BU-808c: What the User Can Do

Tweak battery care with simple user changes.

Environmental conditions, and not cycling alone, govern the longevity of lithium-ion batteries. The worst situation is keeping a fully charged battery at elevated temperatures. Battery packs do not die suddenly but the runtime gradually shortens as the capacity fades and the self-discharge increases.

Lower charge voltages prolong battery life but this also reduces the runtime. Industrial uses, such as EVs and satellites, take advantage of this to extend the battery service life but it increases battery cost and adds to weight. Similar provisions to prolog battery life are often also available on portable communications and computing devices, but these are seldom used. Consumers demand nothing but maximum runtime; planned obsolescence solves most battery problems.

One such adjustment to prolog the life of a laptop battery is lowering the charge voltage when connected to the AC grid. To make this feature user-friendly, the device manufacturer should offer the “Long Life” mode that keeps the battery at, say, 4.05V/cell, resulting in a capacity of about 80 percent. Before traveling, the user would command the “Full Capacity” mode to bring the charge back up to 4.20V/cell. The saturation charge would take about an hour and fill the battery to 100 percent capacity.

The question is often asked: “Should I disconnect my laptop from the power grid when not in use? Under normal circumstances this should not be necessary because once the lithium-ion battery is full, a correctly functioning charger will discontinue the charge and topping charge will only engage when the battery voltage drops to a low level. Most users do not remove the AC power, and this practice is safe.

Heat buildup is less of a concern with modern laptops than in the past and reported fires are fewer. What remains valid is keeping the devices cool when running them in bed or on a pillow that may restrict the airflow. Not only will heat stress electronic components, elevated temperature causes the electrodes in the battery to react with the electrolyte and this will permanently lower the capacity.

High-energy Li-ion should be charged at less than 1C. Avoid so-called ultra-fast chargers that claim to fully charge Li-ion in less than one hour.

Granted, everyone wants to keep the battery as long as possible but everyday stresses cannot always be avoided. Device manufacturers should choose a battery that can live up to reasonable stresses and still deliver the anticipated life span. As a doctor cannot predict how long a person will live based on diet and activity alone, so also does the life of a battery vary, and it can be cut short by an unexpected failure. In this respect, batteries and humans share the same volatility.

Last updated 2016-01-20

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On September 25, 2016 at 9:01pm
Feaver wrote:

Thank you for that article!
I read a lot information now but still have one specific question, whichh I haven’t found an answer for yet.
I understand the answer to “Should I disconnect my smartphone/laptop from the power grid when not in use?”, however, what about “Should I disconnect my laptop from the power grid WHILE in use?” for example at the office or at home.
a) Keep my laptop/smartphone (in my case surface pro 4, so taking battery out is not possible) plugged in
b) Prolong battery life by using it until XX%? and charge it again to YY%?”
If b) please also tell us the XX and YY percentages.
Thanks a lot!

On January 27, 2017 at 6:25am
Jonas wrote:

I was wondering the same thing… “Should I disconnect my laptop from the power grid WHILE in use?” for example at the office or at home.