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I have a question about car batteries.

I often hear people say the sealed batteries are best because you don't have to keep checking them, and topping up with distilled water. The same people say that a 3 year life is normal.

My last two batteries each lasted 7 years and neither were sealed. And it was pretty unusual if they required topping up. They were normal batteries - one came with the car (Hyundai) and the second was an off the shelf replacement.

What are your thoughts?

Alan

From the "Ask Jack" archives - 27 August 2009

Safety and convenience have played a big part in bringing sealed batteries to the market.

The two big advantages of a sealed battery are the acid / water mix cannot "boil off" when exposed to extreme heat meaning potentially harmful gases are contained and not able to drift through the engine bay or cabin, and for the car owner, no regular topping up of the battery is required.

A recent survey carried out by the AA Battery Service of 1000 batteries of various brands and specification replaced by their mobile service, showed that the average life was 4 to 4 ½ years.

As you can appreciate, there were extremes at both ends of the spectrum that showed some batteries lasting as little as 2 ½ years up to 8 years.

The newer calcium sealed batteries have only been available as a replacement option in NZ for around 5 years and fitted to new cars as original equipment since 1997, so the life expectancy is still difficult to gauge with any real accuracy.

The life of a battery is governed by its use. Either extreme high or low use will reduce its life expectancy. For example, we are aware of one new car distributor in NZ who will only honour warranty on a battery if the vehicle has travelled a minimum of 6,000kms per annum while another only offers a two year / 40,000km whichever occurs first warranty.

It's interesting to note that many people still believe that a battery's main job is to start the engine. To help reduce excessive battery load (particularly on a cold start), most of the modern fleet are fitted with reduction geared starter motors which draw less power from the battery and therefore help lengthen their life.

These same vehicles however, have on-board computers and accessories fitted that draw current from the battery on a continuing basis (engine running or stationary).

Industry standards are to test a battery at half its Cold Cranking Amperage (CCA) rating. That is, if a battery is rated at 500 CCA, it is tested with a load of 250 CCA for 15 seconds. This test is calculated to allow for extreme variables that may influence the performance of the battery.

If the test shows that the voltage is being held at 9.6 volts or better, it is considered
to be in serviceable condition.