How To Make Your Notebook Batteries Last Longer

Everyone wants to make their batteries last longer, both in terms of runtime powering our mobile equipment as well as charge-discharge cycle counts. There’s lots of information out on the Internet, but there’s just as much misinformation. Here’s my compilation of information from various sources to help you squeeze the most juice out of your notebook batteries.

I cannot possibly cover all kinds of notebooks and all sorts of batteries. So let’s just limit our scope to the most common configurations.  Most notebooks nowadays use Lithium-Ion (or Li-Ion) batteries, and that’s just what we’re going to focus on.

Li-Ion batteries generally provide about 300-500 charge/discharge cycles. What counts as a “cycle”? If you start off with 100% capacity, then discharge till 0%, then recharge back to 100%, that counts as 1 cycle. If you start off at 100% capacity, discharge down to 80% then you recharge again to 100%, you can repeat this 4 more times before it counts as 1 cycle. Yes, that’s 1 cycle and not 5 cycles.

Li-Ion batteries have a life-span of about 2 to 3 years. It does not matter whether or not the batteries are actually being used. The aging results in permanent storage capacity loss. The speed at which Li-Ion batteries age is determined by temperature and stored charge level. The worst condition is to keep a fully charged battery at elevated temperatures, which is what happens when you leave a battery in a running notebook that is mostly connected to a power adapter.

If you need to store your battery for a long time, the ideal condition is to keep it at 40% charge level and at close to 0 degrees celsius. (Of course if you find it awkward to keep your batteries in a refrigerator, then just store them in a nice cool place. Never store batteries in a freezer.) Li-Ion batteries continue to age even if they are not in use. So, unless you actually plan on using them, don’t buy multiple batteries at one go.

With Li-Ion batteries, you do not need to discharge the battery fully before you recharge it. You can recharge it any time you want. It is actually more stressful for the battery to be fully discharged and then recharged.

You may have heard of the term “memory effect”. This is a condition that affects Nickel-Cadmium batteries. These batteries tend to remember the amount of energy drawn on preceding discharges, and subsequently they think that’s the maximum capacity they have and rapidly drop the voltage when discharged beyond that capacity. In simple terms, it means if you discharge a Nickel-Cadmium battery partially and recharge them again, the battery appears to run shorter and shorter. Li-Ion batteries do not have this problem, so you don’t have to worry about it, nor do you need to be concerned about when you should or shouldn’t recharge your Li-Ion batteries.

The only reason why you might want to fully discharge your Li-Ion battery may be to do with battery calibration. Calibrating the battery helps your notebook accurately determine the charge level and run time remaining when on battery mode.

This Apple’s official information for calibrating all models of MacBooks:

1. Start off by charging your notebook battery until it is fully charged.
2. Keep the battery fully charged for at least two hours. You can still use the notebook, just make sure that the power adapter is plugged in.
3. Disconnect the power adapter and let the battery discharge. You can use the notebook during this time. When the battery gets low, you will get the usual battery low warning.
4. Just keep using your computer until the notebook forcibly goes to sleep. Of course, you might want to save your important work first before the battery gets terribly low.
5. Leave the notebook in sleep state for at least five hours.
6. Reconnect the power adapter and charge the battery until it is full again.

Calibration does not increase the battery life (be it run time or cycle count). However, you should not calibrate your battery too often. The recommendation seems to be about once every 30 discharge cycles.

There is actually a little caveat with the charge-anytime recommendation. Although it is fine to charge Li-Ion batteries any time without having to fully discharge them, it is actually not good to charge them when they are nearly full. In fact, some batteries (such as in the MacBooks and MacBook Pros) already have built-in circuitry to prevent charging when they are almost full. You need to discharge a battery from 100% down to 95% or thereabouts before they will charge again.

In summary, these are the battery usage guidelines you should follow:

1. Use the battery normally. If you can charge it, then charge it.
2. If you plan to connect your notebook to the power adapter for long periods of time, remove the battery.
3. Once a while, like maybe every 30 cycles, do a full discharge/recharge.

There are also some don’ts to take note of:

1. Don’t leave batteries at elevated temperatures, such as in a car under hot sun.
2. Check the manufacturing date when you buy batteries. Don’t buy old stock. (That could be why some batteries are offered at a discount.) Don’t buy batteries for later use.
3. There is no need to prime batteries the first time you use them.

That’s all. Hope this will help you keep your batteries in optimum condition.