Memory effect is a term that is thrown around with talking about a itunes gift card battery, but there are a lot of misconceptions around what memory effect is. Memory effect is where batteries aren’t able to hold as much charge as they once could.
1) Over-Charging: Charging aa rechargeable batteries, even the best rechargeable batteries, for too long will result in the peak voltage dropping off much more quickly than it once used to. It would appear to an end-user that the battery capacity had in fact decreased, however this is not the case. The is more common in high-drain consumer electronics such as handheld devices and digital cameras. The device is expecting to see the higher voltage, else it produces a low battery warning or similar. Some electronic devices which are not high-drain may not even see any difference if the battery has a voltage drop. Over-charging is much more likely with cheap trickle (slow) chargers.
2) Age and Use: Shock horror, the more you use a rechargeable battery, the less effective it is due to chemical reactions! It doesn’t matter whether you run Duracell rechargeable batteries, or a no-name brand, eventually they are all going to be less effective than they once were. The thing to look out for is the number of expected recharges you can get out of a battery. Many of the Duracell rechargeable batteries will give you around 1000 charges before their life ends.
Looking at the grand scheme of things, this is potentially one full charge every day for a few years! Every rechargeable battery also has an effective life, before you will begin to see some degradation of capacity, once again a good rechargeable battery will give you at least a year or two. If you are a regular user of batteries you will make your cash back tenfold before requiring to purchase new batteries, in comparison to purchasing single use batteries.
Draining a battery to 0 volts (completely dead) can potentially cause damage, leading to a reduction in life of rechargeable batteries. If you obtain Duracell rechargeable batteries which potentially give you 1000 full charges and have a battery with 90% charge remaining, would you really want to flatten it fully with a charger (many do this for you) before recharging?
Use the batteries normally and when performance is no longer acceptable then just recharge them again. If this is truly bugging you then some of the top rechargeable battery chargers will let you discharge a battery to a specified voltage, before the recharging cycle begins. This is more friendly for the battery life than draining it completely to 0 volts and is similar to what would happen if you used rechargeable batteries in a digital camera. A digital camera will not drain them to 0 volts, it requires a certain voltage in order for the camera to switch on.
People are unnecessarily caught up stressing about memory effect, and things that look like memory effect. Duracell rechargeable batteries or any of the best rechargeable batteries will most likely do the job, so just run out and get some and stop worrying. Let’s say you spend $20.00 on 4 AA Duracell rechargeable batteries and give them only 100 of the 1000 suggested charges over a couple of years, which they will easily achieve, each battery will end up costing 5c a charge ($20.00 / 4 / 100).