The battery is used via external connections for electrical power devices like mobile phones, electric cars, flashlights, etc. It consists of an electrochemical cell.
When the battery powers the electrical devices, it has a cathode and anode. Earlier, the term battery was meant to consist of multiple cells, but now it is usually referred to as consisting of a single cell.
There are two types of batteries primary and secondary. Primary batteries are disposable, while secondary batteries can be recharged again. Both NiMH and NiCd batteries are rechargeables.
NiMH vs NiCd
The difference between NiMH and NiCd is that the negative electrode used in NiMH is a hydrogen-absorbing alloy. While the negative electrode used in NiCd is cadmium. NiMH stands for Nickel-metal hydride battery, and NiCd stands for Nickel Cadmium battery. The discharging rate of NiMH is higher. While the discharging rate of NiCd is lower. NiCd batteries are more toxic than NiMH batteries. It releases chemicals like lead, mercury, and cadmium into the environment.
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NiMH or Nickel-metal hydride battery is a secondary battery which means that it can be recharged. The chemical reaction of NiMH in the positive electrode is very much the same as in NiCD, i.e., nickel oxide hydroxide (NiOOH).
The negative electrode used in NiMH is a hydrogen-absorbing alloy. It has a higher capacity and higher energy density.
But it is less than lithium-ion batteries. NiMH is resistive to explosion and leaking and is used as a substitute for the same shaped non-alkaline and non-rechargeable batteries.
NiCd stands for Nickel-cadmium battery. The abbreviation used for nickel-cadmium battery is derived from Nickel and Cadmium, and hence it becomes NiCd.
It is rechargeable better using cadmium as the negative electrode and nickel oxide hydroxide as the positive electrode.NiCd battery has a discharge of around 1.2 volts, and it decreases at the end of a discharge.
An electromotive force that is offered by the NiCd battery is 1.3 volts. This battery comes in various sizes and capacities, ranging from large ventilated cells to carbon-zinc dry cells.
Comparison Table
| Parameters of Comparison | NiMH | NiCd |
|---|---|---|
| Capacity | High | Low |
| Discharging rate | Higher | Lower |
| Cost | Expensive | Inexpensive |
| Toxicity | Less | More |
| Effect | Environment friendly | Not Environment friendly |
| Charging | Resists over-discharging and overcharging. | Simple and quick |
| Negative electrode | Hydrogen-absorbing alloy | Cadmium |
What is NiMH?
NiMH batteries were invented in the year 1967 when work and research began at the Battelle-Geneva Research Center.
NiMH batteries were based on the sintering of the NiOOH electrodes and Ti2Ni+TiNi+x alloys. Developing NiMH batteries as we know them was sponsored by two companies, Volkswagen AG and Daimler-Benz.
After developing the required and specific energy, patents were filed in various European countries, including Switzerland, Japan, and the United States. A patent was then transferred to Daimler-Benz.
NiMH batteries became famous, and interest in them was aroused during the 1970s when they were used in satellites.
Various companies like Philips, CNRS, and Ovonic Battery Co. tried to make NiMH batteries light-weighted to store the hydrogen and improvise the composition of Ti-Ni alloys.
In the year 2008, more than 2 million cars consisting of NiMH batteries were manufactured. NiMH batteries are bi-polar, which means that they avoid short circuits and have some advantages, like hydrogen storage in electric vehicles.
NiMH batteries can be charged fast, but they should be charged with the smart battery charger to avoid overcharging.
NiMH battery consists of a resettable fuse safety, which prevents the current or temperature from being too high.NiMh is considered better than the other types of batteries.
It is used in high-drain devices and digital cameras. It is advantageous because of its ability to draw high currents and low internal resistance.
NiMH batteries took the place of NiCd batteries because of their nominal charge capacity, operation on many devices, etc.
Lithium-ion batteries are considered better than NiMH batteries. It is used in hybrid and electric vehicles but is now superseded by Li-on batteries.
What is NiCd?
Waldemar Jungner invented NiCd batteries in 1899 in Sweden. When NiCd batteries were made, then its competition was lead-acid batteries.
In all the ways, Nicd batteries were better than it, like higher energy density, etc. Jungner substituted cadmium in place of iron. His work was not known in the United States.
After producing the flooded design in Sweden and using active materials, in 1946, the production of NiCd batteries was first started in the United States.
The batteries were called pocket type because of nickel-plated steel pockets.
In the mid of the 20th century, sintered Ni-Cd batteries became very popular because of their greater material surface area, lower internal resistance, and plates becoming highly porous.
Discharging rate of the NiCd batteries depend upon the different size like in a D-size battery, the discharge rate is 3.5 amperes, and in AA batteries, the discharge rate is 1.8 ampere.
NiCd batteries’ cell potential is nominal, i.e., 1.2 volts. The charging rate of the NiCd battery is very simple and quick and can be charged at different rates depending upon the cell.
Because of fast charging, the temperature of the batteries may rise, which can damage the cells. There is a risk of overcharging, and the life of the battery would be shortened.
The safe temperature range to use NiCd battery is between -20°C and 45 °C. When the Ni-Cd batteries are not in use, then it will self-discharge itself, which is one of its drawbacks.
Wet cell or Vented cell Ni-cd batteries were also invented in 1899. It is used for larger capacities because of its higher discharge rates.
It has wide applications like backup power for telecoms, aviation, mass transit, and rail, engine starting for backup turbines, etc.
Main Differences Between NiMH and NiCd
- The capacity of NiMH batteries is comparatively higher than NiCd batteries.
- The discharging rate of the NiMH batteries is higher. The discharging rate of the NiCd battery is lower.
- The cost of NiMH is expensive. While NiCd is cost-effective.
- NiMH batteries are less toxic. NiCd is more toxic and releases chemicals like cadmium, mercury, nickel, etc.
- NiMH batteries are more environmentally friendly than NiCd.
- NiCd batteries resist over-discharging and overcharging. While NiMH battery charging is very simple and quick.
- The negative electrode used in NiMH is a hydrogen-absorbing alloy. The negative electrode used in NiCd is Cadmium.
- https://www.sciencedirect.com/science/article/pii/S0956053X05000176
- https://ieeexplore.ieee.org/abstract/document/4018094/
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Piyush Yadav has spent the past 25 years working as a physicist in the local community. He is a physicist passionate about making science more accessible to our readers. He holds a BSc in Natural Sciences and Post Graduate Diploma in Environmental Science. You can read more about him on his bio page.
