NiMH Batteries: What Are They?

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What are NiMH Batteries? Nickel-metal hydride batteries are a type of rechargeable battery. They’re used in lots of different devices, from cars to toys to smartphones.

They have a lot of advantages over other types of batteries, and they’re pretty popular because of that. But what are they really?

What are NiMH Batteries

In this post we'll cover:

The History of NiMH Batteries

The Invention

Back in 1967, some bright sparks at the Battelle-Geneva Research Center had a brainwave and invented the NiMH battery. It was based on a mix of sintered Ti2Ni+TiNi+x alloys and NiOOH electrodes. Daimler-Benz and Volkswagen AG got involved and sponsored the development of the battery over the next two decades.

The Improvement

In the 70s, the nickel–hydrogen battery was commercialised for satellite applications, and this sparked interest in hydride technology as an alternative to bulky hydrogen storage. Philips Laboratories and France’s CNRS developed new high-energy hybrid alloys incorporating rare-earth metals for the negative electrode. But these alloys weren’t stable in alkaline electrolyte, so they weren’t suitable for consumer use.

The Breakthrough

In 1987, Willems and Buschow made a breakthrough with their battery design, which used a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1. This battery kept 84% of its charge capacity after 4000 charge–discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed.


The Consumer Grade

In 1989, the first consumer-grade NiMH cells became available, and in 1998, Ovonic Battery Co. improved the Ti–Ni alloy structure and composition and patented their innovations. By 2008, over two million hybrid cars worldwide were manufactured with NiMH batteries.

The Popularity

In the European Union, NiMH batteries replaced Ni–Cd batteries for portable consumer use. In Japan in 2010, 22% of portable rechargeable batteries sold were NiMH, and in Switzerland in 2009, the equivalent statistic was around 60%. But this percentage has dropped over time due to the increase in manufacture of lithium-ion batteries.

The Future

In 2015, BASF produced a modified microstructure that made NiMH batteries more durable, allowing changes to the cell design that saved considerable weight and increased the specific energy to 140 watt-hours per kilogram. So the future of NiMH batteries looks bright!

The Chemistry Behind Nickel-Metal Hydride Batteries

What is Electrochemistry?

Electrochemistry is the study of the relationship between electricity and chemical reactions. It’s the science behind batteries, and it’s how Nickel-Metal Hydride (NiMH) batteries work.

The Reactions Inside a NiMH Battery

NiMH batteries are made up of two electrodes, a positive and a negative. The reactions that occur inside the battery are what make it work. Here’s what’s happening:

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  • At the negative electrode, water and a metal combine with an electron to form an OH- and a metal hydride.
  • At the positive electrode, nickel oxyhydroxide is formed when nickel hydroxide and an OH- combine with an electron.
  • During charging, the reactions move from left to right. During discharging, the reactions move from right to left.

The Components of a NiMH Battery

The negative electrode of a NiMH battery is made up of an intermetallic compound. The most common type is AB5, which is a mixture of rare-earth elements like lanthanum, cerium, neodymium, and praseodymium, combined with nickel, cobalt, manganese, or aluminium.

Some NiMH batteries use higher-capacity negative electrode materials based on AB2 compounds, which are titanium or vanadium combined with zirconium or nickel, and modified with chromium, cobalt, iron, or manganese.

The electrolyte in a NiMH battery is usually potassium hydroxide, and the positive electrode is nickel hydroxide. The negative electrode is hydrogen in the form of an interstitial metal hydride. Nonwoven polyolefin is used for separation.

So there you have it! Now you know the chemistry behind NiMH batteries.

What is a Bipolar Battery?

What Makes Bipolar Batteries Unique?

Bipolar batteries are a bit different than your standard batteries. They use a solid polymer membrane gel separator, which helps to prevent short-circuits from happening in liquid-electrolyte systems. This makes them a great choice for electric vehicles, as they can store a lot of energy and keep it safe.

Why Should I Care About Bipolar Batteries?

If you’re looking for a battery that can store a lot of energy and keep it safe, then a bipolar battery might be the right choice for you. They’re becoming increasingly popular for electric vehicles, so if you’re in the market for one, you should definitely consider a bipolar battery. Here’s why:

  • They’re designed to prevent short-circuits from happening in liquid-electrolyte systems.
  • They can store a lot of energy, making them ideal for electric vehicles.
  • They’re becoming increasingly popular, so you can be sure you’re getting a quality product.

Charging Your NiMH Batteries Safely


When you’re in a rush and need to charge your NiMH cells, it’s best to use a smart battery charger to avoid overcharging, which can damage cells. Here are some tips to keep in mind:

  • Use a fixed low current, with or without a timer.
  • Don’t charge for more than 10-20 hours.
  • Use a trickle charge at C/300 if you need to keep your cells in a fully charged state.
  • Use a lower duty cycle approach to offset natural self-discharge.

ΔV Charging Method

To prevent cell damage, fast chargers must terminate their charge cycle before overcharging occurs. Here’s how to do it:

  • Monitor the change of voltage with time and stop when the battery is fully charged.
  • Monitor the change of voltage with respect to time and stop when it becomes zero.
  • Use a constant-current charging circuit.
  • Terminate charging when the voltage drops 5-10 mV per cell from the peak voltage.

ΔT Charging Method

This method uses a temperature sensor to detect when the battery is full. Here’s what to do:

  • Use a constant-current charging circuit.
  • Monitor the rate of temperature increase and stop when it reaches 1 °C per minute.
  • Use an absolute temperature cutoff at 60 °C.
  • Follow the initial rapid charge with a period of trickle charging.

Safety Tips

To keep your cells safe, here are a few things to keep in mind:

  • Use a resettable fuse in series with the cell, particularly of the bimetallic strip type.
  • Modern NiMH cells contain catalysts to handle gases produced by over-charging.
  • Don’t use a charging current of more than 0.1 C.

What is Discharge in Rechargeable Batteries?

What is Discharge?

Discharge is the process of a rechargeable battery releasing energy. When a battery is discharged, it releases an average of 1.25 volts per cell, which then declines to about 1.0-1.1 volts per cell.

What is the Impact of Discharge?

Discharge can have a few different impacts on a rechargeable battery. Here are some of the most common ones:

  • Complete discharge of multi-cell packs can cause reverse polarity in one or more cells, which can permanently damage them.
  • Low voltage-threshold cutouts can cause irreversible damage when cells vary in temperature.
  • Self-discharge rate varies greatly with temperature, where lower storage temperature leads to slower discharge and longer battery life.

How to Improve Self-Discharge?

There are a few ways to improve self-discharge in rechargeable batteries:

  • Use a sulfonated separator to remove N-containing compounds.
  • Use an acrylic acid grafted PP separator to reduce Al- and Mn-debris formation in separator.
  • Remove Co and Mn in A2B7 MH alloy to reduce debris formation in separator.
  • Increase the amount of electrolyte to reduce hydrogen diffusion in electrolyte.
  • Remove Cu-containing components to reduce micro-short.
  • Use PTFE coating on positive electrode to suppress corrosion.

Comparing NiMH Batteries to Other Types

NiMH Cells vs. Primary Batteries

NiMH cells are the go-to choice for high-drain devices, like digital cameras, ’cause they outlast primary batteries like alkaline ones. Here’s why:

  • NiMH cells have a lower internal resistance, meaning they can handle higher current demands without losing capacity.
  • Alkaline AA-size batteries offer 2600 mAh capacity at low current demand (25 mA), but only 1300 mAh capacity with a 500 mA load.
  • NiMH cells can deliver these current levels without any capacity loss.

NiMH Cells vs. Lithium-ion Batteries

Lithium-ion batteries have a higher specific energy than NiMH batteries, but they’re way more expensive. Plus, they produce a higher voltage (3.2–3.7 V nominal), so you need circuitry to reduce voltage if you wanna use them as a drop-in replacement for alkaline batteries.

NiMH Battery Market Share

As of 2005, NiMH batteries were only 3% of the battery market. But if you’re looking for a battery that’ll last, they’re the way to go!

The Power of NiMH Batteries

High-power Ni–MH Batteries

NiMH batteries are the way to go if you’re looking for a reliable and powerful source of energy. They’re commonly used in AA batteries, and they have a nominal charge capacity of 1.1-2.8 Ah at 1.2 V. Plus, they can operate many devices designed for 1.5 V.

NiMH Batteries in Electric and Hybrid-Electric Vehicles

NiMH batteries have been used in electric and hybrid-electric vehicles for years. You can find them in the General Motors EV1, Toyota RAV4 EV, Honda EV Plus, Ford Ranger EV, Vectrix scooter, Toyota Prius, Honda Insight, Ford Escape Hybrid, Chevrolet Malibu Hybrid and Honda Civic Hybrid.

The Invention of the NiMH Battery

Stanford R. Ovshinsky invented and patented a popular improvement of the NiMH battery and founded Ovonic Battery Company in 1982. General Motors purchased Ovonics’ patent in 1994 and by the late 1990s, NiMH batteries were being used successfully in many fully electric vehicles.

The Patent Encumbrance of NiMH Batteries

In October 2000, the patent was sold to Texaco, and a week later Texaco was acquired by Chevron. Chevron’s Cobasys subsidiary provides these batteries only to large OEM orders. This created a patent encumbrance for large automotive NiMH batteries.

So, if you’re looking for a reliable and powerful source of energy, NiMH batteries are the way to go. They’ve been used in electric and hybrid-electric vehicles for years, and they’re still going strong. Plus, with the invention of the NiMH battery, you can be sure that you’re getting the best quality product. So, what are you waiting for? Get your NiMH batteries today!

What are Nickel-Cadmium (NiCAD) Batteries?

The world’s first NiCad battery was invented by a Swedish scientist way back in 1899, and since then, there have been plenty of improvements. So what are these batteries made of?


NiCAD batteries are composed of:

  • A nickel(III) oxide-hydroxide positive electrode plate
  • A cadmium negative electrode plate
  • A separator
  • A potassium hydroxide electrolyte


NiCAD batteries are used in a wide variety of products, such as:

  • Toys
  • Emergency lighting
  • Medical equipment
  • Commercial and industrial products
  • Electric razors
  • Two-way radios
  • Power tools


NiCAD batteries have plenty of benefits, such as:

  • They charge up quickly and are easy to charge
  • They’re easy to store and ship
  • They can take a high number of charges
  • But, they do contain toxic metals that can be harmful to the environment

So there you have it, NiCAD batteries are a great way to power up your gadgets and gizmos, but just make sure to dispose of them properly when you’re done!

Everything You Need to Know About NiMH Batteries

NiMH batteries are the new kids on the block, having been developed in the late 1960s and perfected in the late 1980s. But what are they and why should you care? Let’s take a look!

What’s in a NiMH Battery?

NiMH batteries are made up of four main components:

  • A nickel hydroxide positive electrode plate
  • A hydrogen ion negative electrode plate
  • A separator
  • An alkaline electrolyte like potassium hydroxide

Where Are NiMH Batteries Used?

NiMH batteries are used in a variety of products, from automotive batteries to medical instruments, pagers, cell phones, camcorders, digital cameras, electric toothbrushes, and more.

What Are the Benefits of NiMH Batteries?

NiMH batteries come with a ton of perks:

  • High capacity compared to other rechargeable batteries
  • Resists over-charging and over-discharging
  • Environmentally friendly: no hazardous chemicals like cadmium, mercury, or lead
  • Cut power suddenly rather than a slow trickle down

So if you’re looking for a reliable, eco-friendly battery, NiMH is the way to go!

Lithium vs NiMH Batteries: What’s the Difference?

What Are the Best Applications for NiMH Battery Packs?

Are you looking for a battery pack that won’t break the bank? NiMH battery packs are the way to go! These packs are perfect for applications that don’t require a super high-energy density, like cell phones, medical devices, and electric vehicles. Plus, you don’t have to worry about the potential hazards associated with lithium products.

Don’t NiMH Batteries Self-Discharge and Are Prone to the Memory Effect?

NiMH batteries have been around since the early 1970s and have a good safety and reliability record. While they don’t need a complex Battery Management System (BMS) like lithium batteries do, you can still get a BMS for your NiMH pack to help it last longer and communicate with your device. And don’t worry, NiMH batteries don’t self-discharge or suffer from the memory effect.

Will NiMH Batteries Last as Long as a Lithium Battery?

NiMH batteries have a good cycle life performance, but they don’t last as long as lithium batteries. However, they are still a great option if you’re looking for a cost-effective solution.

Does an Enclosure for NiMH Custom Battery Pack Need Venting Similar to Lithium Chemistry?

No, NiMH battery packs don’t need venting like lithium chemistry.

Do I Really Need a BMS for NiMH Battery Pack?

No, you don’t need a BMS for your NiMH battery pack, but it can be helpful. A BMS can help your battery pack last longer and communicate with your device.

What is the Difference in NiMH vs Lithium in Overall Cost and Battery Pack Size?

When it comes to cost and size, NiMH battery packs are the way to go! They are more cost-effective to design and manufacture, and they don’t require a complex BMS like lithium batteries do. Plus, they don’t take up as much space as lithium batteries, so you can fit more of them in the same area.


Nimh Batteries Vs Alkaline

When it comes to NiMH vs. alkaline, it really depends on your needs. If you’re looking for a quick and reliable power source, then rechargeable NiMH batteries are the way to go. They can last up to 5-10 years, so you’ll save a ton of money in the long run. On the other hand, if you need a battery for a low-drain device that will last a few months, then single-use alkaline batteries are the way to go. They’re cheaper and more convenient in the short term. So, when it comes to NiMH vs. alkaline, it really depends on your needs and budget.


Do NiMH batteries need a special charger?

Yes, NiMH batteries need a special charger! Charging NiMH cells is a bit trickier than NiCd cells, since the voltage peak and subsequent fall that signals a full charge is much smaller. If you charge them with a NiCd charger, you run the risk of overcharging and damaging the cell, which can lead to reduced capacity and a shorter lifespan. So, if you want your NiMH batteries to last, make sure you use the right charger for the job!

What is a disadvantage of using this NiMH batteries?

Using NiMH batteries can be a bit of a drag. They tend to cut power suddenly when they run out of juice, rather than slowly fading away. Plus, they self-discharge quickly. So if you leave one in a drawer for a couple of months, you’ll have to recharge it before you can use it again. And if you need high power or pulsed loads, like on GSM digital cellular phones, portable transceivers, or power tools, you’re better off with a NiCad battery. So if you’re looking for a battery that’s reliable and long-lasting, you might want to look elsewhere.

Is it OK to leave NiMH batteries fully charged?

Yes, it’s totally fine to leave NiMH batteries fully charged! In fact, you can store them indefinitely and they’ll still have plenty of juice when you’re ready to use them. No need to worry about them losing their charge over time. Plus, if you do find that they’re a bit low, just give them a couple of charge/discharge cycles and they’ll be good as new. So go ahead and leave those NiMH batteries fully charged – they won’t mind!

How many years can NiMH batteries last?

NiMH batteries can last you up to 5 years, but it all depends on how you store them. Keep them in a dry place with low humidity, no corrosive gases, and at a temperature range of -20°C to +45°C. If you store them in a place with high humidity or temperatures below -20°C or above +45°C, you might end up with rust and battery leakage. So, if you want your NiMH batteries to last, make sure you store them in the right place! Plus, if you want them to last even longer, charge them at least once a year to prevent leakage and deterioration. So, if you take good care of your NiMH batteries, they can last you up to 5 years.


NiMH batteries are a great way to power your electronics and are becoming increasingly popular. They’re reliable, long-lasting, and environmentally friendly, so you can feel good about using them. Plus, they’re easy to find and relatively inexpensive. So, if you’re looking for a new battery for your device, NiMH is a great choice. Just remember to use the right charger, and don’t forget to say “NiMH” with a smile – it’s sure to make your day a little brighter!

Hi, I'm Kim, a mom and a stop-motion enthusiast with a background in media creation and web development. I've got a huge passion for drawing and animation, and now I'm diving headfirst into the stop-motion world. With my blog, I'm sharing my learnings with you guys.