Starter Voltage

Hey all, how do I tell if the system is 12 or 6 volt? I purchased a 47’ CJ2A and the batter was missing. I don’t want to assume it’s 6/12…

thank you!

images
https://imgur.com/a/fgTgz2y

 

A starter will tolerate over-voltage for brief periods, but things like the instruments and lights will not.

My guess is that a 1947 would have been six volt OEM, but may have been modified to 12 volt later. I would pull a light bulb or two, see if they are marked, or try them on 6volts and see how bright they are.

 

What do you have for charging system? Generators and alternators should show the voltage on the tag or pull a bulb and see what it sez.

 

I will dig into the charging system to check it… also sounds like the bulb trick may be the way to check…

 

Looks like it’s a 6v system… Headlights were both 6v.

is there an advantage converting to 12v?

 

I have no problem with original six volt vehicles, kept stock. They work just fine if maintained well.

That said, it slightly complicates adding modern accessories, say a radio or electric winch, or getting a jump start. You will have more choices in 12volt if you intend to make upgrades.

Six volt systems require wiring with gages that can handle twice the amperage of a twelve volt system. Not a big deal in reality, although if you want brighter headlights etc, it is somewhat restrictive.

But I run several six volt vehicles in stock configuration. In some ways it makes replacement parts easier to source, since they are the same as original specification. Customizing is a slippery slope and hard to ever undo.

I suppose it comes down to your personal philosophy - do you want to maintain a original "classic" or are you the type who likes making modifications?

 

I would stay 6 volt, get the best 6V battery I could find, and keep the battery on a battery maintainer. The main complaint I've heard about 6V is slow cranking speed.

 

It sort of depends on one's anticipated use. If it is to be a trail Jeep with an electric winch, absolutely go 12 volts. You can get a 6 volt winch but you would need some really big cable (4-0) to keep it from getting really warm while winching. Not to mention the orders of magnitude more 12 volt winches to chose from.

And as per Pete's post, you can run most 6 volt starters on 12 volts. You just have to limit your cranking time. I have half a dozen old Farmall tractors set up that way.

 

Speaking of cables, your 6V battery cables should be thicker than the generic cables they sell in the parts stores. (The 4/0 cables John aka Duffer mentions are 0000 ga, which is nearly 1/2" in diam. 4 ga that you usually see in cheap parts-store battery cables are about 0.2" diam. 4, 3, 2, 1, 0, 00, 000, 0000)

 

Unless you're trying to to restore it, I would suggesting converting. The modern 10SI (or any modern alternator) will charge at idle (most generators won't), is more reliable, more compatible to modern appliances, is simpler and cleaner (no external regulator) under the hood, and the starter will spin faster, making starting easier.

I've converted a number of vehicles to 12V. Mostly air cooled VW's and my 9N tractor.

I converted a CJ3B to 12V and all I did was swap the bulbs and run a standard cigarette lighter style voltage "dropper" for the gauges. I used the fuel gauge to select the "proper" voltage, selecting each voltage option till it read correctly.

 

I have always converted to 12v for old Jeeps. An alternator charges much better than a generator, especially at slow engine speeds.
-Donny

 

They went 12v for a reason... If it's a correct resto then by all means stay 6v. Otherwise I see no reason not to go 12v. Just my 2c.