The Risks or Benefits of Charging Devices Overnight?

Many of us charge phones and laptops overnight but is this good for the battery and is it potentially dangerous, and how can we safely get the most from our device batteries?

Batteries

Smartphone and laptop batteries are Lithium-Ion (Li-Ion). These batteries have high energy density so they can be made small, while their rate of self-discharge is much lower than alternatives (like Ni-Cad for example) which means less charging, they have a high cell voltage, they don’t require priming (for a first charge), and there’s little or no maintenance required.  All these characteristics make them ideal as the power component in our essential, portable electric items.

That said, lithium batteries contain a flammable electrolyte which could be risky in some circumstances (remember the famous Samsung Galaxy Note 7 fires back in 2017?), they need protection (circuitry and special chips) to prevent them from being over-charged and discharged too far, they age (whether in use or not) so require replacing, and they are relatively expensive.

Likes and Dislikes

Knowing how to protect and get the best from the battery in your phone or laptop requires knowing a few basic conditions that batteries like and dislike.  For example:

Your battery generally likes:

– Partial charges that keep the battery between 20 and 80 percent.  This is because a battery degrades at its fastest rate if it is regularly charged past 80 per cent or when it drops below 20 percent. Devices seem to operate best when batteries are around the 50 per cent charge mark.

Your battery generally dislikes:

– Extremes.  This can be extremes of temperature below 32 Fahrenheit (0 Celsius) and above 158 Fahrenheit (70 Celsius) which can degrade the battery, let alone having an adverse effect on the device that the battery may be inside at the time.  This means avoiding leaving phones in warm sunlight (e.g. while sunbathing or sitting outdoors, or leaving the phone in a hot or cold car, perhaps overnight). Avoid the practice of putting phone batteries in fridges or freezers to ‘revive’ them.  Although there are positive accounts of this, it can result in degrading the battery. Charging devices in extreme temperature environments should also be avoided – room temperature is best.

– Being kept at 100 percent charge for long periods of time e.g., if charging at night.  This is when a battery can degrade the fastest.

– Apps being used while your device is charging. Using apps on your phone, for example, while the phone is still connected to the charger can heat and damage the battery and damage the device.

Overnight Charging

Overnight charging of phones and laptops frequently raises questions about efficiency, and safety.

Efficiency

Overnight is often a very convenient time to charge a phone or laptop but, since it only takes around an hour to charge a device, leaving it connected for 6 or 7 hours is not efficient. This is because phone or laptop batteries degrade fastest if left at 100 per cent for long periods of time (i.e. overnight), and a small ‘trickle charge’ is produced to compensate for any energy lost by the device.  This means that the battery is being unnecessarily used/over-used and switching to the mains power via the cable (when the battery is fully charged), could mean unnecessarily using electricity.

Safety

Although there are plenty of horror stories of phones catching fire while charging overnight, many of these appear to be where a phone has been left in a situation where there has been a lack of airflow and where it has been overheated (e.g. by being left under pillows or clothes). Generally, although not good for devices, overnight charging is relatively safe. Tips for making overnight charging as safe as possible include:

– Placing the device on protective/non-flammable surface, e.g. on a plate/saucer rather than on or under books, clothes, or on sofas.

– If possible and practical, take a phone out of the case when charging overnight.

– If you wake up in the night, unplug the devices to prevent constant trickle-charging or use a smart plug that’s on a schedule to turn off at a certain time when you’re sure the battery will have been charged.

Cables

Using high quality (preferably genuine and device compatible) chargers and cables which have correct safety marks (CE safety mark and output voltage that’s compatible with the device) can reduce the risk of fire and/or damage to the device and battery.

Replacement Batteries

Having a replacement battery fitted by a professional, as is often necessary with many new device models, is another way to avoid operational and safety problems.

Other Ways To Treat Device Batteries Well

– Other ways to maximise battery life, device efficiency and maintain safety include:

– Turn off unnecessary services on the device and use battery savers (often suggested by an on-screen prompt) to make the most of each charge.

– If a laptop must be left on overnight, remove the battery and use the adapter to power the laptop. This will put less of a burden on the battery by sending power directly to the laptop.

– Fully charge laptop batteries at least once a month to help the laptop to calibrate its estimator, i.e. to help it to accurately know how long the battery will last.

What Does This Mean For Your Business?

Mobile devices such as smartphones and laptops are now essential business tools. Although they tend to be regularly replaced, some knowledge of how batteries (and devices) perform best and getting into good habits as regards battery care can prevent batteries failing at important times, can improve safety, reduce costs (replacement batteries and electricity), and extend their life. Mobile and remote working has become essential for many businesses over the last year and with a surge in demand for laptops and phones fuelled by the pandemic, it is more important than ever that knowledge of how to maintain the batteries and devices is made available to improve efficiency and to keep remote workers safe as well as productive.