Reconditioned Car Batteries
First, let's establish how a battery works. A battery is a tank with chemicals that produce electrons. These are called electrochemical reactions.
Batteries have two terminals. One terminal is marked (+), or positive, and the other is marked (-), or negative. In normal AA, C or D cell (flashlight batteries that you buy at supermarkets), the ends of the battery are its terminals.
In a large car battery... there are two heavy lead posts that act as the terminals. The speed of electron production by this reaction says how many electrons can flow between the terminals. Electrons flow from the battery into a wire, and must travel from the negative to the positive terminal for the chemical reaction to take place. That is why a battery can sit on a shelf for a year and still have plenty of power (unless electrons are flowing from the negative to the positive terminal, the chemical reaction does not take place).
Why use recondition car batteries?
Interesting, batteries that have been recharged do NOT last forever. There are only so many times that you can charge and recharge them. First they start to lose power and you find that there is less and less usable time that you have before you must charge again.
Some people have termed this as the memory effect. The term "memory" basically is described as the battery "remembers" its usual discharge point and superficially "needs" a charge whenever it hits that point. In other words, if you have a NICd that always gets discharged to only 50% of its capacity, it will eventually not run well below that 50% mark if you ever wanted to discharge it to a lower point.
NICd batteries have active cadmium
In a new NICd battery the active cadmium is present in finely divided crystals. The memory effect develops as these crystals grow and reduce the effective surface area of the cadmium.
So in conclusion, while a reconditioned battery may be cheaper to buy there's NO guarantee that it will last longer (than a new car battery) and in some cases, it may have been recharged no more than once which can shorten the actual life span of the battery.
You need to way the cost factor against its reliablity and the whether it was recharged by a reputable and professional outlet. You can find other helpful advice and information regarding torque converter lockup.