You have discovered the downside to rechargeable batteries. Actually there are two downsides.
First of all, a rechargeable battery usually doesn't put out quite the same voltage as a good alkaline one. For most devices the difference doesn't matter much, but it is slightly less. It also won't put out this voltage constantly as long as an alkaline. The run-time of something powered by rechargeables will be shorter.
Then there's the problem you have just encountered. You can't recharge the batteries forever. Eventually they simply stop holding a charge. (In fact, each time you recharge it, it holds the charge ever so slightly less.) Depending upon the type and size of the battery, this can be as few as 100 recharges or up to 1000. It varies this widely and there's no way to know how well your battery is going to perform, In fact, you could buy two "identical" rechargeable batteries and they could perform completely differently.
One trick to extending the life of a rechargeable - and you may already know this - is to try and completely drain it when you use it before recharging it. Some high-end chargers even have a way of doing this for you.
Still, all things being equal, I think you're much better off using rechargeable batteries. The ultimate cost is going to be way less than if you buy alkalines, and the impact on the environment is considerably less. In fact, discarded batteries are one of our worst pollutants in landfills and those little metal cylinders are probably going to still be there 10,000 years from now.
· 1 decade ago