New 12v Headunit = two voltage reducers? (1 Viewer)

[Domisean]

A quickie question for the pros- installing a 12v headunit into my 24v system will require two voltage reducers-- one for full time power and one for ignition power, correct?

While searching I also came across the mention that the head unit would not maintain its internal memory if using a reducer, is this the case?

I also heard if you 'don't use it' you 'lose it', any veracity to this one?

 

[Behemoth60]

OK I got this one... I just installed a head unit, and big amplifier into my 24V HJ61 last spring.
I used a 24V-12V converter/battery equalizer to feed the amp and the keep batteries equalized while running. My equalizer is controlled by big solenoids to fully cut power to the converter and amp when truck is off... it's all on when key is in accessory position
I tapped directly into 12v battery for head unit power, to keep memory maintained. Draw is very low to maintain memory, and the battery equalizer more than makes up for any off-balance draw when the truck is off.

So, bottom line,
-use a 12/24V equalizer, not just a converter that feeds the head unit. All 24V systems should have a battery equalizer anyway.
-turn off equalizer/converter with solenoids. Mine have residual draw that kills batteries.
-tap diretly into 12V battery for head unit to maintain memory.

 

[Domisean]

Cool, I hadn't read about this option yet. I found a no frills equalizer for $33 that kicks in once it detects a +/- 10mV difference between batteries. Seems like a great solution for the slow trickle required by the internal memory.

Not sure I understand the issue of the solenoids. Without additional shut off solenoids the equalizer will eventually drain the batteries? Which brand did you use? I'm looking at this one-

Amazon.com: ZHC Battery Equalizer 2 × 12V for Lead-acid Batteris Balancer Charger for Gel Flood AGM Lead Acid Battery: Home Audio & Theater

 

[Behemoth60]

I use Vanner Voltmaster 80 amp equalizers. Super reliable and rugged, but have a parasitic draw... will draw down batteries if I don't drive the truck for a few weeks. Solenoids between the 12 & 24 leads and the batteries shut this down this draw.

 

[cruiserpilot]

What I see is Domisean is looking at a 0-5A balancer,
Behemoth is using a 80A balancer
By memory the BJ74 I just got has two of these tucked away, one shows low amp the other high amp. I can get pics by Friday. I am really new to the 24V world, so just asking
Behemoth, do you keep your balancer under the dash or in the engine compartment? The solenoids you use,
they are ignition actuated?

 

[DenDen]

I don't think you should be feeding main power and memory power at the same time. I burned $300 head unit that way. It didn't die right away, took a month or so. I am 90% sure that's what killed it, however it might be just a coincidence.

With my new head unit I installed a cheap relay from ignition to memory wire to keep it OFF and main power ON when driving.

 

[Behemoth60]

Behemoth, do you keep your balancer under the dash or in the engine compartment? The solenoids you use, they are ignition actuated?

I have three of these installed... each in different locations.. they are SIZE LARGE so placement needs to be strategic. I have a 50A unit in my BJ74, directly on top of the batteries... I have side post batteries, and actually use the equalizer as a batter tie down.
In the BJ42, the 80A equalizer fits in the glove box, and it keeps the batteries happy when the monster 12V radiator fan kicks in.
In the HJ61, I have the equalizer installed under the passenger seat, along with the stereo amplifier.

I only have the realys on the HJ61. The BJ42 and BJ74 ALWAYS need a boost to start after sitting for a while. I really should put relays in, I am killing those poor batteries.

In the HJ61, I use two of these cheapo relays from Princess Auto. I wire the activation solenoids in series (as they are both 12V units), one solenoid controls the 12V feed, the other the 24V. They are triggered off the 'Aux' power from the factory power center in the HJ61. I have 50A circuit breakers between these solenoids and the batteries. Hint, since they are only $19, and they are probably crap... carry two spares for when they inevitably fail when you don't want them too! There are quality Cole Hersee units available too, if one was smart...

I have an additional 24V relay that is Aux triggered, but switches battery 12V power to provide Head Unit, sat radio, ham radio power, and then contstant 12V to head unit to maintain memory

Why do I have a 80A equalizer... because I run a third battery, isolated, to run my 2 fridges on 12V power. The 80A equalizer ensures that battery recharges when the truck is running. I also have a 12V 1750W Inverter that is fed by the equalizer... hence the big amperage.

The vanner's are crazy expensive if you try to buy them new... over $1K I think. But, ebay and patience has put 3 of them in my possession for<$150 each.

 

[jblueridge]

I got confused by my Sony units wiring and naming scheme.
The Memory-constantly-on wire was actually the main power also.
The Power wire was really just power for a relay that made the unit come on.

A kind person here told me to check the gauges of these two wires. (Sorry I cant remember who)
Yes, the Memory lead that I had supplied with just a little current was clearly heftier than the red Power lead.
I had to re-think the wiring.

Check the thickness of those wires before soldering.

 

[Domisean]

Behemoth sounds like you have a pretty serious setup there. I don't plan on kitting out the truck to that extent (yet...) and am just looking for some simple tunes.

Jblueridge, good call on the wiring, I'll play a bit with the system to see what my cheapo head unit likes.

 

[jblueridge]

My original 12V memory power came from a thumbnail-size mini 24-12V converter.
When the $67.00 Sony unit tried to draw enough power for the speakers through that little thing, it burned up.