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  • Hand plugging a charging cable into smart phone

    The Cost of Charging Your Mobile



July 2019


Do you charge up your mobile once a day? Leave it charging overnight? Whatever your charging habits, read on to find out just how much it’s costing you in energy.

Firstly, the good news. Charging your mobile phone is not very high on the list of energy-guzzling activities around your home. In fact, it’s extremely low. You’re looking at around $2.00 per year to fully charge your phone every day – much less if you have a smaller smartphone.

Given that the cost of charging your mobile battery isn’t going to break the bank, your biggest concern should be preserving battery life.

What’s the best way to charge my phone?

Mobile phones use lithium-ion (or li-on) batteries that are designed for fast charging. In fact, they like a little bit of charge, whenever you can. This is called “partial charging” – plugging your phone in or resting it atop its wireless charger for short spurts during the day.

The sweet spot for battery capacity is between 65% and 75% charge.1 If you can keep it in this zone by partial charging, the battery will generally last longer.

Should I let my mobile phone battery run down?

How low should you go before plugging your phone back in? The general advice for mobile phone batteries is to recharge sooner rather than later. Don’t wait until you’re in that ‘low power mode’ zone or, worse, nudging 0% battery charge.

It’s recommended to recharge when your battery reaches around 35% of its capacity.2 By recharging sooner, you can help to preserve the capacity of your battery for longer.

What’s more, if the battery is getting close to zero, then it’s recommended not to recharge all the way back up to 100% in one go as this can impact battery life.1

What happens if I overcharge my phone?

Mobile phone batteries are designed so that you can’t overcharge them. So what happens when you leave your phone plugged in overnight?

Today’s smartphones have a clever little feature that will cut off the supply of current once the battery is full. So, once your phone’s battery reaches 100% charge, it stops drawing electricity and cannot be overcharged.

However, during the night, your phone will sit there doing any background tasks that it’s programmed to do. Each time the battery dips below 100%, another little injection of electricity will boost it back up. Over time, this continual topping up can wear down your battery’s capacity.

To help preserve the life of your battery, it could be better to charge your phone before bedtime and then switch it off – or at least to aeroplane mode, if you need the alarm – before bed.

The final word

While the cost of charging your phone isn’t high, the cost of replacing a battery or phone is. Little changes to your phone charging habits could help to preserve the life of your smartphone battery.


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