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High C-rate Ni-MH Batteries


A nickel metal hydride (Ni-MH) battery is similar to a nickel cadmium (NiCd) battery, but it has higher capacity, less memory effect, and lower environmental pollution (or more simply, it doesn’t have the toxic cadmium) than the NiCd battery. Its recycling efficiency is better than that of lithium-ion batteries, and it is known as the most environmentally friendly battery.

The discharge performance of NiMH batteries can also meet the needs of most electronic products, and it is particularly suitable for products that require stable voltage over long discharge times.

High C-rate

Typically, high C-rate Ni-MH batteries can be charged at 1C and be fully charged in just over an hour. When discharged with a current of 5C, the median voltage of the battery can reach more than 1.24V and still discharge over 90% of its capacity.

Ni-MH batteries are efficient in their fast charging and high current-discharge performance, which makes them especially suitable for the high current discharge of electrical appliances, such as power tools, large toys (car toys, remote control aircraft) and so on.

Charging efficiency

The charging efficiency is the ratio of the capacity of a battery discharged under certain discharge conditions up to a certain cut-off voltage to the capacity of the battery input, which can be calculated according to the following formula:

Ni-MH battery's charging efficiency formula | Grepow
the battery’s charging efficiency formula

Because the input energy is partially consumed in the side reaction to produce oxygen, the charging efficiency is affected by the charging rate and the environmental temperature. The charging current must be within a certain range when charging: if the current is too small or too large, the charging efficiency will be low.

High charge rate

A Ni-MH cell has many similar characteristics to its NiCd counterpart, and it also follows a similar discharge curve to that of the NiCd. However, the Ni-MH battery is intolerant of overcharging, which can result in reduced capacity.

In order to ensure the best battery life, 1C charging is the recommended charging rate. After fast charging, it is recommended to use 0.03-0.05C trickle charging to compensate for self-discharge and maintain battery capacity.

High discharge rate

Himax’s Ni-MH batteries can offer up to 2 times the C-rate of similarly sized, standard NiCd batteries. Due to their higher discharge rate and energy density characteristics, users can use Himax’s Ni-MH batteries in more powerful devices and applications.

The following picture is the discharge curve of :

NiMH UP43SC2000 Performance Measurement Data Plots | Grepow
UP43SC2000-15C Performance Measurement Data Plots

Here are some specifications of Himax Ni-MH battery:

specifications of Grepow NiMH battery

There are three different series for Himax’s Ni-MH batteries that correspond to thor different discharge rates:

LP series, which stands for low power, means that the medium discharge rate is within a 5C rating. HP series stands for high power, and it has a discharge rating of 10C. Finally, the UP series, standing for ultra high power, has a discharge rate of 15C or more.

The above information comes from Himax, the manufacturer of Ni-MH, LiPO, and LiFe batteries. For more information, please further explore our blog or contact us at sales@himaxelectronics.com.