Nickel Metal Hydride Rechargeable Battery - Disposal and Comparison

Nickel metal hydride (NiMH) batteries are rechargeable batteries that offer several advantages over other battery technologies. NiMH batteries are more environmentally friendly than different batteries, and they can be recycled or disposed of safely. NiMH batteries also have a higher energy density than other batteries, making them ideal for use in high-drain devices such as digital cameras. In this article we will discuss pros and cons, and how to dispose when needed. 

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Table of Contents 

Nickel metal hydride battery advantages and disadvantages

Nimh battery shelf life

When should I replace my NiMH batteries?

In conclusion 

Nickel Metal Hydride Battery Advantages and Disadvantages

The performance is excellent. Inside the NiMH battery, a wide range of metal materials are utilized, all of which have good electrical conductivity and can withstand high-power discharge. The specific power has recently exceeded 1500W/kg.

The low-temperature performance is quite good. The inorganic electrolyte system is employed, and the low-temperature performance of lithium batteries is surpassed.

The technology is well-established. Currently, commercial hybrid electric vehicles include Toyota Prius and Honda Insight hybrids, which utilize nickel-metal hydride batteries.

The management system is quite simple. There is no need to check the voltage of each battery since the battery has a high resistance to overcharge and over-discharge. The battery can achieve self-equilibrium during charging via the side reaction with the consumed gas (oxygen), so there is no need for a particular equalization circuit.

A high energy storing capacity, low pollution, resistance to overcharging and over-discharging, as well as a high recovery value

But there are also some disadvantages.

The battery's thermal effect The nickel-metal hydride battery has a significant drawback. Its usage puts a strain on the batteries. There are two primary reasons for this. One is that the charging reaction of the NiMH battery is exothermic, and heat is generated during charging; the other is that charging efficiency is low, and the heat generated by self-discharge is more significant.

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The charging efficiency of a defective NiMH battery is lower than 100%, even when it is in an empty condition. When the charging capacity reaches 80%, the reaction speed increases rapidly, and the heat production rate rises quickly. It will lead to thermal runaway issues. The higher the charging current, the less efficient it becomes, and the more heat will be produced. NiMH batteries have a high energy density and are often used in high-power applications, which increases the heat generation rate.

The battery's particular energy is generally 50 to 70 Wh/kg, which is 2 to 3 times lower than lead-acid batteries. Although it is 2 to 3 times greater than lithium batteries, there is a significant difference compared with them.

The nominal voltage is unusually low. The 1.2V offered by the power supply system for automobiles, which consists of several volts, necessitates more batteries in series, increasing battery consistency and dependability.

The charging efficiency is poor at high temperatures. The charge efficiency decreases with increasing temperature, and the reaction efficacy pushes the battery temperature higher. Thermal runaway may eventually occur, and safety concerns may arise due to the decrease in charge efficiency.

Nimh Battery Shelf Life

You should keep NiMH batteries in a cool, dry place with little humidity and no corrosive gasses. Metallic parts can rust and battery fluid leak due to expansion or contraction in organic component parts if batteries are stored in a humid location where temperatures drop below - 20°C or rise above +45°C.

Long-term storage may accelerate battery self-discharge and cause reactants to deactivate, leading to the deactivation of batteries. Places with a temperature range of +10°C to +30°C are ideal for long-term storage.

When reactants are deactivated, and the battery is recharged for the first time after long-term storage, battery voltage and capacity may drop. Repeat cycles of charging and discharging to return batteries to their original performance. To avoid leaks and deterioration in performance due to self-discharge, charge your batteries at least once a year if you intend to store them for longer than that.

When should I replace my NiMH batteries?

The following symptoms might indicate that your rechargeable batteries need to be replaced.

●The battery has been utilized a lot recently, and after charging, its operational time has begun to decrease. It is recommended that you replace your rechargeable batteries if the operating time is halved.

●One battery is charging when the other is being discharged. If one battery's charging time grows more extended, for example, if it takes ten times as long to charge as another charged battery of the same type. It's a good idea to replace rechargeable batteries that take more than double the amount of time to charge as compared to newer rechargeable batteries.

Suppose a dead battery has to be replaced in an appliance. In that case, it's preferable to replace all batteries in the used gadget rather than risk overcharging the other batteries. However, suppose there is a recurrent contact between battery and terminal in the cases below. In that case, the primary reason may be an intermittent connection.

●Battery charging is never completed or takes an inordinately long time  (2 to 3 times longer than regular charging.)

●The battery's operating duration is significantly shortened, even if you've only used it a few times.

It is crucial to clean the plus and minus terminals of batteries and the charger's terminals with a cleaning cloth in the situations described above.

In Conclusion 

NiMH batteries have several advantages and disadvantages that should be considered when purchasing. NiMH batteries are more expensive than lead-acid batteries. Still, they last longer and can be used in high-power applications. However, NiMH batteries have poor charging efficiency at high temperatures, leading to safety concerns. When storing NiMH batteries, keeping them in a cool, dry place with little humidity is vital. Long-term storage may accelerate battery self-discharge and cause reactants to deactivate. If you notice any of the symptoms described above, it is time to replace your NiMH batteries.