Difference Between NiMH and NiCd
Difference Between NiMH and NiCd
The sheer popularity of these rechargeable batteries often raises the question, “What’s the difference between NiCAD and NiMH batteries?”
To summarize, the main differences between NiCAD and NiMH batteries deal with capacity, memory effect, and environmental friendliness.
NiCd (Nickel Cadmium) batteries were once the best option when looking for rechargeable batteries. They are better than lead acid batteries and come in standard sizes for most gadgets. Nowadays, NiMH (Nickel Metal Hydride) batteries are slowly replacing NiCd batteries in many applications due to a number of reasons. The biggest, and most significant, difference between NiCd and NiMH batteries is capacity. A typical NiMH battery can have a capacity that is two to three times higher than that of a typical NiCd battery. A larger capacity means longer intervals before charging or fewer spares needed for those who need a lot of power.
Although NiMH batteries have higher capacities than NiCd batteries, it would not last as long when used in low current applications like remotes and clocks. This is because of NiMH’s higher self-discharge rate of roughly 30% per month to NiCd’s 20%. The self-discharge rate is the rate at which the battery loses its capacity without any load applied. The applications mentioned above consume much less than the self-discharge rate. The appliance being powered is therefore much less of a factor with the rate at which the battery discharges.
Nickel-Cadmium (NiCAD) Batteries
The world’s first NiCad battery was developed by a Swedish scientist in 1899. Needless to say, there have been many improvements since then.
A standard nickel-cadmium battery is composed of a nickel(III) oxide-hydroxide positive electrode plate, a cadmium negative electrode plate, a separator, and a potassium hydroxide electrolyte.
Common uses: Some popular applications of NiCAD batteries are toys, emergency lighting, medical equipment, commercial and industrial products, electric razors, two-way radios, power tools, and more.
Benefits: Here’s an overview of some of the advantages of NiCAD batteries:
- Relatively inexpensive
- Charge very quickly, simple to charge
- Easy to store, easy to ship
- Take a high number of charges
- Functional in low temperatures
Drawbacks: And here are some of their shortcomings:
- Not as powerful as some other rechargeable batteries
- Self-discharge while in storage
- Contain toxic metals that are harmful to the environment
Nickel-Metal Hydride (NiMH) Batteries
NiMH batteries are a much more modern phenomenon. Research and development began at the Battelle-Geneva Research Center in 1967, and was satisfactorily completed in 1987.
The chemical composition of a standard nickel-metal hydride battery looks like this: a nickel hydroxide positive electrode plate, a hydrogen ion negative electrode plate, a separator, and an alkaline electrolyte such as potassium hydroxide.
Common uses: These include automotive batteries, medical instruments, pagers, cell phones, camcorders, digital cameras, electric toothbrushes, and other low-cost consumer devices.
Benefits: Here’s a look at a few of the advantages of going with a NIMH battery:
- Quite a high capacity compared to other rechargeable batteries
- Resists both over-charging and over-discharging
- Extremely lightweight construction
- Friendly to the environment: no hazardous chemicals like cadmium, mercury, or lead
- Drawbacks: And here are some of the limitations:
- More expensive than other rechargeable models
- Self-discharge rapidly while in storage
- Cut power suddenly rather than a slow trickle down
- Some only work with manufacturer’s charger
Choosing the correct battery for your application is critical. When making this decision you may need to ask yourself the following questions:
- 1, How much room do I have?
- 2, How much weight can my application handle?
- 3, How many amps will I be using under full load?
- 4, How much “run-time” do I need?
- 5, How fast do I need to recharge?
