Ni-MH and Ni-Cd rechargeable batteries - basic data (voltages, sizes, specifications)

Ni-MH batteries were relatively slow to enter mass production - although hydrogen is very well suited for the anode, the design of cells using hydrogen requires absolute tightness and high pressure inside the cell. It was only in the late 1960s that it was discovered that alloys of certain metals could "store" hydrogen atoms, which could then participate in reversible chemical reactions. In modern Ni-MH batteries, the anodes are made from an alloy of many metals, such as vanadium, titanium, zirconium, nickel, chromium, cobalt, and iron (interestingly, the reason for the better performance of such exotic alloys is not entirely clear - their compositions are determined experimentally).

Table of Ni-MH Battery Voltages

model symbol	specification
	voltage [V]	height [mm]	diameter / dimensions [mm]
R03 (AAA)	1.2	44.5	10.5
R6 (AA)	1.2	50.5	14.5
R14 (C)	1.2	50	26.2
R20 (D)	1.2	61.5	34.2
6F22 (9V)	8.4	48.5	26.5 x 13.1

Basic facts about Ni-MH batteries:

• anode: rare earth metal alloy or nickel with many other metals
• cathode: nickel hydroxide
• electrolyte: potassium hydroxide
• applications: mobile phones, video cameras, emergency lighting, power tools, laptops, high current portable devices

Ni-MH batteries have replaced older Ni-Cd batteries

Aside from the anode, the design of Ni-MH batteries is essentially the same as that of the older Ni-Cd batteries they replaced. Even the voltage (1.2V per cell) is identical, which means that in many applications these batteries can be used interchangeably.
Compared to Ni-Cd batteries, Ni-MH batteries achieve about 30% more capacity and also have a higher energy density (theoretically 50%, practically about 25%). Basic characteristics of Ni-Cd batteries:

• anode: cadmium
• cathode: Ni(OH)2
• electrolyte: KOH

The anode is coated with nickel, while the cathode is made of cadmium. The use of cadmium was the main reason for the withdrawal of Ni-Cd batteries from retail circulation.

The electrolyte (KOH) serves solely as a conductor of ions and does not participate in the chemical reactions occurring inside the cell. For this reason, a larger amount of electrolyte is unnecessary, which contributes to reducing the weight of the cells. Sometimes NaOH was used instead of KOH as an electrolyte - it does not conduct ions as well, but has a significantly lower tendency to cause leaks.

Ni-Cd batteries were characterized by good performance in applications requiring higher currents and/or low temperatures, long lifespan and storage time, as well as a longer self-discharge time than (standard) Ni-MH batteries.

Next-generation Ni-MH batteries

All cells (batteries and rechargeable batteries) self-discharge over time, even when not in use. In conventional nickel-hydride batteries, this effect is clearly visible. By optimizing the rechargeable cell technology, Sanyo has achieved great success in minimizing the self-discharge effect in ENELOOP batteries.

The chemical breakdown of the cathode has been significantly reduced by using a new "superlattice" alloy. An additional benefit of the "superlattice" alloy is the increase in the electrical capacity of the battery and the reduction of internal resistance, allowing for higher discharge currents. Another advantage of the "superlattice" alloy is the reduced cobalt requirement for stabilizing the compound structure. The anode, on the other hand, has been reinforced by using a new material, which has reduced natural disaggregation. Additionally, the separator and electrolyte have been optimized for low self-discharge.

The ENELOOP battery is a technology that ensures optimal energy use even over long periods: after 5 years, 70% of the charged energy remains available to the user. This is why ENELOOP is the first rechargeable battery that is charged and ready to use at the moment you buy it. ENELOOP can be used exactly like a traditional alkaline battery right after purchase. Even in low-power devices, where the self-discharge effect was a problem for batteries, such as TV remotes, alarm clocks, or flashlights.

This is certainly the greatest advantage of ENELOOP over disposable batteries: it can be recharged 1800 times and then easily recycled. As a result, it turns out that this technology is not only more economical but also allows us to avoid the troublesome recycling of 1800 batteries.

We encourage you to read our article: What are the differences between the 1.2V Ni-MH battery and the 1.5V alkaline battery

Next-generation batteries from other leading manufacturers:

• Energizer Extreme
• Duracell StayCharged
• GP ReCyko
• Varta Ready2Use
• Panasonic Evolta

Read more about next-generation Ni-MH batteries

Our offer: Ni-MH Batteries

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