Edit: This is by far the most popular post on this blog. unfortunately it has become a bit dated and it seems that the only batteries you can find for sale at the moment are silver-calcium. If you have an older car I suggest that you buy a decent multi stage battery charger and charge your car battery once a month or so to prevent the problems described below. Also see What Causes Car Batteries to Fail for more information.
About two and a half years ago Battery Centre sold me a silver calcium battery for my car. According to them silver calcium batteries are the best thing in lead acid battery technology since Gaston Planté made the first one in 1859.
They are probably right and most new cars will be fitted with one and the battery should last 3 to 5 years. If you have an older car things are not that simple. If your older car was fitted with a “hybrid” or plain lead acid battery originally, you will find that a silver calcium battery will probably not give you the life expected from it.
Today my expensive silver calcium battery gave up the ghost completely at least six months before its time after about two weeks of nursing and nightly additional charging.
Being a techie I did not sit idle during the two weeks and did a bit of extra research about car batteries. Most people who have dealt with car batteries know that your car’s lead acid battery is not really 12 volt but 12.6 volt and you need about 14.2 to 14.4 volt to properly charge it. If you use too low a voltage to charge the battery it will never get a full charge and too high a voltage will cause the battery to gas and lose electrolyte (water). A too low charge will also cause something called acid stratification as well as sulphation in the battery causing it to fail sooner than expected.
Unlike normal lead acid batteries, silver calcium batteries need 14.8 volt to properly charge. This means if your car wasn’t fitted originally with one its charging system will never fully charge a silver calcium battery because the charging system is set to 14.4 volt not 14.8 volt. Guess what happens? Yes you’re right, the silver calcium battery dies a premature death due to sulfation and acid stratification.
Battery Centre will happily sell you an expensive silver calcium battery and even tell you it is not really a problem because the battery will simply run in your car with a slightly lower charge. (http://www.batterycentre.co.za/SilverCalciumBattery.htm) They happily neglect to tell you that sulfation and acid stratification is a problem when you operate a battery continuously in a state of low charge. To be fair it does get a mention elsewhere on their site but not where they are punting the silver calcium batteries.
Dodgy marketing practices on their website is probably par for the course but Battery Centre’s staff really should think long and hard about dismissing a customer as ignorant when he tells them he doesn’t want a silver calcium battery because it is not the correct battery for his car. Anyway the proper battery was R200 cheaper at Midas across the road.
Read all you ever wanted to know about batteries at http://www.batteryuniversity.com