount, and they have performed as advertised (as long as the both batteries are fresh to start with and the unit is installed per instructions). I readily admit that I have a bias towards them simply because I have had such a great experience with them so far. But I wouldn't say that it's the only converter/load balancer that I have access to. One of the owners of ICT here in Langley; manufacturers of high quality transformers, circuitry, and converters for large corporations and the US military; is a good friend of mine. But at this point, I still like the Solar Converter better for the reasons stated above. To each their own...

 

[Glenn-BJ74]

The Samlex 24v -12v converter draws 0.25 amps with no load.

 

[Greg_B]

The Samlex 24v -12v converter draws 0.25 amps with no load.

Which one? The larger the converter the more it typically draws, even at no load.

The Solar 20 amp load balancer/converter is spec'd at .017amp with no load. The 50 amp converter on the other hand shows .25amps. .25 amp load will draw down the batteries resonably quickly if not driven regularly.

gb

 

[Glenn-BJ74]

The Samlex 20 amp (about $100).

Have you checked to see if the Solar 20 draws 0.017 amp at no load. If so -- then that is the best way to go.