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Ni-MH batteries, in theory, have no memory effect. However, you may find that the capacity of a Ni-MH battery is sloping after it is used for 100-120 times. Is this a memory effect? How to revitalize your Ni-MH batteries?

What is the memory effect of a rechargeable battery? The emergence of memory effect is the result of the decline in battery capacity. When you find that the capacity of your Ni-MH batteries is no longer sufficient, you know that the life of the batteries is ending. However, did you know that you can revitalize them with certain approach? Experiments have shown that you can discharge them totally, and repeat this procedure for several times. Most of the batteries can be revitalized.

Particularly when your Ni-MH batteries haven’t been used for a long time, the capacity of the batteries can be revitalized in this way. Also, you try to recharge it with high-current shocks. (Caution: the device has to be the one specially made for revitalizing the Ni-MH batteries. If you use the wrong device, explosion may occur.) Ni-MH batteries, as the main features of the internal resistance is small, have large discharge current, so many digital cameras use 1.2V Ni-MH batteries, especially the 3V power digital cameras. Two nickel-metal hydride batteries have the voltage of only 2.4V, but when the camera starts up, 2A current can be achieved.

When you use the Ni-MH batteries with insufficient capacity, the power detecting system of your camera may refuse to start up because of low power. I have been using Ni-MH batteries for four years, and they are still in sound condition. According to my records, the batteries had the highest capacity after they had been used for two months, about 100 to 120 times of recharging.

Actually, it is recommended that the Ni-MH batteries should be totally discharged and recharged every three months. After the batteries have been used for a long time, the internal electrode oxide layer has stronger resistance than it was. Therefore, they are not suitable for your digital camera. How can you reduce the resistance then? Very simple, as the method mentioned above, totally discharge them and recharge them for several times, until you find that your camera can be started up by them. If the batteries cannot be revitalized, you can try the follow approach. The specific procedure is:

1. Get a 20A resistor, 10-50Ω
2. Lay your batteries on the table, and use two lines of metal wire to connect to the each end of the resistor.
3. Connect the other ends of the wire lines to the each end of the battery.
4. Use a thermometer to monitor the temperature of the battery that is being discharged.
5. When the temperature of the battery rises to 100F, stop discharging and wait until the temperature goes back to room temperature again.
6. Discharge the battery until the voltage is lower than 1.0V.

Then, you can revitalize the other Ni-MH batteries.

Caution: This procedure is not suitable for the new Ni-MH batteries and other types of batteries. Don’t apply this approach until you know that you can understand the risks and can control them when you try to revitalize your Ni-MH batteries.

When you find that your batteries cannot be revitalized by this approach, they really come to the end of their life. Just throw them to the recycling bin.