Released On 29th Jul 2015

NiMH vs Li-Ion Batteries

UPDATED 11/06/2025

Our guide to NiMH vs Lithium-ion batteries answers your questions about longevity, power, battery charging cycles, self-discharge, memory effect and much more. 

For many years, right up to the early 1990s, most portable devices were powered by nickel cadmium (NiCad) batteries. While NiCad batteries were cheap and easy to recharge, they weren't especially powerful and they contained toxic substances that are bad for the environment.  

NiMH and Lithium-ion (Li-Ion) batteries have now largely replaced Ni-Cad batteries, dominating the battery market for two-way radios.

As a major battery supplier for many years, our experience in this area will help to dispel any confusion as you shop our site for your two-way radio batteries. 

This updated guide includes real‑world metrics like cycle life, self‑discharge rates, and behaviour in extreme temperatures — all tailored to two‑way radio users.

Q: What does NiMH stand for?

A: NiMH stands for Nickel Metal Hydride. Nickel is a dense metal related to iron.

Q: What does Li-Ion mean?

A: Li-Ion means Lithium Ion. Lithium is a lighter metal – in fact, it’s the lightest metal there is.

Q: What are the biggest differences between the two types of battery?

A: Size, weight, power output and memory effect are the biggest differences:

* Life cycle: the number of times the battery can be recharged before losing capacity.

**Standard NiMH batteries lose charge quickly in storage, but modern LSD, or "low self-discharge" types keep power for months.

Size and weight

For a battery of each type with the same storage capacity, a NiMH battery will be smaller, but much heavier, than a Li-Ion battery (the weight difference can be approximately 20% - 35%). For most two-way radio users, especially for handheld two-way radios that you carry around with you, weight is more important than size.

Power output

Each NiMH battery cell can deliver about 1.2V of power, putting them at a disadvantage to lithium-ion batteries, which have one of the highest energy densities of any modern battery type, delivering around three times the output, or 3.6V per cell. 

Memory effect

NiMH batteries also suffer much more than Li-Ion batteries from "memory effect", which can diminish a battery's capacity to hold a full charge over time. We describe memory effect more fully below.

Field & Temperature Performance

Performance in Extreme Conditions
NiMH batteries operate reliably in −5 °C to +35 °C, sometimes beyond, while standard Li‑ion capacity can drop to about 12% at –40 °C — often failing below –5 °F. Li‑ion is also less tolerant of high ambient heat and requires controlled storage conditions. 

Voltage Stability Under Load
Li‑ion batteries maintain a flatter discharge curve — useful for heavy PTT bursts — whereas NiMH battery voltage can drop during heavy use, which may reduce signal strength mid-shift or during long transmissions.

To summarise this technical comparison, Li‑ion packs store around twice the energy per kg, offering longer run‑time on handheld radios, while NiMH imposes a 20–35% weight penalty for the same capacity.

Q: What is “memory effect” in a battery?

A: NiMH batteries suffer from something called “memory effect”. What this means is that if you frequently recharge a battery while it’s only partially discharged, the battery will effectively "memorise" the decreased life cycle, losing its original capacity for a full charge.

The shortened usage time of a radio between charges could create problems for a business, for example where users are working long shifts.

Solution: Use a smart charger designed for NiMH batteries - these detect when the battery is full by monitoring small changes in voltage and temperature, helping to prevent overheating and damage.

To sum up NiMH batteries:

• Can suffer from memory effect if not discharged periodically.
• Low Self-Discharge (LSD) variants hold their charge better during storage.
• Use a NiMH smart charger that stops charging automatically when the battery is full - this prevents overheating and helps the battery last longer.

Li-Ion batteries, however, suffer from hardly any memory effect – there’s no need to wait for the battery to completely discharge; you can recharge it any time you want with very little effect on its future charge capacity. 

(One small caveat to this is that it’s a good idea to fully charge a brand new Li-Ion battery before first use, and it’s a good idea to let it discharge completely from time to time - battery experts recommend this after every 30 charges.)

To sum up Li-ion batteries:

• No memory effect.
• Should not be fully discharged regularly.
• Use a Li-ion smart charger with built-in protection — it helps manage the battery safely and prevents overcharging.

Q: What’s “self-discharge”?

A: Self-discharge is the gradual loss of battery charge over time, either because it is not being used, or owing to environmental conditions such as heat or cold. 

On average, NiMH batteries self-discharge at a rate of between 5% and 20% on the first day, and up to 4% per day thereafter at room temperature , but at 45°C, the discharge rate can be three times that.  

By contrast, Li-ion batteries self-discharge at a rate of around 5% on the first day, and then approximately 1.5% to 2% per month. Again, this is greatly affected by heat and cold; extremes of either will increase the self-discharge rate. Scientists are working hard to improve battery endurance at lower temperatures, so we can expect to see this reflected in real-world self-discharge rates in the future.

Q: Does one battery type have a better charge cycle than the other?

A: Opinions differ a little but generally, lithium-ion rechargeable batteries have greater longevity than NiMh batteries, at around 700 to 950 charge cycles compared to between 500 to 800 charge cycles for NiMH batteries. 

Q: Is one type of battery more expensive than the other?

Cost and sustainability

A: NiMH battery packs typically cost less than half the price of equivalently rated Li‑ion packs.
They also use fewer toxic metals (no cobalt or manganese), and are easier to recycle. 

Li‑ion requires stricter disposal protocols due to chemical regulation and safety labelling.

Q: Weren’t there rumours about Li-Ion batteries catching fire?

A: Stories abounded in the early years of Li-ion batteries about them bursting into flame. It’s true that there was a problem with the chemistry in the batteries back then – if the battery was accidentally over-charged there was a chance it could overheat and set itself on fire. But in 1996 the chemical formula was changed; Lithium-Cobalt-Oxide was replaced by the much safer Lithium Iron Phosphate, a formula with very low combustibility. It's probably still a good idea not to leave your two way radio charging indefinitely though. Remove it from the charger as soon as possible after it's fully charged.

Q: What does mAh stand for?

A: mAh stands for milli Amp hour and is a measure of a battery's energy storage capacity. The greater the battery's mAh, the more power it can hold. An mAh rating can be used to compare the energy capacity between batteries of the same type such as two NiMH batteries.

Safety features and transport restrictions

Modern Li‑ion battery packs include Battery Management Systems (BMS), built-in safety features that prevent overcharging, overheating, or short circuits. 

However, Li‑ion remains regulated - air or sea shipping often requires special packaging and documentation. NiMH batteries typically avoid these restrictions .

Should you choose a NiMH or Li-ion battery? 

• Choose Li‑ion for lightweight, all‑day use in temperate climates where high capacity and fast charging matter.
• Choose LSD NiMH for rugged, cold‑weather, or cost‑sensitive operations, especially where shipping and environmental impact are concerns.
• Dual‑battery strategy: carry a Li‑ion for field shifts and an LSD NiMH backup where reliability and shipping flexibility are needed.
• Charger recommendations: Use smart chargers for NiMH, and BMS-enabled smart chargers for Li‑ion.

If you need help choosing the right battery for your two-way radio, please contact us for assistance.

• Browse for Motorola batteries
• Browse for Motorola battery chargers

Tags: Li-Ion Batteries, NiMH Batteries