You're all familiar with the negative electrode half reaction equation, right? xLi+ + xe- + 6C <--> LixC6? Nursery school stuff, I’m sure. But rather than bore you with talk of gravimetric energy density (whatever the heck that means), in this feature we’ll use layman’s terms to explain how to get the most from your mobile battery.
Lithium ion, often abbreviated to Li ion (Li being lithium's chemical symbol), is now the most popular battery type in portable electronics. However, it’s a relatively new phenomenon. Initial experiments with lithium proved disastrous due to its propensity for pyrotechnics, but substituting lithium ions for lithium metal worked wonders. Sony commercialised the first lithium ion battery in 1991, and here we are 20 years later, with lithium batteries in everything from mobile phones to laptops.
Scientists are constantly working to improve lithium ion. New combinations of metals are introduced every six months or so, but the long-term effects obviously can’t be measured for several years. It’s a constantly evolving technology, with both pros and cons.
On the plus side for Li ion batteries, they have low loss of charge when not in use, and are light and safe. One unfortunate New Zealander might choose to disagree with me on that last point; his Nokia battery exploded and caught fire in the middle of the night (as detailed in this PC World article). However, to be fair to lithium ion, Nokia had already identified an issue with that particular model of battery. Exploding lithium ion batteries are definitely few and far between.
The main downside for lithium ion is its short lifespan, which is often only two to three years or 300-500 cycles. It’s also massively sensitive to heat. Exposing a lithium ion battery to temperatures of 40˚C for a year reduces its capacity to around 65%. As such, leaving your mobile in the car on a hot day is inadvisable.
Back on the pro side for lithium ion we have its lack of memory; plugging in when the battery is only partially discharged is absolutely fine. Full discharges aren’t necessary. On the contrary, they’re actually detrimental to the battery’s performance and should preferably only occur every 30-or-so cycles. Partial discharging with frequent recharging is the order of the day. If that’s not feasible, consider using a larger battery. If you do invest in a bigger lithium ion battery for your mobile phone, keep the old one as a backup. Ideally it should be charged to around 40% before storage and kept in a cool place, like your fridge (seriously). When you bring it out of storage, charge it to 100% before use.
There’s a lot of confusion over initial charge cycles and the need for priming lithium ion batteries. Contrary to popular belief, there’s no need to charge a new battery for, say, eight hours the first time you plug in. This is a relic from the era of nickel-based batteries. Yes, gone are the days when your shiny new mobile phone spent its first night tethered to your wall.
Chargers that claim to fast-charge your lithium ion battery are somewhat of a fallacy. Generally, it takes one hour to reach 70%, and a further two hours are required for ‘topping’.
As well as treating your lithium ion battery gently with partial discharges, there are a few things you can do on the phone side of things to maximise the available juice per cycle:
1. Turn off Wi-Fi. This is a big one. Keep Wi-Fi on 24/7 and you’ll regularly find yourself having to plug in. If you look at the list of available networks on your phone, you’ll see it refreshes every few seconds. It does this whether you’re sitting in your house with the same old networks available, or walking down the street where the networks are constantly changing. Whenever you’re not using Wi-Fi, turn it off.
2. Turn off 3G. 3G is another infamous juice-guzzler. Some – but not all – phones have the option to turn it off. For Android users, there’s a handy app called APNdroid that allows you to effectively manage your data connection.
3. Email polling. With some email clients, you have the option to manually set the email polling interval. The smaller the interval, the bigger the drain on your battery. It’s a particular waste when you’re sleeping; your phone repeatedly checks for email that would be better downloaded in a single batch come morning. If you don’t use email often, you could set it to check manually.