How to get the most from Li-Ion batteries

Six tips for getting the best possible life out of the Li-Ion batteries inside your smartphone, tablet or notebook.
Written by Adrian Kingsley-Hughes, Contributing Writer

I'm sitting at my desk and I'm surrounded by devices that owe their lifeblood to Li-Ion rechargeable batteries. And as most devices are now built in such a way that replacing the battery is tricky – if not almost impossible – so you want to get the best possible lifespan out of that battery.

Battery from the iPhone 5S
(Source: iFixit)

How much of a difference can taking care of the battery make? Well, I have both a second-generation iPod nano bought around December 2006 and a first-generation iPod touch bought in 2008 that are both still on their original batteries and are still going strong.

So, how do you get the most out of Li-Ion batteries?

Understand the "recharge cycle"

Every battery has a finite lifespan, and this is given as the "recharge cycle" or "battery cycle." Put simply, this is the number of charge/discharge cycles that a battery can endure before being no longer fit for service. Many manufacturers offer this number. For example, Apple state that the iPhone battery is designed to retain up to 80 percent of its original capacity at 500 full charge and discharge cycles, while the MacBook Pro or MacBook Air is designed to deliver up to 1000 full charge and discharge cycles before it reaches 80 percent of its original capacity.

But most people think that they can dodge this charge and discharge by topping up their battery regularly so the battery doesn't get fully discharged. Unfortunately, you "cannae change the laws of physics." If you only let you battery discharge by 25 percent, then doing this four times counts as a cycle. Same if you do five charges after 20 percent discharge, or even 20 recharges after 5 percent discharge.

You cannae change the laws of physics!

However, what you can do is take advantage of this. How? By hooking your device up to a power source when you can. For example, playing music from your iPod or iPhone at home via a dock, or plugging your MacBook into a power outlet when convenient.

In other words, don't put the battery through unnecessary cycles. Understand that I'm not saying keep the device on charge all the time – that would also be bad for the battery because it needs a regular workout to keep its internal chemistry in good condition – just be aware of wasting cycles.

Full discharge vs. Partial discharge

Some people say that you shouldn't allow a Li-Ion battery to become fully exhausted before recharging, other people say it doesn't matter.

Truth is, with Li-Ion batteries it doesn't really matter because their discharge is closely regulated by on-board circuits.

This used to matter with the old NiCd battery chemistry because they could discharge completely and become impossible to recharge (those batteries also didn't like being charged too often, and were much more sensitive to temperature), and it matters with lead-acid batteries which also don't take too well to being discharged too much unless they are rated for "deep cycle."

Use the right charger

I'm a big advocate in using the right charger for the right device.

It might be more convenient to pack one charger and a bunch of cables for trips, but for long-term usage you're better off using a charger designed for your device because that's delivering the right amount of power for the battery. Regularly using a charger that delivers too much or too little power will affect the longevity of the battery.

If you are going to go down the third-party charger road, then make sure they are a reputable brand. No-name junk might look and feel like an original charger, but based on my testing I've found that what comes out of the cable can vary wildly.

Does it really make sense to hook up a $500 tablet to a $2 charger? I think not. While battery protection circuits do a good job of shutting off power that could damage a battery, poor quality chargers can still damage devices and the batteries inside them.

Keep an eye on the temperature

See alsoKeeping your iPhone, iPad and MacBook running in the cold weather

Room temperature – around 20°C/70°F – is the best temperature to charge equipment at. However, since we don't all life in climate-controlled rooms, we can extend this range out to 5 to 45 °C/ 41 to 113 °F. Anything either side of this and things can get bad for the battery. This is especially true for charging the battery at temperatures below 0 °C/32 °F, which can permanent damage the battery.

Subjecting Li-Ion batteries to temperature extremes can also physically damage the battery, causing it to warp or crack. This, in turn, can damage the device containing the battery.

Avoid physical stress

Drops and falls can damage batteries, causing it to leak a cocktail of corrosive chemicals, all of which are bad for electronics.

Long-term storage

What should you do if you plan on storing your device for an extended period? The normal instinct is to full charge the device, but I've found that only charging it up partially – around 50 percent – is the best way. Storing a battery in the discharged state can push it to the point where it won't recharge, and storing a battery fully charged can shorten its life.

Long-term storage is best done as close to room temperature as possible. So avoid really cold rooms or keeping the device next to a radiator.

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