Battery Power

Today’s battery powered tools are a far cry from the feeble battery powered tools of ten years ago.  With voltages up to 28 there is plenty of power for a job without the hassle of dragging around a cord.

But are battery powered tools hassle free?  Definitely not.  They have limited life spans, are affected by temperature and cost money to replace. It helps to understand the differences between the various battery technologies, the advantages and disadvantages of higher voltages, and what might be considered the best way to take care of your batteries.

As always: Read the manufacturers directions and follow their advice to get the most out of your tools and batteries.

Voltage and Current

Batteries are rated by voltage and capacity.  Some typical voltages are 9.6v, 14.4v, and 18v.  The greater the voltage the more power can be delivered by the battery. Higher voltages allow the battery to deliver more raw power to the hungry tool.  Although many factors determine the total life of any battery, generally a higher battery voltage means fewer charges.

Typical recharges:

• 9.6v about 1000-1200 recharges
• 14.4v about 700-900 recharges
• 18v about 500-800 recharges

Capacity is measured in amperage (amp) hours (e.g. 1.2 amp hours, 2.0 amp hours, 2.4 amp hour).  This rating indicates the amount of current that can be delivered in one hour on a single charge.  A 2.4 amp hour battery can deliver 2.4 amps of power for 1 hour, or 1.2 amps for 2 hours, etc.  The larger the capacity of the battery, the longer it will be able to deliver useful power to the tool.

Common Battery Technologies

Today's tools use one of these three major battery technologies, each with it’s pros and cons.  NiCad has been around a long time and is tried and true.  However, as Li-Ion chemistries improve, it appears to be the emerging technology of choice with a significant energy to weight advantage over the other battery types.

Chargers

Every charger is designed for a specific type (or types) of battery.  Don’t try to mix chargers and batteries which don’t belong together.

Most chargers today do ‘fast charging’, recharging a drained battery in an hour or less.  They have sensors to detect when the battery has reached a fully charged state to prevent overcharging and are designed to sense the battery temperature and to stop charging if the battery is hot. Some batteries function better if they are balance, or topped off via trickle charging.  This is performed after the battery is charged, but while it sits in the charger which is why some manufacturers recommend leaving a battery in the charger overnight occasionally.

A good charger shouldn't overheat or overcharge a battery, but sometimes they do. Our experience with NiCads shows that leaving the battery in the charger can cause premature battery failure.  We use a simple timer that we set when we drop a battery in the charger.  This keeps us from inadvertently leaving a battery charging for extended periods of time. The downside is that if we go on vacation for a month, we come back to a dead battery.

Remember to keep the contacts on the charger clean for the best performance.

Temperature and Battery Performance

Heat is the killer of batteries

Heat destroys batteries.
Batteries will heat up under normal use.
Keep batteries in the shade, hot batteries have less storage capacity.
Don’t over stress a tool.
Today’s chargers measure the temperature of a battery and allow it to cool before charging.

Cold reduces power delivery

Cold won’t hurt batteries, but it will reduce the amount of power the battery can deliver.  Batteries should be near room temperature for optimal charging. NiCad batteries can potentially deliver power down to -20F. LiIon and NiMH down to about 0F. Some chargers will warm up batteries for use and to allow optimal charging.

Best practice

• Don’t – Get things wet.  Getting batteries wet can cause internal shorts, destroying the battery.
• Don’t – Overstress a tool.  The tools and batteries will get hot during normal use.  However continuously over stressing a tool will overheat batteries and reduce their life.
• Don’t – Run a tool until the battery has nothing left.  Stop using the tool as soon as the power beings to diminish and recharge.
• Don’t – Try to drain batteries in a tool to full discharge to extend the life.  If batteries have too low a voltage, they can reverse voltage and never recover.
• Don’t – Leave the batteries in the charger for weeks at a time.  Constant topping off of the batteries can reduce their life.
• Don’t – Leave the batteries exposed to high heat such as in an enclosed car in the summer.  Heat will reduce the batteries life.  Especially if hot batteries are then put under heavy load.

• Do - Run the tool until it begins to loose power, then recharge the battery.
• Do – Recharge unused batteries every few months since they loose their charge over time.
• Do – Remove the batteries from the charge after the charge is complete.
• Do – Occasionally leave the batteries in the charger overnight to top off and balance the cells.  We have our chargers on a 1-8 hour timer, which we set when we drop our batteries in the chargers.
• Do – Let batteries cool after use, before charging.  Many of today’s chargers will measure the battery temperature and only begin recharging when the battery has cooled down.
• Do – Keep the contacts on the battery, tools and chargers clean.
• Do – Read and follow the manufacturers instructions.  Although we have tried to gather generally good advice on battery care and maintenance, every battery and charger combination is different.

Please recycle

Rechargeable batteries should be recycled to keep our landfills from being contaminated by toxic materials. Many manufacturers have recycling programs. Also, most Home Depots, Lowes, Radio Shacks and many others, have recycling containers on site. Go to www.rbrc.org to find a recycling drop off location near you.