How often have you thought 'I had a new battery last spring, but it doesn't seem very lively now that the frosts are back again'. With an older battery, you might start to think 'I think I will have to replace my battery soon - it's lost it's sparkle'.
The answer could well lie in your own hands.
This short article is aimed at helping you to get the best from your new or decent battery.


New Batteries - Shelf Life

Especially with 'our' sorts of car, the seller of batteries does not sell a high volume of units. A battery for 'your' car could well sit on the shelf in the stores for months.

During that time the residual voltage will deteriorate slightly. This will particularly be the case if the battery terminals are not covered with plastic isolators. Somewhat surprisingly the battery discharges through the air. Only in a vacuum, would that fail to happen.

For example: A brand new twelve volt battery will have a potential of around 12.7 - 12.8 volts when fully charged. Re-charging this battery before using it would be pointless as it would be already well charged.

After 4 months on the shelf that brand new battery could be down to 12.45 - 12.55 volts. Consequently thorough charging before use is very sound practice.

Existing Batteries - Memories

Well-used batteries also form memories when their capabilities have not been used for some time. This is most likely after winter lay-up.

Without any charging the battery may have been at 70% charge for a significant time - possibly 3 months. The battery forms a barrier at 70% and will work up to that 70% very willingly, but to get that top missing 30% to work is very difficult, possibly impossible if the barrier/memory is very established.

Such will almost certainly be the case when 6 to 9 months inactivity is involved. The time-scales themselves are obviously variable for individual instances and also will vary from battery to battery.

Another way in which a battery can form a memory is if it is fitted to a car with an under-performing charging system for a considerable time span. This can happen because of various prevailing conditions such as.
· Poorly set up regulator
· Slipping fan belt unable to deliver all of the required power for full output.
· Car always used for short journeys thus not giving enough time for the full charging job to get done.
All of these prevent the full charging taking place, so the top percentage of charge grows accustomed to no activity. In time this will refuse to be available.

Batteries also discharge through the air and if air is damp this takes place more quickly. Sometimes if no plastic terminal covers are used during storage the charge passes from the negative post to the positive post, carrying with it any particles of dirt which will then be deposited on the positive post (in much the same way as electro-plating takes place) thus making this post appear very black.

Getting an accurate reading of battery state

If you are going to use a voltmeter there a multitude of rules to understand otherwise you will get misleading readings, that is why I encourage the use of the hydrometer because it never misleads.

Most folks find it difficult to understand just how long it takes for a modern battery trickle- charger to charge a car battery. They think that because their mobile phone battery can be refreshed in one hour the same applies to the car battery. The fact is that one of our car batteries is up to 10,000 times larger than the mobile phone. This seems to evade them.

In reality then

If you put a partially charged battery straight on to your car it will likely have more than enough umph to crank and start the engine.

However, when your charging system kicks in, it will only re-charge the battery to the level at which it was installed.

On-going performance

Consequently you will have a battery with a bit less umph than you paid for. The 'loss' of power may not be significant whilst the battery is fairly new, but after a couple of years you might start to notice a lack of sparkle - especially in winter conditions.

Prevention

To get best advantage from your newly-purchased battery - before fitting, or your existing battery before re-connecting - it should be trickle-charged for at least a few days in well-ventilated conditions. Only when fully charged should it be installed on the vehicle. Clearly such a timescale is not always convenient, but you must decide how best to balance the equation for your needs.

Interim solution

Why not pinch the battery off the wife's car for the immediate event whilst your battery is charged fully up to strength. The walking will help her 'keep-fit' programme!

Mike Palfreyman