Ways to prolong the life of a NiMH battery
NiMH or Nickel Metal Hydride batteries are an improvement over the older NiCd or Nickel Cadmium Batteries. The issue with Nickel Cadmium Batteries is that is suffers from what is called Memory Effect or the properly termed Voltage Depression. There isn’t really a “memory effect” but a depression of voltage caused by crystalline formations inside the battery. These crystals form when the battery cells are overcharged. NiMH batteries are less susceptible to these problems but they still do suffer from these problems. To prevent this and other problems and prolong your battery’s life, try these following things:
Cycle Charge. Cycle charging means to discharge a battery fully then recharge it to full capacity. When you open up a new pack of batteries, you should cycle charge them at least 3 times to reach its maximum performance. Also, cycle charge your NiMH batteries at least once every two weeks. This prevents the crystalline build-up inside the cells.
Do Not Mix With Other Cells. Do not mix NiMH batteries with Alkaline and Lithium Batteries. They behave differently and may have adverse effects on the cells. Plus, do not mix battery packs. Do not mix batteries from a pack to another. Battery packs are paired during the manufacturing process. Those with the same internal resistance and voltage output are paired in a pack. This prevents one cell damaging the other during usage. When batteries from different packs are used together, the battery with the weakest voltage output will degrade faster than the others.
Protect From Reverse Polarity. I mean two things, first is to never put a battery in the wrong polarity and the other is to keep the battery from being in a condition where its polarity is reversed. Reverse polarity can irreversibly damage a battery. Modern Electronic devices have a safety feature that automatically shuts down the device when the cells are below 0.9 volts. However, simple devices like flash lights and radios do not have this feature. When the device shows indications of low battery power, stop using them and remove the battery from the device.
Store in a Discharged State. If you do not plan to use your batteries for a long period of time, discharge them and store them in a cool dry place. Each cell have different self-discharge rate. Though they are small differences, this could cause a battery pack to be “uneven.” What will happen is the batteries will undergo self discharge and one cell will have more charge than the other. When you use them, the other cell will lose charge faster so the device you are using it for will stop working earlier even if the other cell still has charge. When you charge the cells, one will reach full charge before the other and will be overcharged. As pointed out earlier, overcharging can damage NiMH batteries.