Recently, rechargeable lithium-ion batteries used in consumer applications have received attention because some have melted or even exploded. But, contrary to sensational news reports, lithium-ion batteries remain safe and engineers will continue to design them into portable equipment.

The nature of the Polymer Lithium ion Battery chemistries produces high amounts of electricity with light-weight materials, so lithium-ion batteries generally provide the best power sources for portable electronic devices. And, continuing research into lithium-ion and lithium-polymer chemistries and materials will increase the capabilities of these batteries for some time.

But, do not expect to find bare lithium-ion cells on your distributor's shelf. Reputable cell manufacturers sell only to qualified and authorized companies that place these cells in battery packs. Those packs include electronics that protect users and batteries. When a design calls for a lifepo4 battery, plan to work with an authorized company that can tailor a battery pack to your requirements.

Safety looms large in the realm of lithium-ion batteries, so battery-pack suppliers include internal circuits to control how the batteries charge and discharge and to monitor operating conditions. Lithium-ion battery packs include internal positive-temperature-coefficient devices, thermal fuses and electronic circuits that ensure the packs operate only under specific conditions.

Most of the electronic safety circuits keep a battery pack's voltage and current within design limits. If the pack experiences a voltage surge due to a bad charger, the internal circuit disconnects the charger from the battery pack.

Safety circuits assume people will do something wrong, such as try to over-charge a pack or connect it to the wrong charger. In these cases, the safety 18650 battery circuits can stop the charge, temporarily reset the charger or blow a fuse to stop charging completely and prevent anyone from using the battery pack again.