Question

How many years NiMH batteries last?

Answer 1

Let us get some idea about NiMH batteries. A rechargeable nickel metal hydride battery $\left( {NiMH{\text{ }}or{\text{ }}Ni-MH} \right)$ is a type of battery. The positive electrode's chemical reaction is comparable to that of the nickel–cadmium cell $\left( {NiCd} \right),$ as both use nickel oxide hydroxide $\left( {NiOOH} \right).$ The negative electrodes, on the other hand, are made of a hydrogen-absorbing alloy rather than cadmium.

Complete answer:
$NiMH$ batteries can have two to three times the capacity of $NiCd$ batteries of the same size, as well as a substantially better energy density than lithium-ion batteries, but at a lower cost.
The charging voltage per cell is in the region of $1.4-1.6{\text{ }}V$. A constant-voltage charging approach can't be used for automatic charging in most cases. When fast-charging $NiMH$ cells, it's best to use a smart battery charger to avoid overcharging, which might harm the cells.
$NiMH$ batteries can typically be recharged hundreds of times, making them theoretically equivalent to hundreds of alkaline batteries in overall service life. The battery life, on the other hand, is limited to$\;5$ years or less.
Catalysts are used in modern $NiMH$ batteries to manage gases created by overcharging $(2{H_2} + {O_2}\xrightarrow{{catalyst}}2{H_2}O)$. However, this only works with up to 0.1 C overcharging currents (that is, nominal capacity divided by ten hours). This reaction heats up the batteries, putting a halt to the charging process.

Note:
$NiMH$ cells are commonly used in digital cameras and other high-drain devices, where they outperform primary (such as alkaline) batteries over the course of a single charge.
Because of their lower internal resistance, $NiMH$ cells are ideal for high-current-drain applications. With a $500{\text{ }}mA$ load, typical alkaline AA-size batteries, which have a capacity of around $2600{\text{ }}mAh$ at low current demand $\left( {25{\text{ }}mA} \right),$ only have a capacity of$1300{\text{ }}mAh$. $\left( {36th} \right)$ Digital cameras with LCDs and spotlights can quickly drain batteries by drawing over $1000{\text{ }}mA.$ These current levels can be delivered by $NiMH$ cells without a similar loss of capacity.