Ray addresses a reader in this week’s column (Car Talk home page) wondering if they should upgrade from 6 to an 8 volt battery? Reader is having problems w/slow cranking on his old (1940s) 6 volt equipped car. Ray suggests best course is to revert all electrics to 12 volts, bulbs, alternator, starter motor, etc. I’m wondering why go to all that trouble? The car was designed to run on 6 volts, so why not just install a replacement 6 volt battery. If alternator or starter motor stop working, just install a replacement 6 volt version for those parts too. Seems a much simpler solution. What’s the motivation to switch to all 12 volt? Replacement parts very expensive and/or impossible to find?
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Many vintage cars get switched to 12 volts. Much wider selection of batteries, easy availability of lightbulbs, brighter tail, signal and headlights, more reliable starting. The higher voltage spins an early 6 volt starter faster so it is easier to fire off an old engine. At double the voltage, but 1/2 the current, the old wiring becomes a bit more reliable. Gauges won’t work with the higher voltage so a drop down resistor is needed but those are readily available.
If you MUST keep the 6 volt system, there are shops that are installing LED conversions for the bulbs to drop the current draw and brighten the light.
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Ray had a minor mistake - he said some wiring might need to be replaced. In fact the wires in a 6V car are as thick or thicker than in a 12 V, they need to handle twice the current to yield the same power (P=VI). So, say, the starter cable has to be thicker to provide the same power to the starter in a 6V system (it takes the same power to turn over the engine, 6V or 12V).
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Yes, I was wondering about that as well. I was thinking however the reason for a new wiring harness is a practical one, connector compatibility, more than the wire gauge.
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George, if you think back to the cars of the '50’s, they cranked verrrry slowly, and one of the best imorovements you can make if you want such a car to be a reliable “driver” is to make the switch to 12 volts. There were things we tolerated in the '50’s that would not be acceptable today, such as slow starting, no starting, gear shifting, changing points and plugs every 10,000 miles, etc. Ad infinitum.
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I’ve never owned or driven a 1940’s 50’s car with 6 volt system, but my parents & other relatives owned them, and don’t recall any problems getting them started. I’m guessing they had lower compression ratios than today’s cars, so starter motor not taxed as much. Not saying there were no problems with those cars. Nearly impossible to get the air/fuel mixture correct, so lots of backfiring, fuel odors, hesitations. And of course more-frequent routine maintenance needed for older cars.On + side, pretty easy job to do, and parts for this diy’er work very easy to get. Even into the 1970s, diy’er maintenance for for my truck, plastic-wrapped packages galore on the store shelves of spark plug sets, points, ign rotors, dist caps, even headlights, at most any department store for a few $$$ , K-Mart, Walgreens, Sears & the like. Stuff like that, for common big-seller cars, no need to visit an auto parts store. I don’t find manually rolling up the windows or shifting the gears much of a burden myself, but one aspect of newer cars I think most cars buyer wouldn’t do without, the newer safety features. 40 and 50 cars didn’t even come equipped with seatbelts in most cases. New vs old, it’s a compromise
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Something else to consider, most if not all 6V systems were positive ground.
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Half a day of labor, why go through all that trouble? Much better engine cranking and brighter headlights and 12 volt batteries are available at many stores. How much time did you spend replacing the headlight switch in your Corolla?
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I had a professor in college, an electronics class. He said if you have a 12 volt VW (Beetle) you could put a 6 V starter (from an earlier year) on it and you’d get quicker starting. He said the starter is only used a second or 3 so it doesn’t have time to overheat!
I did own a Beetle but never tried this!
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Does anyone have experience with putting an 8V battery in place of the 6V one, with no other changes (the original question to Ray)? I’ve heard of doing that, but no idea how well it works.
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My neighbor put an eight volt battery in his Massey Ferguson tractor to make it turn over faster and it seemed to work.
I jumped my 1950 Chevrolet pickup with six volt battery from my lawn tractor that had a 12 volt battery and it didn’t do any harm.
The truck would start easily on its own in zero degree weather. I had a problem that the headlights were left on. This happened a couple of times.
I thought I was careful not to do that and I hadn’t been driving the truck at night. I finally got to the root of the problem. I looked out the window of my house and saw the front wheels moving back and forth. I went out to investigate and found a 5 year old kid from the addition down the street “driving” the truck. He was also working the knobs on the dashboard.
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You really do not understand Ohms Law. I=E/R. The load is a fixed resistance so if you double the voltage, you double the current. There are differences between a 6V starter and a 12V starter that gives the 12V starter a little more impedance to drop the current needed.
You pump 12V to a 6V starter, you will fry the wires over time, but the motor will spin faster until it burns up.
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I understand it perfectly. I was comparing the situation of a 6V battery and a 6V starter to a 12V battery and a 12V starter, not the one you describe. In my case both starters take approximately the same power to turn the engine over, so the 12V cable has to carry 1/2 the current.
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@texases, Sorry, I got wound up with all the posts about using a 12V battery on a 6V starter, but Ray did say to replace the starter. I probably should have addressed this to @Mustangman
His post was right above yours.
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Was it because of going to 12v or because the wires were very old and brittle?
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He didn’t go into detail.
I grew up in Up State New York State where the word “Cold” has a couple of extra "o"s… because it’t sooo Coooold in the Winter time…
I had a bud that drove an old fifties something Plymouth that had a 6-Volt system. He strapped in a 12-Volt battery in front of his radiator, behind the Grill, and if he had problems starting his car in the winter, he only had to pull the jumper cables out of his trunk… I think he said he put the 12-volt battery on charge about once a month or so to keep it charged.
My experience with 6vt. cars ('50 Pontiac, "60 VW) is 6vt. systems cranked slower, especially in cold weather. Part of the problem might have been batteries, which were physically about the same size as a 12vt. but had to deliver twice the current to make the same power (this isn’t exactly true, having physically larger individual cells they might have had lower internal resistance…). In any event, 12vt. cars tended to start better when cold and it also seemed that their headlights were brighter, possibly partly due to lower voltage drop at socket contacts, etc. This might be one reason the industry converted, but I suspect another is this allowed a reduction in the amount of copper ($$$) required.
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Likely the case. In general electric motors designed for higher operating voltages usually less expensive. Electric motors with fewer armature contacts are less expensive too. Could be the lower voltage starter motors required more contacts as well. More contacts, those designs usually spin slower. Fewer contracts, spin faster. My Corolla’s starter motor has fewer armature contacts than others probably, so spins faster, compensated by using a gear reduction method. Ray said on podcast his theory is that this is the reason Corolla starter motors of early 90’s tended to be problematic. I can vouch for that … lol …
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I have written much about my first car a 1954 Dodge Meadowbrook. It too had a 6-Volt system, but it also had a “Red Ram” Hemi V8 engine (not the huge hemi, but a “baby hemi,” 241 cu in, rated at 140 HP. It came with a three-speed, column shifter, with a Hydrostatic clutch (Fluid Clutch…) that worked like a torque-converter.
I actually bought this car in 1965, a year before I could get my driver’s license. It belonged to my neighbor and he was selling it because it never started in the winter (we lived in Upstate New York) especially when it got to 20 degrees below…
However, I never had any problem starting that Red Ram on the coldest winter day; after I changed the oil, I used 10w30. I found out a couple of years after I bought it that the mechanic at the local garage that my neighbor took the car to for all his service used straight 30-weight oil in the Dodge, since my neighbor would called him out when he needed a jump and it was one of the mechanic’s ways to pump up his business by “cheating” his customers…
So many decades ago, I know I bought the largest capacity 6-volt battery that fit in the battery holder because my neighbor had that “winter starting problem…”
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