Answering Common Questions About Li-Ion Batteries

Posted by on February 1, 2011

Prolonging the life of your cordless tools includes prolonging the life of your batteries. While Li-Ion batteries are pretty advanced technology, there are still common mistakes and misconceptions that significantly reduce performance and battery life. Keeping a few simple principles in mind will help maximize the performance of your Li-Ion battery.*

Do not, do not, do not drain your Li-Ion battery to zero power. This not “maximizing run-time,” it’s permanently damaging the battery. Over-discharging will cause you to lose overall run-time and life cycle. (So for Pete’s sake, don’t tape the trigger down!) Instead, wait until your tool starts to perform sluggishly, then charge the battery back up to maximum capacity. If you’re pushing to meet a deadline, a spare battery can keep downtime to a minimum.

Over-charging is not a concern with most Lithium-Ion batteries. In fact, many manufacturers recommend you leave charged batteries in the charging station until you’re ready to use them. This is because most Li-Ion chargers feature technology that switches to “maintenance mode” when the battery is fully charged. This protects the battery cells from getting fried, and allows the battery to retain a full charge. (If the battery is stored out of the charger, it will slowly lose its charge over the next few days.)

Memory Effect
“Memory” was a common problem for Ni-Cad batteries. If a battery was used for repetitive, light application, that battery could develop a charge “memory.” This would seriously compromise a battery’s run-time. Fortunately, the technology behind the newer generation of Li-Ion batteries is not susceptible to this effect.

Extreme temperatures, either hot or cold, can affect a battery’s performance. If a battery gets too hot (above 105º F) or too cold (below 40º F) it will not fully charge. Attempting to charge batteries in these extreme temperatures can actually cause permanent damage and significantly affect run-time. To be safe, make sure you show up to the job site with fully charged batteries and recharge them when you get home.

Li-Ion batteries have a much lower discharge rate than Ni-Cad batteries. However, “low discharge” is not the same as “no discharge.” If a Li-Ion battery discharges to point of complete loss of charge, the effect is the same as over-discharging the battery during use: a permanent loss of capacity. If you have a few extra batteries sitting in a closet or workshop, make sure to periodically recharge them to full capacity. “Periodically” depends on the age of the battery: as the battery gets older, it will lose charge more quickly and thus need to be recharged more frequently.

While there are several internal safety devices to prevent such an occurrence, it is possible that a Li-Ion battery may rupture, ignite or combust if exposed to high temperatures. For this reason, batteries should be stored in cool temperatures, away from flammable materials.

* The information in this article was complied from a variety of manufacturers. While the information above does apply to Li-Ion batteries in general, you should consult each manufacturer’s guidelines regarding care for their particular line of Li-Ion batteries.

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