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51 Packard with 6 volt positive ground.

Is it possible to make/buy a device that converts 12 volts to 6 volts to use with jumper cables to jump start my Packard from a "regular" 12 volt negative ground car ?

Thanks !

With the size of the transformer you would need to handle the amperage load from a "jumping" operation, It would be much cheaper to just buy a 6/12 Volt battery charger and charge up the battery. Plus it wont put as much load on the generator having to try to recharge a dead battery. Just my

You can cheat and just hook up the neg jumper from the donor car to the starter side of the solenoid of the Packard and then just touch the pos jumper to any ground on the Packard. You would be acting as the solenoid and not putting 12V through your system. This would be for an emergency only.

Jumping a 6-volt car from a 12-volt source is commonly done and has been for decades, not a problem as long as some precautions are taken. 1st, forget polarity of the two cars, always jump positive to positive and negative to negative. As Phil points out, if both cars have the same polarity you can use a single cable between the hot posts and touch bumpers to make the ground connection.

Secondly, don't leave the cables connected for any more than is absolutely necessary, certainly no longer than 5 or 10 seconds at a time, at the most. If you're using 12-volt jumper cables they will get hot VERY fast and perhaps burn any plastic grips or insulators on them if you leave the connection intact any longer than that.

PS - wear safety glasses at an absolute minimum, full face shield and rubber gloves highly recommended. And I'd have a bucket of water handy; though uncommon, batteries do occasionally explode and the electrolyte in wet-cell batteries is approx. 20% sulfuric acid. And others may have alternative advice or actual experience, but I wouldn't jump a gel battery (Optima or similar) unless you could confirm with the maker that it's acceptable to do, whether from the same voltage or not.

I as well as many others have routinely jumped 6v vehicles with 12v vehicles. The best way is to have an accomplice engage the starter BEFORE u touch the cable to the 6v battery. This creates a rather strong drain on the entire connected system so that small bulbs and so-forth will not burn out. However, i've done it by simply connecting and then engaging starter working by myself.
As Owen states above it is very important to NOT leave the jumper cables attached for more than 5 or 10 seconds and follow his safety advice too..

Do not have the 12v vehicle running. Turn key of 12v vehicle to OFF.

I've never tried touching bumpers and ONE cable. My only fear of that would be possible arcing. When arc WELDING on an engine one must be careful not to ground thru the rest of the engine.
For example: do not ground to the end of the crank shaft unless the crank shaft itself is being welded. Arcing could occur then thru the bearings if welding on say an AC bracket.

Some, but not all cars, have an engine to frame ground strap. 55 and 56 Packards do NOT have such a strap. So touching bumpers would make me worry about any ground arcing that mite occur back thru engine components.

Owen Dyneto and Packard V8 nailed it, as usual. We used to do this all the time in the collection I worked for, (actually, two large collections) with no ill effect.
One bit of electrical information: transformers only work on AC (alternating current), cars are DC (Direct Current). They require the change in cureent direction that AC offers to transfer energy through the transformer core to the secondary coil, which is the output of the transformer.

There are 2 safe methods. First is to take out the 6 volt battery and replace with a 12 volt. Make sure radio, lights etc are turned off. Do not grind and grind the starter, you do not want it to overheat. 5 or 10 seconds OK then let it cool for a minute.

Second method disconnect the live side of the 6 volt (neg in the case of the Packard) clamp the jumper cable on the cable and the other jumper, ground on the motor. This cuts the 6 volt battery out of the circuit and eliminates the problem of overcharging and possible explosion. When the engine is running quickly disconnect the jumper and stick the cable back on the battery, the engine will not stall if you are quick.

Guess I've just been lucky over the past fifty years and I've jumpstarted a hundred 6v cars and trucks with a 12v car and never had a problem.

Above has some good advice. Don't have any lights or accessories turned on. Don't spin it over for more than a few seconds at a time. Use quality jumper cables and go positive to positive, negative to negative.

Bottom line, the 12v will spin the 6v engine so fast, if it doesn't start within a couple of seconds, there is a tuneup problem, not a battery problem.

jack vines