Simple tips and hints to help you keep the battery ¨in your classic car in tip-top working order

Let’s face it, many classic cars are not used as basic, everyday transport — they spend a lot of their life safely stowed away in a nice, warm garage, waiting for the next time they’re fired up for a sunny weekend run or a club event. And as long as they get out on a regular basis, they will remain in fine fettle.

However, when that special event or sun-soaked Sunday afternoon beckons, it’s always disappointing when all you get is a loud buzz from the engine when you twist the ignition key. So instead of enjoying a Sunday cruise, you’re left juggling around your classic and your everyday car to get them close enough for a jump start — or you forget about cruising and pull the battery out of the car and plug it into a charger. Either way, your potential enjoyment has been ruined.

You can avoid that scenario by keeping on top of battery maintenance, or by employing an electrical helper.

First off, let’s look at how to check your battery and keep it in fine operating condition, then at the lazy man’s way of keeping a battery up to the mark.

Battery Checking

No matter the quality of the battery in your classic car, it has a limited life — undercharging, overcharging and continuous heat/cold cycles all conspire to shorten it. In older, classic cars, poor connections and earths can also put a battery under stress.

The first step towards battery maintenance is checking open-cell voltage. This can be accomplished with a dedicated battery tester or a volt meter. When an auto battery is fully charged — and with all electrical devices turned off — voltage across the terminals should register between 12.5 to 12.6 volts. When the battery is not fully charged — although still capable of turning over the engine — that can drop to around 12 volts. If on testing your battery doesn’t push out this much power, further checking is required.

If your battery is low on charge, you’ll need to charge it up before checking. Use a slow charger for this — some quick chargers can distort cell plates. Once everything is fully charged, you can go onto the next step.

For this you’ll need a hydrometer in order to check the specific gravity of the electrolyte. To use a hydrometer, pull off or unscrew the battery filler caps. If the levels are down in any of the cells, top up with distilled water — the minerals in plain tap water can slowly reduce the battery’s capacity. (If your car is fitted with a low maintenance battery you may not find any filler caps. These types of batteries are not supposed to require topping up although, of course, they will eventually consume all their water and die. Check under the battery maker’s stickers — sometimes fillers are hidden away.)

Once levels are correct, use the hydrometer to siphon up some electrolyte — it’s best to keep the end of the instrument in the battery filler opening to avoid dripping acid onto the car. We’d also advise rubber gloves and safety glasses; battery acid is very corrosive — it will also eat holes in your clothing, so take care. Spilt acid should be cleaned up immediately with water.

Once you have your sample of electrolyte, tap the hydrometer to allow any bubbles stuck to the float to release themselves. You can read the specific gravity as indicated on the hydrometer’s scale — read from the bottom of the meniscus. If fully charged, expect a specific gravity of at least 1.265. Check each cell in turn — it is important that they all show similar readings. If one or more cells is lower than the others by 0.05 or more, it’s time to buy a new battery.

Checking Connections

If everything tests A-okay and your car is still proving difficult to start, it’s time to check out connections — assuming that, of course, your starter motor is fully functional.

The first items to check are the battery clamps. Residue build-up can be removed by cleaning with a solution of cold water and baking soda — this will neutralise any acid around the clamp. Remove the clamps — if they prove difficult to remove, don’t bash them with a hammer, you may damage the soft lead post. Try some more baking soda and water — failing that, nip down to your local auto shop and pick up a battery clamp removal tool.

Once the clamps are free, clean the posts with baking soda and water. It also pays to clean the entire top surface of the battery with detergent — dust can accumulate water, which will conduct miniscule amounts of power from the positive to the negative post, even when the car is not being used.

A post-cleaning tool can be used to clean up the post; this is simply a small, double-ended wire brush. With this you’ll soon have the lead post gleaming. At this stage, some recommend a thin coat of petroleum jelly be applied to the post to minimise further acid build up.

After a thorough cleaning, re-install the clamps, making sure they are also nice and clean — do not over tighten the clamps.

If your battery clamps or their wires appear tatty, it’s a good idea to replace them. Don’t be tempted into using universal clamps — in my experience they are not good for anything other than a temporary repair. Buy proper, moulded clamps and only use good quality heavy-gauge automotive cable.

It is also worthwhile checking earth connections within the engine compartment as well. There aren’t too many of these on a classic car, and they are usually easy to spot and to check. Undo the connectors and check for surface rust where they meet the car’s body or ancillary — clean up the connecting point and the connecting plate and bolt or screw; these can be easily replaced if they look too rusty.

Once everything’s ship-shape, it should be an easy task to check battery levels at regular intervals and then, next time the road beckons, your classic car will spring into life immediately.

Another Approach

It’s quite common for many classic car enthusiasts to simply disconnect the battery if the car is not expected to be used for lengthy periods. While there’s nothing wrong with this method it can be messy and time consuming — unless a battery off switch has been wired into your car — as the clamps have to be replaced every time you use the car. This is especially inconvenient if a battery is awkwardly situated — buried away in the boot, for instance.

Leaving the battery disconnected will not, of course, guarantee that it will hold its charge indefinitely — so you could still hit the Sunday drive problem mentioned above.

Additionally, if you own a more modern classic, disconnecting the battery could also mean losing electrical settings for items such as seats, security devices and radio/CD players.

A better solution is to use an auto battery charger. This can be plugged into your garage, with the main charging unit mounted to the wall alongside your car. It only takes 20 minutes to attach permanent wiring to connect your battery to the charger — then you simply plug the charger into the car battery.

Unlike more conventional chargers, an auto charger will be of the trickle variety (it should not be used to charge a fully discharged battery) and, because of this, it will not generate dangerous gases during the charging cycle so there’s no need to remove the battery from the car. As a bonus, keeping your battery fully charged at all times will probably also extend battery life.

And, of course, when the next sunny Sunday beckons, you’ll have no need for jumper cables and conventional battery chargers.

NZ Classic Car’s editor swears by his auto charger — he doesn’t always have the time to drive his Lotus on a regular basis so, alas, it spends a lot of its time in the garage plugged into the charger. That way, when he does get a gap in his busy schedule the Lotus is always ready and raring to go.

Words and Photos: James Black