Manufacturers and technology have come a long way in the development of cordless tool batteries.  With batteries being such an important part of the cordless power tool, I decided to dedicate some time and explain some information on batteries.  Cordless tools use three type of batteries.

Types of Batteries

Nickel Cadmium (NiCad) – This was the battery that started it all.  NiCad is the oldest and most reliable battery.  NiCad stands the test of time so far.  They have a high recharge cycle life, meaning they can be recharged over and over, longer than the NiMH.  They are not as temperature sensitive as the NiMH, which means you can use them in cold or hot weather.  NiCad is cheaper than NiMH.   NiCad batteries tend to be more harmful to the environment when disposed of, that’s why you see companies such as Dewalt sell NiCad in the states and NiMH in some European countries.  Some European governments put heavy taxes on NiCad, so the companies will not sell the batteries. 

Bosch has produced the new line of NiCad called Blue Core Technology.  According to Bosch, this adds 50% more to the battery life while allowing the user to recharge the battery in 30 minutes instead of 60 minutes.  Bosch created rods inside the battery that cool the battery as it charges, allowing a quicker charge.

Nickel Metal Hydride (NiMH) – NiMH is a newer battery that manufacturers have started to experiment with.  In terms of run time and amps, they have a slight advantage by going up to 3 amps while the NiCad is 2.4 amps.  Because they can have more Amps, they have a longer run time than the NiCad.  Another key advantage to NiMH is they are lighter than the NiCad.  The NiMH has downsides such as they are very temperature sensitive. They will not work below 32 degrees Fahrenheit and degrade quickly with temperatures above 105 degrees.  NiMH have a shorter battery recharge life.  Which means you basically have to buy two batteries for every one NiCad battery.  Manufacturers argue that because they have longer run time between charges, they basically have the same total work hours as the NiCad.  Currently this type of battery seems below grade for cordless, but some manufactures think in time with better technology, they will be able to get more use and better results with the NiMH.

Lithium Ion (Li-Ion) – Newer technology (used in cell phones, cameras and other small electronics) cost more, but offers longer run time, lighter weight and are not temperature sensitive.  Actually, the Li-Ion cell are cheaper than the NiCad, but because NiCad is in such demand and are produced more, NiCad can be sold for a cheaper price.  The V28 by Milwaukee weighs about the same as the 18 NiCad battery.  The Milwaukee V28 delivers the same power with the first pull of the trigger as the last.  NiCad continuously loses power as you use the tool.  Li-Ion are the best in cold weather and will still run at 0 degrees.  That is only if they are warm before they run.  Lithium Ion batteries still have a problem if you leave them out in the cold over night and try to use them.  Since all battery cells are linked together, a battery is only as strong as its weakest link.  Li-Ion offers the best protection.  There is a circuit that balances the the cells when in use and charging.  This balance makes sure all the cells are working as a team, and one not harder than another.  This will help even the wear and provide longer use.  However, the circuit actually presents one downside.  NiCad and NiMH can cool their tools through the tools design, while Li-Ion is dependant on the circuit.

*** You should know that there are three types of Lithium Ion batteries, so if you see a big price difference between two types of Lithium Ion this might be the reason.  The three types are: Cobalt,  Manganese and Phosphate.  You can read more about Lithium Ion Batteries Here.

Battery Myths


  • More volts and amps in the battery means the power tool is stronger and better.

False, Actually the motor, transmission and other components that produce the power also have a great effect on the tool’s performance, along with the quality of the magnets in the motor, metal gears, and the chuck that transfers to the bit.  Basically it is everything from the battery to the blade or bit, to how efficient it can transfer the power.

  • A charger is a charger

Actually some chargers keep charging even when the battery is fully charged.  This causes excess heat build up and decreases your battery life.  Most professional power tool battery chargers will shut off.  This means once the battery is fully charged, the charger will not try to push current through the batteries to charge it.

  • Batteries have a memory

This is false, but it use to be true.  Back in the 80’s when battery technology was just getting started, a battery did have memory.  Now-a-days with new technology, manufacturers have developed batteries with no memory.  So currently this is a myth.  Draining a battery all the way will actually cause more harm to the battery than good.  When you drain a battery all the way, you can actually damage cells and they will no longer hold a charge. Consequently, you might only be using 11 cells instead of all 12 cells. This lowers your power and battery life.  The best gauge to recharging your battery is to charge the battery when it can no longer function for the job.  If the saw starts to die when cutting, then it is time to charge it.

  • Keep Batteries in the freezer

Sounds goofy, but I have seen contractors bring a cooler with ice packs to the jobsites.  This will not help your power tool batteries.  Actually, the cold can hurt your batteries if your try to charge them.  NiCads are very durable batteries and will work in all most any environment.  If it is too cold for you to work outside, then just bring your batteries in with you and the batteries will be fine.

  • Batteries can be rebuilt


Some people say yes and some no.  I have read a lot about this and still get both answers.  The best thing to do is take them to a store and recycle them.  Battery prices are coming down, not to mention If someone rebuilds the battery, who knows if they did a good job or used recycled cells.  My best advise is spend a couple of extra bucks and buy the new factory batteries.

Battery Tips


  • NiCad and Li-Ion are extremely durable for heat and cold weather.
  • Consider what the tool will be used for.  Volts help, but it is not everything.  The tool is just as important.
  • Heat hurts batteries.  Normal heat from use is OK, but don’t do anything to create more heat.
  • Do not completely drain the battery, they do not have memory.  Charge the battery when it no longer performs its duty to its fullest capacity.
  • Keep your battery in a charger, a professional charger will keep your battery fully charged without putting strain on the battery.
  • Do not leave Lithium Ion batteries in cold places, as they will not operate at peak performance.

Helpful Terms

  • Cycle Life – The number of times a battery can be charged and discharged. 
  • Total Working Hours – The raw number of hours a battery will work before it will not accept a charge.
  • Amp Hours – Energy hold or gas tank.  Higher amps is a bigger tank and will run longer.
  • Volts – Horsepower, the more volts the more work.