Discover simple tricks to lower power consumption and extend runtime.
As the author of BatteryUniversity.com, I get many interesting enquiries from battery users. A man writes, “Hi, I am looking for an answer to a perplexing question. A co-worker and I have identical cell phones from the same provider. Moving into a new house, she complained of short battery runtime. I told her she was out of her mind, but then I noticed my battery behaving differently when I travel. Is there some mysterious force that’s draining the battery?”
Yes, there is a hidden force that drains the battery but it’s not mystical. When a cell phone is in constant communication with the tower, it transmits small bursts of power once every second or so to check for incoming calls. To save energy, the signal strength adjusts the transmission power and only consumes what is needed to maintain communication. If the cell phone is close to a repeater tower, the energy required to communicate is very low. Moving farther away or entering an area with high electrical noise, such as a shopping mall, hospital or factory, and the required energy increases. An analogy is sitting in a restaurant. When the surroundings are quiet, the voices are kept low and as the crowd grows everyone needs to talk a bit louder.
Living in sight of a tower has advantages and your battery will last longer between charges. Where you park your mobile phone in the house also affects runtime. A manager of a large cellular provider in the UK said his son experienced shorter standby times after moving from the upstairs bedroom to the basement. If possible, leave your mobile phone in an upstairs room facing a tower. When traveling by car place it near a window rather than on the floor but avoid direct exposure to the sun.
Similar rules apply to TETRA and P25 radio systems, cordless telephones, Wi-Fi and Bluetooth devices. A wireless headset that communicates with the cell phone from belt to ear provides longer runtimes than when placing the handset on the dining-room table while cooking in the kitchen. Although the quality of communication stays the same, the Bluetooth headset needs to work harder when placed farther away from the user.
The energy savings only apply when the wireless device is in the “on” position. When “off,” the load on the battery is very low and only provides power for housekeeping functions such as maintaining the clock and monitoring key commands. Housekeeping and self-discharge consume 5 to 10 percent of the available battery energy per month.
Laptop batteries fare badly in terms of life span. Laptops are demanding bosses that request a steady stream of power under poor working conditions, toiling in a warm climate. In addition, the battery is exposed to a high voltage when connected to the AC main. Warm temperature and full state-of-charge are the cause of short battery life in laptops, not cycling.
Modern laptops run cooler, so do tablets and smartphones that now share the laptop market. To provide reasonable runtimes on these devices, the battery size has more the doubled compared to a cell phone. Although reduced in energy consumption, a few power-hungry components remain and these are the prosessor, display and transmitter.
Following the advancements made in laptops, improving the specific energy of the batteries is being offset by added features. A survey conducted on laptops indicated that given the option of a larger size with added weight, most users settled for what was offered. This may also apply to smartphones and tablets. For better or worse, we learn to live with what we have.
Simple Guidelines to Prolong Lithium-ion Batteries
Last Updated 2015-04-29
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