Here is a great little laptop battery utility I have been testing. I found it so essential, that it's now on all my laptops.
Windows offers an icon that can show you the percentage of charge left in your laptop battery. I feel like it will also give an estimate of the time remaining on your battery, but in preparing this article I couldn't get that information to display.
In any event, BatteryBar Pro displays in your taskbar at the bottom of your screen, and provides far more information than does the Windows battery icon.
To start, it shows the remaining charge in your laptop battery, and if your computer is plugged in, shows the time remaining until it reaches a full charge. I would have never thought I needed this latter feature, but when I'm headed out to a few hours of writing at an ocean side coffee shop (for some reason the roar of the ocean and the hubbub of the coffee shop is the perfect backdrop for writing), it's nice to see how much longer I have until the battery is fully charged. BatterBar gives the specific time the battery will be fully charged. If only a few minutes are left, I may have a cup of coffee and wait for a full charge. (I often have a coffee before heading out for coffee. It's a sickness, I know.) That's far better that seeing only that the battery is 97% charged, with no indication how long the remaining 3% will take.
An awareness of battery life is a good thing. I don't like worrying about the availability of an AC outlet. At one particular Barnes & Noble I frequent, getting a seat near an AC outlet in the café is about as likely as spotting a Yeti in the romance aisle (they prefer to hang out near the magazines). I have an ultrabook that will get me through an entire depo without charging, but I also have a beautiful 17-inch HP laptop that I prefer to use for writing, but it's charge only lasts about 3.5 hours. The intended task and the battery life dictates which one I take.
Based on my experience, BatteryBar offers a much more accurate reading than the Windows utility. It maintains historical information on how long it takes your battery to charge and discharge, which apparently enables it to be far more accurate.
BatteryBar also displays the capacity of your battery in milliwatt-hours (mWh). This can be useful if you have multiple batteries with no obvious indication of their relative sizes.
But the final feature is what I find really killer. It is able to determine what it calls the “battery wear” of your battery. You have probably experienced the reality that your laptop just doesn't go as long as it used to. That's because rechargeable batteries only last so long, and soon they can no longer hold a full charge (or at least don't hold a charge as long). BatteryBar shows how much of your battery's storage power has been lost. For example, in the picture, you can see that the battery has a stated size of 86,580 mWh, but 31.7% of that has been lost. This information let's you know it might be time to get a new battery (or to start taking two).
BatteryBar Pro offers a free version that is really all you need, but if you are a power user (get it?), there is an upgraded version that contains additional features, including customizable icons, low battery warnings and easy access to the Windows power schemes. This upgrade supposedly costs $8 for a lifetime license, but there appears to be a perpetual 50% off offer. Go here (not an affiliate link) to download BatteryBar Pro for free, to see if you like it as much as I do.