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NiMH VS Lithium-Ion (Li-ion): a Battery Comparison

NiMH VS Lithium-Ion (Li-ion): a Battery Comparison

NiMH VS Lithium-Ion (Li-ion): a Battery Comparison

A battery is something that is used as a substitute for direct current. Batteries have been the backbone of the industry since the mechanical revolution. There is no denying the importance and usefulness of the battery. Because in society is powered by various electronic devices such as cell phones, two way radios, laptops, and cameras. All of these things use batteries. There are many battery types out there, and each type has its strengths and weaknesses. For this article, we will discuss and compare NiMH and Li-ion batteries. 

What is a Nickel-Metal Hydride Battery?

Nickel-metal hydride (referred to going forward as NiMH) batteries have largely replaced older nickel-cadmium batteries, which have been phased out due to environmental concerns. The cell of a NiMH battery consists of a positive cathode made of nickel hydroxide, a negative anode made of several metal alloys which store hydrogen atoms and an electrolyte solution made of potassium hydroxide.

Each cell in a NiMH battery delivers 1.2V of power. NiMH batteries are available in both sealed and vented (open) versions and are typically used in cell phones, camcorders, backup lighting, power tools, laptops, and hybrid cars.

NiMH Pros

    • High Energy Density: These have an average of 2200mAh (milliampere hours—the amount of current in milliamperes that it can give multiplied by the time in hours). This is greater than the 1500mAh seen in Li-ion batteries. These are the standard numbers in 1.2v NiMHs and 3.7v Li-ions.

Compatible: If you have ten gadgets using an NiMH battery, you can use a single pack to power them all—not simultaneously, of course. NiMH uses standard sizes so they are compatible with all devices using sizes such as AAA or AA. Compared to Li-ions, the sizes depend on the manufacturer or model of the device. I did see some AA size Li-ions around the market, so it may be worth checking them out.

Safe: They have less active materials compared to Li-ion batteries. NiMH can pop if they are overcharged too much or short circuit, but this is nothing compared to a Li-ion, which can potentially blow up!

Fully Dischargeable: By this, I mean these batteries can be brought down to 0 charge, if you can get them to reach that. They will still charge; just don't let them suffer from reverse polarity, or else they will be damaged.

NiMH Cons

High Self-Discharge Rate: NiMH lose a large percentage of their charge every month. The number is around 5% in the first week after the charge and about 50% in the first month. There are low self-discharge (LSD) rate types available. They are more reliable than the standard NiMH, but they have lower capacities, usually around 2000mAh.

Unreliable for Low-Load Devices: You should not use NiMH batteries for devices such as clocks. They will lose charge faster through self-discharge rather than the load. Use alkaline, Li-ion, or lithium batteries instead.

Low Voltage Output: Each AA cell can only give 1.2v, compared to Li-ion cells that can give 3.7v.

Long Charging Time: The standard charge time of a NiMH is 10–12 hours. Fast charging these cells can result in damage. Li-ion cells can be charged at around 1–3 hours, depending on capacity.

Sensitive to Extreme Temperatures: At extreme temperatures, NiMH voltage output will drop. Li-ion batteries can tolerate these temperatures to some extent.

What is a Lithium Ion Battery?

In a lithium ion (Li-ion) battery, the cathode is made of a lithium-metal oxide, a compound of lithium and another metal, while the anode is typically made of graphite coated with copper foil. The electrolyte is made of lithium salt in an organic solvent.

The cells in a Li-ion battery have a much greater energy density than NiMH batteries and are capable of generating an impressive 3.6V of power. All Li-ion batteries contain an integrated circuit used to control the input and output voltage of the battery. You can find Li-ion batteries in a variety of different uses, such as vehicles, power tools, and portable electronics such as laptops and cell phones.

Li-ion Pros

Reliable: These have a significantly lower self-discharge rate than a NiMH battery. As a result, they can be used for low-current devices like clocks or watches.

Small: They are smaller and lighter compared to NiMH batteries.

Higher Voltage Output: A single cell can deliver 3.7v while even two NiMH cells can only give 2.4v.

Faster Recharge: Li-ions can be charged in about 1–3 hours, depending on capacity. This is much faster than the 10–12 hours needed for NiMH batteries.

Temperature Tolerant: These can better withstand low temperatures and warmer environments compared to NiMH cells.

  • Higher Energy Density: This means that the battery carries more charge per gram than a NiMH battery.

Li-ion Cons

Lower Capacity: These have an average of 1500mAh compared to the 2200 mAH average of NiMH cells.

Incompatible: Different manufacturers make different sizes and shapes for Li-ion batteries, making them usable only to a specific set of devices. NiMHs have standard sizes.

Less Safe: Ions are a very active material. They can react easily and generate a lot of heat. That’s why there are circuits in those cells. They are used to check for voltage and temperature. In other words, the circuits prevent the cells from blowing up.

Not Fully Dischargeable: If a Li-ion battery gets fully discharged, it will be damaged. Yes, you can shock charge it, but its efficiency will decrease. Always keep this kind of battery charged above 50%.

Which is Better, NiMH or Lithium Ion?

While one isn't technically "better" than the other, there are a number of significant differences between these two chemistries. On the performance scale, Li-ion batteries outperform NiMH in most categories. They have a longer overall life cycle of five years, compared to the NiMH life cycle of two to five years. Li-ion batteries also charge much faster, perform better in extreme temperatures and hold their charge for much longer than NiMH batteries.

NiMH options, on the other hand, are much lower in cost than Li-ion batteries. They need very little maintenance, are more environmentally friendly and are free from the transportation regulations that Li-ion batteries must follow when being shipped.

Can I replace ni-mh battery with li-ion battery

Every battery is designed for its specific purpose and applications. But it can be replaced ni-mh batteries with li-ion batteries but practically it is not a good idea because ni-mh batteries are designed and these batteries are suitable for those applications which require high current draw as compared to lithium batteries.

What to consider when buying li-ion and ni-mh batteries

When choosing a battery, whether it is a lithium-ion battery or a nickel-metal hydrate battery, or one of the two, we must first look at the specifications of the battery. Its power, density, charging time, price, and lifetime should be taken into consideration. And if there is a li-ion vs ni-mh battery, then we should look at the characteristics of the two and compare the two. These are the things to keep in mind when buying a lithium-ion or nickel metal hydrate battery. 

 NiMH VS Lithium-Ion

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