Battery types

There are many different types of batteries. You may be familiar with AA and AAA alkaline batteries, but there are also several different chemical types to choose from. When choosing your power tool, it’s important to consider the power capacity, weight, life cycle, and cost of these different technologies. Here are several of the most common batteries on the market:
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Lead-acid

This is one of the oldest battery technologies – it’s the type of battery widely used in cars to start the engine. Lead-acid batteries are rugged, shock resistant, and inexpensive, but they are also quite heavy, slow charging, and don’t have as much juice as other batteries of a similar size.

  • Power capacity: Low
  • Weight: Heavy (30 Watt hours / Kg)
  • Life cycle: ~800 charges
  • Cost: Inexpensive
  • Energy output: Very Low
  • Performance at low charge: Weak (erratic at low charges)
  • Self discharge rate: Low: Loses <0.3% of charge per day
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    Nickel Cadmium (Ni-Cd)

    These batteries are widely available and are one of the most common types found in battery operated tools. They are inexpensive, can be recharged many times, and deliver enough voltage to power high-drain electronics. They have one major drawback from other rechargeable batteries; if they are recharged after partial use, this can affect the batteries future capacity. The problem is called “memory” – as in, the battery seems to remember how much charge it had and resists charging above that point in the future. To avoid problems with memory, always make sure to completely drain Nickel Cadmium batteries before recharging them.

  • Power capacity: Medium
  • Weight: Medium (40-60 Watt hours / Kg)
  • Life cycle: ~1500 charges
  • Cost: Inexpensive
  • Energy output: Medium
  • Performance at low charge: Weak (tapers down gradually)
  • Self discharge rate: Medium: Loses 1% of charge per day
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    Nickel Metal Hydride (Ni-MH)

    Ni-MH Batteries

    These batteries are also widely available, and have many of the same strengths as NiCd batteries. They cost somewhat more than NiCd batteries, but do not suffer from the memory problem and have higher capacities. One area of concern is the high self-discharge rate: NiMH batteries lose energy quickly after charging, and it’s a good idea to top them off right before use.

  • Power capacity: High
  • Weight: Light (60-80 Watt hours / Kg)
  • Life cycle: ~1000 charges
  • Cost: Medium (some higher capacity models get expensive)
  • Energy output: High – appropriate for high-demand applications, such as camera flashbulbs
  • Performance at low charge: Strong (dies suddenly)
  • Self discharge rate: High: Loses 4% of charge per day
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    Lithium Ion (Li-Ion)

    These batteries were developed for cell phones and laptops – they have high power capacities, light weight, and extraordinarily low self-discharge rates. Unfortunately, they also cost a fortune and are in very short supply.

  • Power capacity: High – Very High
  • Weight: Ultra-Light (100+ Watt hours / Kg)
  • Life cycle: ~1200 charges
  • Cost: High
  • Energy output: High
  • Performance at low charge: Strong (usually gives a warning before dying)
  • Self discharge rate: Low: Loses <0.2% of charge per day
  • All of these batteries have strengths and weaknesses. For certain applications, a heavy battery with long life is superior, and for other uses, a light weight battery that can handle rapid drain is important. The better performing batteries almost always carry a higher price tag. Just remember that electric batteries purchase price is only part of the total cost. Compared to gas power tools, batteries offer reduced operating costs. Spending a little more upfront to get the most efficient designs can help your pocketbook for years down the road. This is also true with premium battery chargers – to get the most out of your battery system, you need an efficient battery charging system.

    Because they reduce pollution, electric tools and battery power are much
    better for the environment than small engines without pollution controls
    .

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