What Battery Chemistry Type is Better To Use With Power Tools?

There are three types of battery chemistries currently in use with power tools. They are NiCD, NiMH, and Li-Ion chemistries. The decision to choose one of the specific battery chemistry for your power tool depends on your application, the frequency of use, and the amount of power you need. Here is a brief breadown of the top benefits of each type:

Benefits	NiCd	NiMH	Li-ion
Life Span	Avg 5-10 years	Avg 3-5 years	Avg 1-3 years
Weight	Heavy	Medium	Light
Capacity – The higher the capacity rating, the longer your battery can last between charges (this is runtime).	Average runtime per charge	Highest -longest lasting runtime per charge	Good runtime per charge
Power per Charge	Average	Excellent	Good
Charge Time	Depends on Capacity	Depends on Capacity	Depends on Capacity
Environmentally Friendly	Ok	Good	Excellent
Economical	Lowest Cost	Average Cost	Highest Cost
Best Suited For	Home Owners	Contractors / Companies	Homeowners / Contractors / Companies

Here is a more detailed account of the 3 chemistry types…

The Nickel Cadmium (NiCd) battery is a popular choice for two-way radios, emergency medical equipment and power tools.

NiCd batteries have both their advantages and disadvantages:

Advantages of NiCD

Fast charge.
High number of charge/discharge cycles — if properly maintained, the NiCd provides about 1200 charge/discharge cycles.
Good load performance in low temperatures.
Long shelf life.
Simple storage and transportation — no special conditions exist for most airfreight
companies.
Forgiving if abused — the NiCd is is a rugged rechargeable battery.
Economically priced
Available in a wide range of sizes and performance options.

Disadvantages of NiCD

Low energy density — compared with NiMH.
Memory effect.
Environmentally unfriendly .
Has relatively high self-discharge.
Battery failure typical between 5-10 years based on usage.

The Nickel-Metal Hydride (NiMH) battery offers high energy density and the use of this chemistry is vastly more environmentally friendly than its counterpart NiCD batteries.

NiMH batteries have both their advantages and disadvantages:

Advantages of NiMH

30– 40 percent higher capacity over a standard NiCd.
Less prone to memory effect than NiCd. Periodic exercise cycles are required less often.
Simple storage and transportation — no transportation regulatory control.
Environmentally friendly — contains only mild toxins; profitable for recycling

Disadvantages of NiMH

Limited service life — if repeatedly deep cycled, especially at high load currents, the performance starts to deteriorate after 200 to 300 cycles.
Limited discharge current — although a NiMH battery is capable of delivering high discharge currents, repeated discharges with high load currents reduces the battery’s cycle life.
More complex charge algorithm needed
High self-discharge
Performance degrades if stored at elevated temperatures — the NiMH should be stored in a cool place and at a state-of-charge of about 40 percent.
About 20 percent more expensive than NiCd — NiMH batteries designed for high current draw are more expensive than NiCd.
Battery failure typical between 3-5 years based on usage.

The Lithium Ion battery is the lightest of all metals, has the greatest electrochemical potential and provides the largest energy density per weight.

Advantages of Li-ion

High energy density — potential for yet higher capacities.
Relatively low self-discharge — self-discharge is less than half that of NiCd and NiMH.
Low Maintenance — no periodic discharge is needed; no memory.
Lightweight compared to NiCd and NiMH.
Environmentally freindly.

Disadvantages of Li-ion

Requires protection circuit — protection circuit limits voltage and current. Battery is safe if not provoked.
Subject to aging, even if not in use — storing the battery in a cool place and at 40 percent state-of-charge reduces the aging effect.
Moderate discharge current.
Shipment of larger quantities of Li-ion batteries may be subject to regulatory control.
Expensive to manufacture — about 40 percent higher in cost than NiCd.
Capacity deterioration is noticeable after one year, whether the battery is in use or not.
Battery failure typical between 1-3 years based on usage.

Battery Chemistries by the numbers:

	NiCd	NiMH	Li-ion
Gravimetric Energy Density(Wh/kg)	45-80	60-120	110-160
Internal Resistance (includes peripheral circuits) in mΩ	100 to 200¹ 6V pack	200 to 300¹ 6V pack	150 to 250¹ 7.2V pack
Cycle Life (to 80% of initial capacity)	1500²	300 to 500^2,3	500 to 1000³
Fast Charge Time	1h typical	2-4h	2-4h
Overcharge Tolerance	moderate	low	very low
Self-discharge / Month (room temperature)	20%⁴	30%⁴	10%⁵
Cell Voltage(nominal)	1.25V⁶	1.25V⁶	3.6V
Load Current – peak – best result	20C 1C	5C 0.5C or lower	>2C 1C or lower
Operating Temperature(discharge only)	-40 to 60°C	-20 to 60°C	-20 to 60°C
Maintenance Requirement	30 to 60 days	60 to 90 days	not req.
Typical Battery Cost (US$, reference only)	$50 (7.2V)	$60 (7.2V)	$100 (7.2V)
Cost per Cycle(US$)¹¹	$0.04	$0.12	$0.14
Commercial use since	1950	1990	1991

1: Characteristics of commonly used rechargeable batteries

Internal resistance of a battery pack varies with cell rating, type of protection
circuit and number of cells. Protection circuit of Li‑ion and
Li-polymer adds about 100mΩ.
Cycle life is based on battery receiving regular maintenance. Failing to apply
periodic full discharge cycles may reduce the cycle life by a factor of three.
Cycle life is based on the depth of discharge. Shallow discharges provide more cycles
than deep discharges.
The discharge is highest immediately after charge, then tapers off. The NiCd
capacity decreases 10% in the first 24h, then declines to about 10% every 30
days thereafter. Self-discharge increases with higher temperature.
Internal protection circuits typically consume 3% of the stored energy per month.
1.25V is the open cell voltage. 1.2V is the commonly used value. There is no difference
between the cells; it is simply a method of rating.
Capable of high current pulses.
Applies to discharge only; charge temperature range is more confined.
Maintenance may be in the form of ‘equalizing’ or ‘topping’ charge.
Cost of battery for commercially available portable devices.
Derived from the battery price divided by cycle life. Does not include the cost of
electricity and chargers.