A ToolCrib.com visitor asked us recently: “What is the difference between NiMH and NiCd and which is best when using 220v power to charge battery?”

So. To tackle the first part of the question we have to look at the criteria for making the power tool battery decision. And then bring Lithium Ion into the equation to round out the choices.

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Criteria for Making Your Power Tool Battery Decision
According to Building a Better Power-Tool Battery you should be looking at a battery’s run time, life cycle, volts and amp-hour rating.

Run Time:
Quite simply run time is the amount of work a tool can do before its charge runs out.

Life Cycle:
Life cycle is how many times the battery can be recharged during its life time.

Volts (Power):
Volts will determine work output of the tool. John Sara, cordless product manager for Milwaukee Electric Tool, quoted in the article I linked to above says “Individuals currently using a 18-volt NiCad battery, should see 2 – 21/2 times more work output from a V28.”

Amp-Hour Rating
The higher the Amp-Hour rating the longer the battery lasts – be aware that power tool batteries of the same voltage will often have different Amp-Hour ratings.

NiMH vs. NiCad vs. Li Ion: Picking What’s Right for You

Nickel metal hydride (NiMH) Batteries:
I don’t think I could define it better than wikipedia: “A nickel metal hydride battery, abbreviated NiMH, is a type of rechargeable battery similar to a nickel-cadmium (NiCd) battery but has a hydrogen-absorbing alloy for the anode instead of cadmium. Like in NiCd batteries, nickel is the cathode.”

Check out the full wikipedia entry on Nickel metal hydride batteries.

Nickel metal hydride (NiMH) advantages:

  • lighter than NiCad
  • 2-3X capacity to equal size NiCad
  • Nickel metal hydride (NiMH) disadvantages:

  • fewer life cycles compared to NiCad
  • shorter run time
  • performs the worst in cold temperatures
  • higher self-discharge level than NiCad
  • voltage drop at near-discharged levels
  • Nickel cadmium (NiCd) Batteries:
    According to Wikipedia: the “nickel-cadmium battery (commonly abbreviated NiCd and pronounced “nye-cad”) is a popular type of rechargeable battery for portable electronics and toys using the metals nickel (Ni) and cadmium (Cd) as the active chemicals.”

    Learn more about the Nickel-cadmium battery.

    Nickel cadmium (NiCad) advantages:

  • longer life cycles
  • performs in cold temperatures (perform well to 20F)
  • lower self-discharge level than NiMH
  • no voltage drop at near discharged levels
  • Nickel cadmium (NiCad) disadvantages:

  • Heavy
  • May suffer from “Memory Effect” or “False Bottom Effect” if constantly discharged half-way and then recharged
  • The Lithium ion (Li-Ion) Battery:
    The new comer to power tool batteries, Lithium Ion are hot because they have “one of the best energy-to-weight ratios, no memory effect and a slow loss of charge when not in use,” according to Wikipedia.

    Get the full story on Lithium ion (Li-Ion) Batteries.

    Lithium ion (Li-Ion) advantages:

  • High performance in cold weather – to 0F
  • Light
  • Increased life cycles over NiCad and NiMH
  • more rapid charge times
  • Lithium ion (Li-Ion) disadvantages:

  • less tested – in early stages of development
  • has shelf life based on life of battery, not related to charge
  • can erupt or explode in high heat – hot cars, direct sunlight, etc, or after tampering
  • permanent damage to battery if stored at too-low discharge level
  • Now you know what to look for – life cycles, run time, volts and Amp-Hours and you know the three major battery types. I hope that with that information you’ll be better equipped to make the decision between a NiCD, NiMH or Li-Ion battery!

    Here are some of the power tool battery resources I used in writing this answer:
    Battery Technology in the Power Tool World
    Rechargeable Battery Technicals
    Be sure also to read Battery Myths vs Battery Facts
    Will Lithium-Ion batteries power the new millennium?
    Building a Better Power-Tool Battery

    Regarding the second part of the question – which is best for charging with 220v power – I don’t know :) I will ask folks at WoodNet and FamilyWoodworking and see what they’ve found.