Nickel metal hydride battery (Commonly abbreviated to “Nimh battery”) has dominated the market today. This is because the battery chemistry is advanced in performance, safety, the cycle of life, and other parameters. In addition to that, manufacturers are working to improve the cell. The cell is designed to be used on electronic products that consider run time. As a result of this, it is used in a wide range of applications. Before you buy a cell, it is essential to not some of the useful factors. Let us see safety, usage, and differences of nickel-metal hydride.

Are NiMh Batteries Safe?

Generally, batteries are safe to buy you need to take precautions. Nimh is a nontoxic cell to human beings but harmful to other living things such as plants. However, the main problem is electrolytes. When exposing to extreme temperatures, electrolytes react with materials to create gas.

How to Keep NiMh Battery Safe?

Proper Charging

Proper charging means fully charging a cell according to the manufacturer’s rule. You can determine the completely charged battery by examining charge currents as well as recording charge time. Moreover, you must charge a battery at a moderate temperature. Extreme temperatures can cause an internal circuit. This produces heat thus makes the cell to be unsafe. You can buy a battery charger that measures temperatures. It will alert you when the temperatures rise.

Proper Storage

Cells are not stored inside a device. Remove the battery from the equipment and put it in the original package. In addition to that, store it in a cool dry place to avoid heat. Also, cells should not be put in contact, ensure they are separated.

Ventilation

It is recommended to ventilate the room for charging cells. Electrolytes are produced during charging and they emit hydrogen. The gas colorless and odorless hence you cannot recognize. The downside of hydrogen is that it is highly explosive. It mixes with oxygen in the air when produced. Since hydrogen is lighter than oxygen, it accumulates above oxygen. For this reason, it can result in a massive explosion in the room. On top of that, hydrogen can cause eye and skin problems.

Easy Safety Tips To Follow

• Cells should always keep devices away from children. This includes wrist watches, remote controls, thermometers, cards, and other products that have batteries.
• Do not expose lose batteries to pets and small children. Keep them away from access.
• Create awareness by teaching friends and parents on keeping cells away.
• If your child has swallowed a cell, run to the hospital, and do not give the child anything to drink.

What are NiMh Batteries Used For?

Mobile Phones

Nickel metal hydride has a greater density. The cell is designed to be a slim geometry. This gives an energy density of about 60Wh/kg. The cell takes up to 300 life cycles. Ways to increase cycles include draining and recharging the device for about four times.

Laptops

Laptops use several types of cells including nickel-metal hydride. The batteries work well in portable computers and last longer, unlike nickel-cadmium. If you want to increase the life cycle of nickel-metal hydride on a laptop, you should discharge more often.

Computers

Computers that use NiMH last longer. Also, they deliver great performance.

Digital Cameras

A good digital camera should work for long before it drains. Before the introduction of lithium-ion, most digital cameras used Nimh and still use.

What is the Difference Between A NiMh Battery and A Lithium-ion Battery?

Charge Cycles

The charge cycle is referred to as the charging and discharging process of a rechargeable battery. The lithium-ion battery has a powerful ability to perform longer charge cycles compared to nickel-metal hydride. This parameter contributes to the high cost of lithium-ion batteries. There are ways you can do to increase life cycles. For example, reducing the battery temperature, choose the right termination charge, prevent high charge, and discharge.

Voltages

Voltage is the characteristic of a cell. It is examined through chemical reactions, polarization, and components of a battery. The nominal voltage of a lithium-ion is about 3.70V. On the contrary, nickel-metal hydride operates at a nominal voltage of 1.2V in each cell. A high nominal voltage is great because it increases watt-hours.

High Power

Lithium-ion battery operates at higher voltage hence it delivers more power compared to nickel-metal hydride. NiMH produces has lower voltages that can support high power.

Chargers

Nickel metal hydride and lithium-ion need specific chargers. These chargers have different types of electronics. You cannot use a different charger on li-ion because it can result in accidents. Manufacturers have designed chargers that show currents, voltages as well as charge time. Also, it examines the rate of charging and cuts the process in case of issues. Conversely, nickel-metal hydride chargers do not come with safety parameters.

Size

Lithium-ion is a more advanced cell with less weight than most battery technology. Nickel metal hydride is among the heavy cells. Weight is a crucial factor to consider when it comes to transportation. Lithium-ion can be moved from one place to another without using much energy.

Dangerous

Nickel metal hydride is not as dangerous as lithium-ion. Nickel metal hydride does not cause a fire when exposed to oxygen. Lithium-ion explodes when exposed to oxygen. Therefore, it requires a protection circuit to guarantee safety.

Price

The most important thing when you buy a cell is checking the price of a product. The cost of lithium-ion is almost three times s more of other batteries. Nickel metal hydride is affordable. The rise of demand for cells in consumer electronics will make the price of lithium to go down.

Top Nimh Battery Manufacturers Recommend

Himax was founded in 2002 and started to produce nickel-metal hydride batteries, and successfully developed high power and Low-self discharge NiMH batteries. Now Himax Nimh batteries are widely used in applications that require higher power, such as radio control cars, toys, power tools (e.g. electric drill, saws, angle grinders, etc.), and some medical devices in the global market.

Compared to a lithium ion polymer (LiPo) battery, the nickel-metal hydride (NiMH) battery is a relatively safe battery as it is well designed in terms of safety performance due to its material and structure.

 

Generally, the NiMH rechargeable batteries rarely leak, unlike alkaline batteries. However, both alkaline and rechargeable batteries contain electrolytes, which could induce leakage when the batteries are used incorrectly.

 

By this logic, nickel-metal hydride batteries may explode. The principle of explosion is that the air pressure inside an object becomes too large, so the container cannot be contained.  When the container breaks, it results in an explosion as the air pressure is released in an instant.

 

If a battery is used improperly, there can be an overcharge/discharge, short circuit, and even increase in internal voltage.  To prevent the battery from exploding, a recoverable safety valve will open and reduce the internal pressure, thereby preventing an explosion.

 

What are NiMh batteries?

The nickel-metal hydride battery is mostly used in mobile-communication equipment, power tools, and medical equipment.

NiMH batteries are divided into high-voltage and low-voltage batteries. The high-voltage NiMH battery was first developed by M.Klein and J.F. Stockel in the United States in the early 1970s. Since then, there has been a tendency to replace nickel-cadmium with nickel-metal hydride batteries.

 

The positive electrode active material of Ni-MH battery is Ni (OH) 2 (called NiO electrode), the negative electrode active material is metal hydride, also called hydrogen storage alloy (the electrode is called hydrogen storage electrode), and the electrolyte is 6 mol/L potassium hydroxide solution.

 

The batteries are produced by different methods according to how they will be used. Different methods include the sintering, pulping, foam-nickel, fiber-nickel, and infiltration process.

 

Many batteries use the slurry-pulled negative electrode and the foamed nickel positive electrode to form the battery. The charge-discharge chemical reactions are as follows:

Positive electrode: Ni (OH) 2 + OH- = NiOOH + H2O + e-

Negative electrode: M + H2O + e- = MHab + OH-

Total reaction: Ni (OH) 2 + M = NiOOH + MH

 

Note:

• M: hydrogen alloy;
• Hab: hydrogen adsorption; the process from left to right is the charging process; the process from right to left is the discharging process.

Features of NiMh batteries

Low-voltage nickel-metal hydride batteries have the following characteristics:

The voltage is 1.2 to 1.3V, which is equivalent to that of cadmium nickel batteries. The energy density is high, which is also more than 1.5 times that of cadmium nickel batteries.

 

They can be charged and discharged quickly, and they have good low-temperature performance. They are sealable and have strong resistance to overcharge and discharge.  There is no dendrite formation, which prevents short circuiting.  Overall, low-voltage NIMH batteries are safe and reliable.

High-voltage nickel-metal hydride batteries have the following characteristics:

The batteries have better over-discharge and overcharge protection, can withstand higher charge-discharge rate and also does not have dendrite formation. The mass specific capacity is 60Ah/kg, which is 5 times that of nickel-cadmium batteries.

They also have a long cycle life (up to a 1000 cycles) and excellent low-temperature performance.  They are fully sealed and require less maintenance, and the capacity does not change significantly even at -10℃.

Preventing explosions from Ni-MH batteries

Below are just a couple of preventative measures to prevent NiMH batteries from exploding.

Avoid overcharging during use

Users should avoid overcharging because it is easy to cause the positive and negative electrodes in the battery to swell.  This will cause the active material to fall off, the separator and the conductive network to be damaged, and the battery ohmic (Ω) polarization to become larger.

Storage of NiMH batteries

The nickel-metal hydride battery should be fully charged. If the battery is stored for a long period of time, the function of the hydrogen storage alloy of the battery negative electrode weakens, which affects the battery life.

 

Learn more about Himax NiMH batteries

Himax’s nickel-metal hydride batteries are the world ’s leading level, offers up to 2 times the C-rate of same size standard Nickel Cadmium Batteries. Due to their higher discharge rate and energy density features, users can use on more powerful equipments and applications.

 

Himax offers are variety of NiMH Battery Cells with wide temperature ranges. These Cells provide new electrode development which allows for a wide temperature range and long life. The cells have good availability with a wide cell selection that includes stable and compatible sizes.

3 min read . Updated: 31 Oct 2016, 01:56 PM IST

Naomi Tajitsu, Norihiko Shirouzu

Toyota is all set to enter the growing all-electric car market having technology edge of lithium-ion battery that could equip it with more power without significant extra cost.

 

Toyota City, Japan: Engineers at Toyota Motor Corp say they have tamed volatile lithium-ion battery technology, and can now safely pack more power at no significant extra cost, giving the Japanese automaker the option to enter the growing all-electric car market.

While rivals including Tesla Motors and Nissan Motor Co began adopting lithium-ion battery technology nearly a decade ago, Toyota has largely held back due to concerns over cost, size and safety.

Lithium-ion batteries can be unstable and have been blamed for incendiary Samsung smartphones and smoking Dreamliner airplanes.

Having Toyota endorse lithium-ion will be a fillip for the developing technology, and gives the automaker the option to produce for an all-electric passenger car market which it has avoided, preferring to put its heft behind hydrogen fuel-cell vehicles (FCVs).

Toyota says its Prius Prime, a soon-to-be-launched plug-in electric version of the world’s top-selling gasoline hybrid, will use lithium-ion batteries, with enough energy to make the car go around 60 kms (37.3 miles) when fully charged before the gasoline engine kicks in. Because of different methodology in measuring a car’s electric mode range, the Prime’s 60 km range will be listed in the United States as around 25 miles (40.2 kms).

‘Safety, safety, safety’

Many lithium-ion car batteries use a chemical combination of nickel, cobalt and manganese. These store more energy, take a shorter time to charge, and are considered safer than other Li-ion technologies. But they can still overheat and catch fire if not properly designed, manufactured and controlled.

“It’s a tall order to develop a lithium-ion car battery which can perform reliably and safely for 10 years, or over hundreds of thousands of kilometers,” said Koji Toyoshima, the chief engineer for the Prius.

“We have double braced and triple braced our battery pack to make sure they’re fail-safe … It’s all about safety, safety, safety,” he told Reuters.

Toyota has mainly used the more mature nickel-metal hydride batteries to power the motor in the conventional Prius, widely regarded as the forefather of the ‘green’ car, though it did use some lithium-ion batteries from 2009 in its first plug-in hybrid Prius, around the time the first all-electric cars powered by lithium-ion batteries – such as the Tesla Roadster and Nissan Leaf – came on to the mass market.

Toyota’s confidence in its battery’s safety and stability comes from improved control technology that precisely monitors the temperature and condition of each of the 95 cells in its new battery pack.

“Our control system can identify even slight signs of a potential short-circuit in individual cells, and will either prevent it from spreading or shut down the entire battery,” said Hiroaki Takeuchi, a senior Toyota engineer involved in the development.

Working with battery supplier Panasonic Corp – which also produces Li-ion batteries for Tesla – Toyota has also improved the precision in battery cell assembly, ensuring battery chemistry is free of impurities.

The introduction of even microscopic metal particles or other impurities can trigger a short-circuit, overheating and potential explosion.

“The environment where our lithium-ion batteries are produced is not quite like the clean rooms where semiconductors are made, but very close,” Takeuchi said.

Battery experts say increasingly sophisticated systems that can track individual cell conditions are becoming closely-held trade secrets.

“State of charge management, safety management and algorithm development is becoming one of the higher tiers of proprietary internal development,” said Eric Rask, principal research engineer at Argonne National Laboratory, a US department of energy facility outside Chicago.

“It’s very internal, very strategic, and companies are seeing management algorithms as a competitive advantage.”

Falling prices

Toyota has also been able to shrink the size of each cell, for example, closing the distance between the anode and cathode, where active ions travel when charging and discharging.

This has doubled battery capacity to around 8.8 kilowatt hours, while only increasing the battery pack size by around two-thirds and its weight by a half.

Battery experts say lithium-ion battery cell prices have fallen by about 60% in five years to around $145 per kilowatt hour as larger-scale production has made them cheaper to make.

Falling battery prices have enabled Toyota to develop its more compact, efficient battery, while also adding more sophisticated controls into its battery pack, Toyoshima said. Toyota declined to say more on its costs.

While Toyota sees FCVs as the ultimate ‘green’ car, the United States and China are encouraging automakers to make more all-electric battery cars as they push alternative energy strategies.

“Developing lithium-ion batteries for both hybrids and plug-ins will enable us to also produce all-electric cars in the future,” said Toyoshima said. “It makes sense to have a range of batteries to suit different powertrains.” Reuters.

Several NiMH replacement hybrid car batteries we recommend.

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