by David Grainger
President, The Guild of Automotive Restorers
The twelve volt batteries in our modern cars are one of those items that very rarely concern us. They have become reliable and maintenance free and are often never replaced for as long as a car is owned. Such was not always the case. Originally automobiles had clusters of dry cell batteries linked together to create whatever voltage was required. These were used to provide spark for starting the car, then the vehicle would continue on a magneto. When wet cell batteries which could be recharged became available cars had generators mounted on them and could also employ electric lights rather than acetylene and kerosene, a great improvement as acetylene lights could be dangerous if not operated properly and threw very little light compared to electric arc lights. Each step forward is an improvement on what went before, and only when looking back do we see how troublesome something can be. Early electrical systems were troublesome and unreliable, but they were a vast improvement over what went before. As the technology incorporated into cars improved, more and more items on the car became electrically operated starting with simple luxuries such as interior lights, lit instrument panels and cigar lighters. (Many twenties and early thirties cars had cigar lighters which reeled out on their own electrical cord from the dash and could be passed as far as the back seat.) By the middle of the fifties cars had ranks of electrical switches and knobs operating everything from the windows to the seats and antenna.
In the early days of motoring various voltages were tried by manufacturers. There are twenty four volt, twelve volt and six volt cars found in the twenties. The Dodge Brothers were one manufacturer who equipped their cars with twelve volt systems early on, but along with the rest of the industry, they ended up with the six volt system which dominated in American cars until after the Second World War.
If you have ever seen the immense size of an early twelve volt generator you start to get an idea of why the six was standardized. Funnily enough, the twelve volt system was perfected in England and Europe very early and you find that almost all of those cars from the twenties on up have twelve volt systems.
Of course today we have the twelve volt system which uses an alternator, not a generator, to create its power, and the battery is a twelve volt sealed and unserviceable fixture that goes largely ignored during the car's first five or six years of service.
Unlike modern cars and batteries, the six volt batteries found in your antique or classic have to be cared for and nurtured if they are to perform for any longer than a few short months. A lot of the health of the battery depends on the health of the electrical and charging system which it is attached to, but before we get into that we'll run through the actual care and feeding of the battery itself.
Unlike modern sealed batteries, the old six volt batteries are not sealed. They are equipped with three caps which screw off to allow the replenishment of the water in the cells. As the caps are vented to allow the dissipation of hydrogen gas created in the cells, the level of electrolyte in the cells will diminish and need to be topped up with clear fresh water, preferably distilled. The cells should be filled to the bottom of the cap's guide and not allowed to overflow. If they do overflow protect your hands, wipe up the liquid quickly and throw away the rag as the liquid is a very strong and corrosive acid. It is a good idea to rinse the spill with copious amounts of water after putting the lids back on the battery, especially if the battery is in the car. One of the most heavily corroded areas in any old car is usually around the bottom of the battery and is a result of acid spills. Making sure that the battery and the area around it is rinsed well will avoid acid damage.
When you first install a six volt battery it will usually be topped right up with water. You should still check the fluid level however and continue doing so about once a week during the driving season. If you notice that the fluid level is dropping dramatically in one cell but not in others it can mean a problem with the battery, but if you notice the fluid level dropping in all the cells then the chances are that you have a generator problem. What happens is that the generator is overcharging and this results in the battery boiling off. In very short order the battery will be badly damaged and incapable of starting the car. This can happen to a brand new battery which is costly. Unfortunately this problem is one of the most common, most expensive and most easily rectified. The problem is that most mechanics who have been raised in the age of the alternator don't really understand the generator or know that most the output of most generators is adjustable. In many old cars the owner was required to adjust the output of the generator depending on which season the car was being driven in. During winter months when the car was driven more often in the dark than in the summer, the generator was turned up to provide more current to operate the lights without the battery losing charge.
In the summer, when the car was not driven as often in the dark, the generator output was turned down to avoid boiling the battery. Most current owners don't know this and spend the summer driving around with a generator that is putting out far too much current for the demand. One simple solution to this is to drive with the lights on which will use the excess current without damaging your battery.
Any car relying on a generator to produce its current should have an ammeter and or a voltmeter. This will clearly indicate what is happening with your charging system and is one of the best devices that you can use to save yourself a lot of money. Ammeters are the more common of the two devices but both are used in pretty much the same way.
When you are driving, your ammeter in a six volt car should show a zero charge. If it shows a minor negative charge you have a draw on your system which is demanding more current than your generator is providing, and you should either check the output of your generator or your voltage regulator. If they check out then it may be that you have a problem somewhere else and it should be tracked down. Prolonged driving with this problem persisting will end up in a dead or dying battery. If you notice that the needle is in the negative when the car is running at idle, rev the motor up to around fifteen hundred R.P.M. and hold it there for a moment. Many generators or regulators will not kick in until the engine revs over fifteen hundred. Once they kick in the generator should work at idle but don't think that an idling six volt car will charge its battery. The only way to charge a battery in a six volt car with the engine running is to take it out for a drive. Once around the block will not do it either. It should be a drive of a half hour or more.
If you have revved the car and the ammeter is still showing negative charge turn on your lights. If the needle drops further but the reading is stable turn your lights off. If the needle swings back to its original negative charge position and is stable then it's likely that the car is just running off the battery and the generator is not working at all. If you notice that the needle is indicating a negative charge but it is jumping around all over the place and unstable then it could be that your voltage regulator is cutting on and off and needs replacing. Either condition is hard on the battery.
Now if you are driving your car and notice that the ammeter is showing a positive charge you should immediately pull over and check your battery to make sure that the condition hasn't gone unnoticed long enough to boil the electrolyte. In severe cases a runaway generator will provide enough current to create enough gas in the battery to bulge the case and cause a risk of explosion. If you ever open the hood and you hear bubbling sounds coming from your battery and see that it is wet, immediately close the hood and leave the car turned off. Don't attempt to do anything until everything has cooled down. If a battery explodes, which is rare but it has happened, anyone near by is going to be covered in boiling acid. It is better to be safe than sorry. Most overcharge situations will be noticed long before they get that bad but they are still very hard on your battery. If you are driving and notice an overcharge and have checked the fluid level and it's all right then try turning on your lights to use up some of the extra power. If you have a long way to go and you can't get the charge down with just your headlights on, make sure that you replenish your battery with distilled water regularly during the trip, or better yet, call for the flatbed before something really expensive happens like a dead short and a fire.
In either a no charge or too high a charge situation, a roadside repair that sometimes works is to give the voltage regulator a tap with a screwdriver handle or similar implement. I don't suggest a ballpeen hammer no matter how tempting. This tap will sometimes loosen a sticky voltage regulator. If it does work, don't forget the problem. You should check or replace the regulator or at least carry a spare because it could be a warning of problems to come.
As with anything else, you should familiarize yourself with what the owner's manual has to say about your charging system. It can often be that the problems that you are experiencing are covered in weekly service or owner adjustments rather than in expensive electrical system repairs. Always remember that the easiest to fix and hardest to find problems with a car are usually electrical. Prevention of problems is always a lot cheaper than finding them later. There is nothing worse than having to spend a couple of thousand dollars finding a problem that takes less than a few minutes to fix once it is found.
In the next column we'll continue to explore the mysteries of faulty electrical systems from the standpoint of someone who doesn't know or have an interest in all the fancy terms like ohms and varying resistance, but just wants to proceed on down the road without toasting the car or ourselves.