Choosing the Right Battery Type When Buying Cordless Power Tools

Choosing the right battery type when purchasing a new cordless power tool can be a bit confusing. It’s important to understand what your needs are before making a purchase, as different battery types can add significant costs to your tool purchase. There are a few terms and characteristics of rechargeable batteries that all buyer’s need to understand to make a smart buy. These characteristics directly affect the overall life and run time which should be considered prior to purchasing. These characteristics are defined as follows:

Rechargeable Battery Characteristics

1. Cycle Life – The overall life of a battery is typically expressed in the number of charge cycles it can withstand before completely losing its capacity to charge.

2. Self-Discharge – This is were the rechargeable battery slowly loses its charge over a certain amount of time. For heavily used cordless power tools this usually is not a problem, but when a tool is stored for long periods of time the batteries self-discharge can be a problem. There is nothing more frustrating than grabbing a tool to work on a project only to find there is no power.

3. Voltage – Voltage determines the amount of power the battery will output. This means the more voltage a battery has, the more power output of the tool. Matching the voltage to the workload has a typical scale as follows: Light Workload: 7v – 15v, Medium Workload: 12v – 18v, Heavy Workload: 18v – 24v.

4. Capacity (run time) – This is the amount of time a battery can power its tool between charges. A batteries capacity is determined by the amount of amperage hours (Ah) that it can deliver.

5. Deep Discharge – The deep discharge of a battery is when the tool battery looses its complete charge during normal usage of the tool. Deep discharge can be a major problem for some batteries and can result in a reduction of a battery’s life cycle and capacity.

6. Memory Effect – Memory effect can occur when a battery is charged over and over without being allowed to fully drained. The effect is when the battery remembers how much it has been recharged and adopts a shorter charge range.

Cordless Power Tool Battery Types

There are three types of rechargeable battery types used by most major cordless power tool manufacturers. These three types are Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMH), and Lithium Ion (Li-ion). Below is an overview of each of the different rechargeable battery types.

Cordless Power Tool Battery Types

1. Nickel Cadmium

The Nickel Cadmium batteries have a long cycle life and are the oldest design of rechargeable batteries. These batteries are low cost and durable, but they typically underperform when compared to the NiMH and Li-ion batteries. NiCd batteries are heavier than the other two batteries and they have a lower capacity. These batteries must be deep discharged at least once a month or they will develop a severe memory effect.

NiCd Battery Overview:

    • Cycle life – 1000+ Charges
    • Self-Discharge – 15% – 20%
    • Capacity – 1.2 Ah – 2.2 Ah
    • Charge Time – Fast
    • Maintenance – Deep discharge once a month
    • Memory Effect – High if not properly maintained

2. Nickel Metal Hydride

NiMH batteries improve upon the Nickel Cadmium batteries in several ways. These batteries are lighter, less toxic to the environment, and can have 2 to 3 times the capacity of a NiCd battery. These batteries are typically cheaper than Li-Ion batteries and when stored properly the NiMH battery’s cycle life can be significantly increased. A lack of use and deep discharge can damage these batteries and they are more sensitive to temperature. NiMH batteries need to be stored in a temperature range of 33 to 103 degrees.

NiMH Battery Overview:

    • Cycle life – 1000+ Charges
    • Self-Discharge – 20% – 30%
    • Capacity – 2.2Ah – 3.0 Ah
    • Charge Time – Fast
    • Maintenance – Deep discharge once every three months
    • Memory Effect – Moderate if not properly maintained

3. Lithium Ion

These batteries are a relatively new technology to be introduced to cordless power tools. These batteries outperform all other options, but they are more expensive. These batteries do not suffer from memory effect, but they are susceptible to heat damage. While Li-ion batteries do not wear out over time due to charging issues, age and use will wear out these batteries over time. The Li-ion battery is the best choice for cordless power tools as they charge fast and have a higher capacity.

Li-Ion Battery Overview:

    • Cycle Life – 300 – 500 charges
    • Self-Discharge – Very slow
    • Capacity – 3.0 Ah+
    • Charge Time – Moderate
    • Maintenance – None
    • Memory Effect – None

The overall life cycle and capacity are the primary factors when choosing the right rechargeable battery type for your cordless power tool. Depending upon your needs, you can choose the right battery type and save money on your purchase by following these guidelines.