Recently, a customer deploying one of our emergency evacuation systems asked us the following question:

“What is the best way to store our handhelds and tablets to maximize their battery life?”

We wish we could have given this customer a simple answer, but unfortunately, there are many considerations which must be taken into account. As we gathered information for this client, we decided to put together an article to provide as a resource for the community.

About Lithium-Ion Batteries

In the past 10 years, lithium-ion technology has become the gold standard in the battery industry. Designed to be lightweight, long lasting and easily rechargeable, lithium-ion batteries are perfect for use in mobile devices. In addition, lithium-ion batteries are able to maintain their charge when stored for extended periods of time, whereas previous battery technologies would lose charge over the course of a few days. In an era where cell phones and laptops continue to get smaller, more powerful and lighter weight, mobile electronics manufacturers are turning to lithium-ion as their preferred power source.

With proper use, lithium-ion batteries will last up to 300 full charge cycles. After these cycles, their charge capacity is reduced by approximately 20% and battery life will start to degrade rapidly. A charge cycle is defined as a full discharge to a full charge, which can be made up of multiple partial discharges (i.e. four 25% discharge cycles = 1 full discharge cycle). So, how long should you expect your lithium-ion battery to perform at its optimal level? Here is a simple answer:

If a battery is fully discharged and recharged every day, it will last about one year.

This explains why people who use their laptops heavily, often need to replace their batteries frequently. Additionally, battery life for lithium-ion batteries is compromised because they are installed in mobile devices. Physical impacts, vibrations, and variances in temperature cause damage to the battery and shorten the battery’s operational life.

What Can I do to Extend the Life of my Lithium-Ion Battery?

Here are a variety of practices you can carry out to help extend the life and length of charge on your lithium-ion powered handheld, laptop, or smartphone:

• Before first use, apply a full charge to your device. Typically lithium-ion devices are pre-charged to about 50% capacity.

• Lithium-ion batteries do not need a full discharge and recharge to maintain their battery life. In fact, smaller discharges are better.

• Do not allow the battery to be fully discharged for more than one day.

• Do not allow fully charged batteries to sit for extended periods of time (months). If batteries must be stored, store at a 40% charge to prevent loss of capacity.

• When storing for long periods of time, apply a discharge/charge once every 1-3 months.

• Avoid physical impact as this will affect the overall integrity of the battery.

• Avoid temperatures below freezing or above 122 degrees Fahrenheit. For both high and low temperatures, the further the operating temperature is from room temperature the faster the battery degrades.

  

• Lithium-ion batteries are prone to overheating, so provide proper ventilation for your device. Ironically, one of the worst things for your laptop is working with it on your lap for an extended period of time. The heat of the battery plus your body temperature can cause your device to overheat. Use on a table or lap table will allow the heat to better dissipate.

The advice we ultimately provided our client was this rule of thumb; lithium-ion batteries should be replaced at a minimum of once every 18 months and optimally every year. This will ensure your lithium-ion powered device will provide you with a duration of operation that will meet your expectations and requirements.

By: Mark Miller