How to Discharge a NiMH Battery

A NiMH battery can be discharged down to 0.7 to 0.9 volts. Discharging it more than that will lead to destruction of the cell. All the cells in the packs may not be of the same voltage as their voltage may vary as the pack ages. It is important that no cell be discharged below 0.7 volt as this will lead to a reversed-polarity charge and render the cell useless. In order to discharge the NiMH battery properly, follow the simple steps described below.

Tools and Materials Required

  • Voltmeter
  • NiMH battery
  • Electronic device (to discharge NiMH battery) or a discharge tray ( it is used to discharge individual cells)

For personal safety, use

  • A pair of disposable gloves

Step 1 – Take Necessary Precautions

Use a pair of gloves to avoid contact with any leaking component while inspecting the cell. If the battery has a leak or has a broken casing, dispose it off immediately. This should be done because if the leaking content is ingested accidentally, it may lead to an irreparable damage. If such a thing happens, call the poison control team immediately so the damage may be controlled. As a precautionary measure, work in an open area with ample light settings and on a flat surface. This will give you a clear vision of all the electrical components. Also, before discharging the cell, read the instructions on it carefully. If, however, the instructions are not mentioned, revert to the Internet and search online.

Step 2 – Choosing the Correct Electronic Device

Before discharging the NiMH battery, it is essential that an appropriate electronic device be selected for its discharge. Keep the size if the battery in mind. If you have to discharge an AA battery, you can use a camera. If, however, it is an AAA battery, any toy can be used and vice versa. If you do not intend to use any electronic device like those mentioned earlier, simply buy an equalizer discharge tray.

Step 3 – Using a Voltmeter

After you are sure that the battery cell is not leaking, connect it to a voltmeter to check the number of volts in the battery. This will give you an exact idea of how many volts are present in the cell. If it is more than 0.9 volts, it can be discharged.

Step 4 – Inserting the Battery into the Device or Connecting to the Discharger

If the volts are more than above mentioned volts, place the battery into the selected electronic device. Switch the electronic device on. Let the device run. When it is no longer running, it is at this point the battery has been discharged. If you are using a discharge tray, connect the battery to the discharge tray. Switch it on and let it run until the lights of the discharge tray turn off. This in turn would mean that the battery cell has been discharged.

Step 5 – Check the Battery

Now, take the battery out of the electronic device or disconnect it from the discharge tray and connect it with the voltmeter. If the voltage is approximately 0.9 volts to 0.7 volts, the battery has been discharged properly and can be charged accordingly.