Can’t get your 6 volt car to charge the battery? Tried everything? Maybe it’s because the battery cable from the battery to the starter is 50 years old. Just try it.  Even if it has zero resistance. 15 bucks.  And if it’s a new “complete” cable,  not fabbed  outta cable and connectors,  cut off the integral (permanently installed) battery clamp and put a “bolt on” one on. Then put a new crimp on eyelet connector on the starter end. When you strip the insulation for the crimped connector, make  sure you’ve got a lot of exposed wire  for lot’s metal to metal contact with the new connector. Crimp the connector with a big hammer. Just slam it. Some aftermarket (Chinese) battery cables have poor contact, particularly at the starter end. But change both ends of just to make sure. The poorly crimped starter connector on some of these brand new cables can cause starting problems or slow cranking at best.

This problem is very common and overlooked resulting in a complete conversion to 12 volts. Retaining the 6 volt starter will work with the bad cable, and you’ll never know that’s all it was because of the double voltage.

If your cable is fabbed outta cable and connectors, do it again. Don’t forget to crimp the new starter connector with a big hammer and a hard slam. Make sure the battery clamp cable attachment bolts are tight.

If you’ve tried everything and it just won’t work, it’s probably the battery cable.

Assuming your 6 volt battery is dead, start the car with jumpers from a 12 volt battery. Unless you happen to have charged 6 volt battery. Then start if with that. But you need the battery in the vehicle in question to have a battery so low, there’s no way it’ll start the car. But it can’t be junk – it has to be chargeable. Best thing is a new battery that’s real dead.

Leave the cables on just long enough to start the vehicle. And if you jump from another vehicle, makes sure that vehicle’s engine is not running. You don’t want to charge your battery at all. You just want to start the car.

With  car running now, if the cable fixed it, the battery should be charged enough to start the car with the proper starter rpm several times at least after about 15 minutes of idling at about 1500 rpm.

Or give it a push and drive it around for about 5 minutes. If it’s fixed, it’ll start.

Best charging system test for any system – empirical.

And make sure the battery terminals and the inside of the clamps are super clean. The black oxide that forms on them will not conduct electricity. No matter how many generators and voltage regulators you try. And for longevity, reliability and the lowest chance of failure for any reason on  your next trip to Mars,  try to avoid the use of an alternator. Alternators are made of aluminum, including the bearing housings. Aluminum is prone to cracking where the narrow part meets wide diameter part because of the hold down strap holding firmly holding  it on the stand and the belt trying to remove it; working against the strap. Lotta stress at the wide/narrow interface.

Also, the softness of the aluminum makes the bearing housings prone to wallowing out giving the armature the potential to touch the field windings resulting in a no charging. Generators are made of steel and seldom have the wallowing problem and  they never crack. And the Edison technology of the generator is hard to hurt if you connect a battery backwards for a few moments but it can kill a diode in an alternator  instantly leaving you walking.

These cars came new with a 6 volt electrical system and there’s nothing inherently wrong with it or mysterious. There are no “unfixable problems”.