The battery in your car is very old technology – dating back to 1830. The fact that they are still used in your car is a testament to what a good design they are.
They fulfill all the requirements of a rechargeable battery – they have a high energy density, they are cheap, and they may be cycled many times without loss of performance.
As with any rechargeable battery, however, there a few things we must consider and a few questions we must ask.
1. Do they have a memory effect?
The answer is no. This is a problem with nickel cadmium batteries, which I will discuss later, but not with car batteries.
2. Should they be fully cycled on a regular basis?
This is connected with the first question and the answer again is no. In fact, unlike most rechargeable batteries, you will prolong their life by keeping them in their fully charged state. If a car battery is kept in its discharged state for very long, it will die. This is important if, for example, you have a car that you aren’t using for a while. If the battery goes flat, and stays in that state for very long, you will will find that you cannot recharge it.
3. Can a battery be overcharged?
The answer is yes. This won’t happen in your car unless your regulator is malfunctioning, but it may happen if you are using a car charger. If you have a smart charger, it will detect when the battery is charged and turn itself off
But if you have an older style constant current charger, be careful. If it’s left on too long, then once be battery is fully charged, the potential will ramp up high enough to begin electrolising the acid, producing hydrogen and oxygen gas. This will kill your battery very quickly, as this process generates a lot of heat, and will result in the plates in the battery warping and short-circuiting.
So if your car isn’t being used regularly, invest in a smart charger, or perhaps a trickle charger, which you mount to the car, and then simply plug in to your 240 V outlet.
More on car batteries tomorrow.