Power and management

How to Prolong Lithium-based Batteries

The lithium-ion battery works on ion movement between the positive and negative electrodes. In theory such a mechanism should work forever, but cycling, elevated temperature and aging decrease the performance over time. Since batteries are used in demanding environmental conditions, manufacturers take a conservative approach and specify the life of most Li-ion between 300 and 500 discharge/charge cycles.

Counting cycles is not conclusive because a discharge may vary in depth and there are no clearly defined standards of what constitutes a cycle. Read more about What Constitutes a Discharge Cycle?. In lieu of cycle count, some batteries in industrial instruments are date-stamped, but this method is not reliable either because it ignores environmental conditions. A battery may fail within the allotted time due to heavy use or unfavorable temperature conditions, but most quality packs will last considerably longer than what the stamp indicates.

The performance of a battery is measured in capacity, a leading health indicator. Internal resistance and self-discharge also play a role but with modern Li-ion these carry lower significance in predicting the end-of-battery-life. Figure 1 illustrates the capacity drop of 11 Li-polymer batteries that have been cycled at a Cadex laboratory. The 1500mAh pouch cells for smartphones were first charged at a current of 1500mA (1C) to 4.20V/cell and allowed to saturate to 0.05C (75mA) as part of the full charge procedure. The batteries were then discharged at 1500mA to 3.0V/cell, and the cycle was repeated.

(batteryuniversity.com n.d.)

 Simple Guidelines for Storing Batteries

Primary batteries store well. Alkaline and primary lithium batteries can be stored for 10 years with moderate loss capacity.

Remove battery from the equipment and store in a dry and cool place.

Avoid freezing. Batteries freeze more easily if in discharged state.

Charge lead acid before storing and monitor the voltage or specific gravity frequently; apply a boost if below 2.10V/cell or an SG below 1.225.

Nickel-based batteries can be stored for five years and longer, even at zero voltage; prime before use.

Lithium-ion must be stored in a charged state, ideally 40 percent. This assures that the battery will not drop below 2.50V/cell with self-discharge and fall asleep.

Discard Li-ion if the voltage has stayed below 2.00/V/cell for more than a week.

(batteryuniversity.com 2015)

(batteryorganizer.org 2015)

A. The LCD display. In fact, almost half the power in most laptops is used by the screen, which is why dimming your screen can save you a lot of battery life. Below is a list of the major power consumers on your laptop. This list also applies to desktop computers, other than the screen figure.

LCD: 43%

Chipset: 21%

Processor: 9%

Graphics: 8%

Hard Drive: 5%

Network: 4%

Other bits: 10%

Obviously different systems will vary based on their components, but this gives a rough idea of where that battery power goes.

(Savill 2009)

Conserving battery power

Windows 7

Ever run out of battery power in the middle of an important meeting or a long flight? Even with advances in technology, your laptop battery can last only so long on a single charge. The trick is to squeeze the most out of the power that's available.

If you have time to do only one thing...

Use the Power saver power plan to maximize your battery life. You can always return to this article later to try more power-saving tips. To choose the Power saver plan, open Power Options in Control Panel.

Chances are, you already have ways to make sure your laptop always has power. Maybe you carry an extra battery, or your power cord, so you can recharge your laptop when a power plug is handy. (Always consult your manufacturer's instructions for the best way to recharge your battery.)

When those strategies fail, here are some other ways to help stretch your computer's battery life.

Choose a power plan that saves power

A power plan is a collection of hardware and system settings that control how your laptop manages power. Windows 7 has two default plans:

Balanced. Offers full performance and display brightness when you need it, but conserves power when the computer is idle.

Power saver. The best choice for extending battery life. The cost? Slower performance and lower display brightness.

Your computer manufacturer might offer additional plans.

To change your power plan

You can also create your own custom power saver plans. For more information, see Change, create, or delete a power plan (scheme).

Reduce display brightness

The display can use more power than any other part of a computer—even more than a hard disk and CPU. Some laptops have a dedicated button or dial to change the display brightness. To find out if your laptop has something like this, check the information that came with your computer or go to the manufacturer's website. You can also adjust the display brightness from Power Options in Control Panel.

Shorten the length of time before Windows dims and turns off the display

When you're not using the laptop—even for brief periods of time—you can save power by having Windows dim and then turn off the display after a period of inactivity.

To choose when Windows dims and turns off the display

Turn off or remove devices that you aren't using

Many USB devices use power just by being connected. If you use a USB mouse, you can save power by disconnecting the mouse and by using a touch pad or tablet pen. If you use a USB flash drive, unplug it when you're not using it.

Turn off PC cards and integrated wireless devices

These devices also use power. If you don't need them, turn them off.

(Microsoft 2015)

 What's the difference between sleep, hibernate, and hybrid sleep?

Sleep is a power-saving state that allows a computer to quickly resume full-power operation (typically within several seconds) when you want to start working again. Putting your computer into the sleep state is like pausing a DVD player—the computer immediately stops what it’s doing and is ready to start again when you want to resume working.

Hibernation is a power-saving state designed primarily for laptops. While sleep puts your work and settings in memory and draws a small amount of power, hibernation puts your open documents and programs on your hard disk, and then turns off your computer. Of all the power-saving states in Windows, hibernation uses the least amount of power. On a laptop, use hibernation when you know that you won't use your laptop for an extended period and won't have an opportunity to charge the battery during that time.

Hybrid sleep is designed primarily for desktop computers. Hybrid sleep is a combination of sleep and hibernate—it puts any open documents and programs in memory and on your hard disk, and then puts your computer into a low-power state so that you can quickly resume your work. That way, if a power failure occurs, Windows can restore your work from your hard disk. When hybrid sleep is turned on, putting your computer into sleep automatically puts your computer into hybrid sleep. Hybrid sleep is typically turned on by default on desktop computers.

(Microsoft 2015)