Keeping our batteries in pairs, why?
As seen in the previous discussion, internal resistance in batteries reduces the ability of current to flow. Should one battery contain greater internal resistance than the other in the pair, that battery when called upon to work, will exert itself at an X factor compared to its counterpart. This increase exertion (in trying to keep up with its counterpart) will lead to an increase in internal resistance. As time goes buy, the internal resistance grows exponentially until battery failure occurs.
Because electrical current flows in a closed system, the battery with the lesser internal resistance is trying to push a golf ball through a garden hose (so to speak). This in turn causes an increase in internal resistance of the "good" battery. As the internal resistance in the "good" battery increases, the battery containing the greater internal resistance is stressed even more, once again increasing its internal resistance due to work. Why? Think of it as trying to fight your way through a jungle using a machete when compared to a walk in the park. Which one is less demanding?
[h=3]How do I ensure my batteries are kept in pairs?[/h]They are normally received from the manufacture that way. Once received mark the pair with a letter and a number e.g. A1 and A2.
[h=3]Is the number important and if so why?[/h]Yes it is. A natural phenomenon takes place in a stack that many cannot explain. The battery closest to the load will discharge quicker than its counterpart. Many theories have materialized over this, but for all practicality, we know it occurs and will leave it at that (in this discussion). You should alternate your batteries in subsequent uses. e.g. If A1 was used on top, A1 should be used on the bottom next time the set is used, and back on top for the following use, and so on, and so on... This will insure a greater distribution of the workload and a more natural and even build up of internal resistance, extending overall battery life. Think of it as rotating the tires on your vehicle, wearing them out evenly.