24V to 12V Conversion?

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T

The11thNickel

10 Year 15 Year
Joined
May 12, 2010
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Location
South Surrey, BC, Canada
Hey all,

I purchased a 1981 BJ42 with a 3B engine a while back, and I've been considering converting it to a 12V system, reasons being:

a) Lack of discernable advantages in my position. I have a block heater and don't plan being away from an available power source when the weather is cold. I like the idea of extra power to turn over an engine, but I hardly think 24V is necessary now, as I hardly see newer diesel vehicles running on 24V.

b) Inability to use common accessories. I currently have a 12 amp 24V to 12V step down converter, and it doesn't quite cut it. I bought it assuming I'd only run a couple speakers, but now I've decided I need more juice for my CB radio and possible a sub woofer. (or other things in the future)

Now that I've installed it I can't return it :censor:, (to get one with more amperage), it may almost be worth it to buy a new alternator, starter, etc and put a little extra money and effort in and avoid dealing with any more challenges in the future. I will also have to dig into my winch to bring it down to 12V, which is really the only advantage I'm sad to lose. (As I've read that 24V winches have a little more grunt)

- - - - - - -

Now, I have read the forums discussing the advantages and disadvantages, but for the life of me I cannot find a guide to the conversion process. Has anyone documented this in a BJ42? Would you advise against doing this?

Thanks for reading, :beer:
 
When you finish the conversion you'll have a truck that works exactly as yours does now... but slightly less well. I have a 12V and a 24V 3B and the 24V starter flips it over significantly easier.

Even if all the parts to change to 12V were free I still wouldn't do it.

90% of the time it doesn't make a difference (my 12V truck certainly still starts fine) but then there is that cold morning when I'm on vacation skiing and I'm happy to have every volt I can.
 
24v is good

The 24volt system is a lot more reliable ,the bulbs in lights hold out longer,there is less strain on the wiring and all the contacts .I have seen some very corroded terminals on heavy plant machinery still working fine!
When my need for 12volt is big enough I will add an alternator and battery ,I dont have a AC pump so I have space for it.

my 2c!
 
run a third battery and directly tap your 12v accessories off of that. Charge the battery through your converter via a charge controller (solar, marine etc). This way you can draw whatever large amperage you want directly from the battery, and charge it through the vehicles charging system within the capacity of your converter.
 
iron_giant said:
run a third battery and directly tap your 12v accessories off of that. Charge the battery through your converter via a charge controller (solar, marine etc). This way you can draw whatever large amperage you want directly from the battery, and charge it through the vehicles charging system within the capacity of your converter.
Click to expand...

I have thought of this, and even have an extra battery sitting around, but the converter supplies 12A max. If I draw more than 12A from the battery, than it won't be charged by enough power to keep up with the demand. (Probably looking at around 20A of draw, amounting to a single subwoofer powered by a single channel amplifer at 125W RMS, 2 6.5" speakers, an Alpine deck, and sometimes a small CB radio.)

The more I think about it, the more I think a second alternator seems like a good idea. Is this a difficult undertaking?
 
Keep in mind, it'll be a LOT more than just the starter and alternator. every bulb, relay, motor (wiper, edic) and horn and such, needs to be swapped. It would be cheaper to just buy a 12v rig that is in bad disrepair and swap that way than to try to collect the parts.

You should contact AmericanPsycho in switzerland as he was doing the 24v to 12v swap. Last I heard he had purchased a 70 series and is selling his 42.. Not sure if he finished the conversion but he would be a great resource if you are serious about the swap.

Now for my .02. I love the 24v. As said above, it is a much gentler and reliable system when done correctly. I am in the process of rebuilding a 3B and am going to mount a 12v alt and run a seperate circuit for all of my 12v stuff. Amaurer posted a link to a 30amp 24 to 12 converter for $100 on a recent thread about cigarette lighter power. You could buy that and run two circuits with your current converter and have plenty of power for all of your accessories.

Oh, and before you ask, I am doing the alt because I want to leave my wiring stock and I also have a free 12v alt from a 2F. Much less expensive! ;-) If I didn't have it, I would do a converter. For $100, I might buy one anyway as a backup!
 
BreckenridgeCruiser said:
Keep in mind, it'll be a LOT more than just the starter and alternator. every bulb, relay, motor (wiper, edic) and horn and such, needs to be swapped. It would be cheaper to just buy a 12v rig that is in bad disrepair and swap that way than to try to collect the parts.

You should contact AmericanPsycho in switzerland as he was doing the 24v to 12v swap. Last I heard he had purchased a 70 series and is selling his 42.. Not sure if he finished the conversion but he would be a great resource if you are serious about the swap.

Now for my .02. I love the 24v. As said above, it is a much gentler and reliable system when done correctly. I am in the process of rebuilding a 3B and am going to mount a 12v alt and run a seperate circuit for all of my 12v stuff. Amaurer posted a link to a 30amp 24 to 12 converter for $100 on a recent thread about cigarette lighter power. You could buy that and run two circuits with your current converter and have plenty of power for all of your accessories.

Oh, and before you ask, I am doing the alt because I want to leave my wiring stock and I also have a free 12v alt from a 2F. Much less expensive! ;-) If I didn't have it, I would do a converter. For $100, I might buy one anyway as a backup!
Click to expand...

agreed, 24V is just way better when in cold climates and also its much gentler to wiring and such... Only downside is that when you run your batteries dry you cant get a jump from most cars (since their 12V) but since every decent cruiserist should carry couple tow lines with them always tow-start is an option on those cases...
 
Jump starting is not something I worry about. That's BCAA's (CAA or AAA for others) problem. :) One thing to think about, a push start at -15C is usually not too effective with some juice for glow plugs or glow screen. Best solution is to reduce the likelihood of being caught with dead batteries.
 
I have that dual battery vehicles generally only lose voltage on one battery, and that you can just carry a multimeter to determine which. Once you've found whichever battery is low, another vehicle can charge it for a little while, and that can get you on your way.
 
BreckenridgeCruiser said:
Oh, and before you ask, I am doing the alt because I want to leave my wiring stock and I also have a free 12v alt from a 2F. Much less expensive! ;-) If I didn't have it, I would do a converter. For $100, I might buy one anyway as a backup!
Click to expand...

Is there a guide anywhere on installing the secondary alternator for 12V? I figure you need a mounting plate of some variety, a larger belt, and a wiring harness to connect it to a third battery. (Although I have no idea where I can put another battery)

I've decided I like my 24V winch too much, and I figure I should leave it as 24V, as in the future this may be selling point. 2nd alternator it is!
 
You'll probably find a few posts if you do a search - each varuies depending on engine. The ones I have seen usually occupy a free spot, or are in place of the AC compressor or are done with and adapter to run it along side the 24V alternator. I have seen all three on the TD4.2. Either way, you will have to get one longer drive belt.
 
I don't have AC or PS so I have a ton of room to bolt on the alt. I will actually have a dedicated belt for my new alt, evetually, I may put in PS and that will still be good.

O, and I am running a 2B currently, but rebuilding and dropping in a 3B.
 
I was scoping my truck out today, and it looks like I can put the second alternator just under my main one. I'll just need a longer belt and a mounting bracket. Hopefully I can just use the tensioner on the main alternator to set the tightness.
 
If you install a 12v alternator I'm pretty sure you will also need a 12v battery to create a steady 13.8V. With just an alternator the voltage will surge up and down as engine speed increases/decreases.

I have a 24V-12V convertor from Solar Converters in my HJ60, rated for 20A. That works just fine without an auxiliary battery, although I plan to install an aux 12v battery so my radio memory works. I'm getting sick of resetting my station presets every time I start up!
 
Stereo in a 3B BJ42, why bother?

The11thNickel said:
(Probably looking at around 20A of draw, amounting to a single subwoofer powered by a single channel amplifer at 125W RMS, 2 6.5" speakers, an Alpine deck, and sometimes a small CB radio.)
Click to expand...

Have you ever listened to a stereo in a 3B powered BJ42 at highway speed? Not worth it in my opinion, unless you want to go deaf. Save the fancy stereo for a vehicle with carpet and sound deadening, just my $0.02 :cheers:
 
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