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Thread: Advice needed. Starter rewind from 6 volt to 12 volt

  1. #11
    Quote Originally Posted by Willys59Guy View Post
    Thats a great idea! I like that fix, LarrBeard.
    Just starting on reviving a 1948 Willy's CJ2A. It has been running (and running and running) over the past decades, so shouldn't be too hard. However, it's dead now and I'm starting with electrical. If I used a Walmart 12V battery, that 12V/6V reducer... how do you handle the generator? If that is putting out 6V, how does it charge the battery? If I install a 12V generator, seems like that couldn't be directly connected to coil/distributor, etc.

  2. #12
    Super Moderator bmorgil's Avatar
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    I would leave it stock and restore the 6 volt system or, convert it to 12 volts completely.

    There are reasons for converting to 12 volts. On mine there was little of the 6 volt system left. 12 volt systems are more "modern" as far as batteries etc. 12 volt systems are more forgiving of poor maintenance. 6 volt systems are quite adequate however. Most have their own personal preference. On a CJ2A, there is little to convert as far as bulbs etc. The coil needs to be twelve volts. LarrBeard has a good suggestion below to make it even easier. Use the 12 to 6 volt converter on everything but the starter, horn and the ignition + to the new 12v coil. The horn and the starter won't care about the voltage increase. Otherwise, you will need to change all the bulbs, the coil and, the fuel gauge will need attention.

    If the 6 volt generator is working, there is little reason to convert it "up" to 12 volts. Just get it all in good working order and you are all set. 6 volt systems are fine when well maintained. I cannot think of a "good" way to charge "up" from a 6 volt generator to 12 volts reliably.
    Last edited by bmorgil; 07-09-2019 at 12:11 PM.

  3. #13
    Bmorgil, thanks for the reply. So the 6V generator would just generate 6V into that 12v/6v converter that LarrBeard suggested? Just wondering how the 6V generator would charge the battery back through that 12v/6v converter. AND... if I leave it 6V... where can I get a 6V battery for less than $300? They seem to be really expensive.

  4. #14
    Super Moderator bmorgil's Avatar
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    The 12v/6v converter is used to convert a 12 volt battery and charging system, to work with a 6 volt vehicle.

    To get a 6 volt generator to charge a 12 volt battery, you need to be able to adjust the voltage regulator "up" in voltage. I think LarrBeard has a post on how to adjust voltage regulators. I don't know what regulator you have or, if it is possible to get it to 12 volts. 8 volts maybe. You could put a 12 volt regulator on it. A generator will produce a lot of voltage. Reducing the voltage with a regulator increases the current output. I don't know how much current the generator would produce at 12 volts. It might be enough to keep the battery charged. I have never used a "6 volt" generator at 12 volts. Maybe someone on the forum has done it. I do know it can be a little hard on the generator depending on the amperage demand. If reliability is what you are looking for I am not sure how long the generator would hold up.

    Optima makes a nice gel cell for less than $200. There are a few different brands out there for the same as a similar sized 12 volt.
    Last edited by bmorgil; 07-11-2019 at 07:24 AM.

  5. #15
    Super Moderator LarrBeard's Avatar
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    12-volt to 6-volt Converter

    There has been a bit of discussion about converting a 6-volt system to a 12-volt system. There are two approaches to this conversion.

    In the all out, no expense spared conversion, everything electrical gets changed to 12-volts. If an early 6-volt CJ is the basis for a custom build, this approach is often taken. The 6-volt generator and regulator get swapped for a 12-volt alternator and regulator. The starter gets changed to a 12-volt starter. Bulbs and headlights change to 12-volt, as well as little things like blinker modules and windshield wipers. The most aggravating part is often swapping sensors and gauges and getting them to match.

    Then, there is a less radical approach that is “good-enough”. This involves adding a 12-volt alternator, but keeping the 6-volt starter. It is probably a good idea to change to a 12-volt coil and you would need to change headlights, brake and tail lights, blinker modules and the windshield wiper motor.

    The 12-volt to 6-volt converter that is being discussed is suggested as a way to accommodate the 6-volt sensors and gauges to the upgraded 12-volt system. The gauges and sensors are fairly low current loads. In the 1950’s and 1960’s, many manufacturers used mechanical voltage converters to keep the existing 6-volt gauges when the vehicles went to 12-volt systems. Mechanical regulators are tailored to specific systems and one size does not fit all.

    That is why I suggested a modern three-wire electronic voltage regulator to power the gauges and sensors in the instrument cluster. They will also handle the two or three bulbs that light up the cluster. But, because of their power limitations, these converters will not power the head, tail and brake lights and turn signals. The standard 6-volt converters are not absolutely perfect for this – a 6-volt system usually runs at about 7.2-volts at charge, but “good-enough” is the goal here.

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