There are many factors which affect the accuracy of battery level readings. Two of these include the manufacturer of the phone and the type of battery used. Both Battery Notifier BT Free, and Battery Notifier Pro BT display battery levels provided by the system, so often we have to investigate why the phone or tablet you own may be giving you an inaccurate reading if you are using the battery that came with your phone.
What complicates matters even more is if you use extend batteries. If you switch batteries a lot, or use different batteries of different sizes, getting an accurate battery level reading from your phone can be a tricky proposition. This is because there is a file inside your phone which attempts to give you accurate readings over time based on what it thinks is the standard battery for your phone from the manufacturer. If you root your phone, you can wipe this batterystats.bin file and start over if you start using a new or extended battery to get more accurate battery level readings. However, most users do not have this option. Therefore, I did some research to try and find out from manufacturers what they suggest in order to get accurate battery level readings from extended batteries.
SAMSUNG EXTENDED BATTERIES
I was unable to get the necessary information from Samsung support at their website or by using their live chat support, but I did find someone at Amazon.Com who had bought a Samsung extended battery, who left a review saying what the instructions he received from Samsung said to do to get accurate battery level readings. They said to completely discharge the battery, then to fully charge the battery with the phone off. They instruct you to then repeat this procedure at least three more times back-to-back.
MOTOROLA EXTENDED BATTERIES
While you apparently can use Motorola extended batteries that were meant for other Motorola phones or tablets in your device, according to Motorola it may not work correctly with the battery level meter software in your device. It may "show no battery strength left, when in fact, the battery will still last for a very long time". Therefore, be extra careful and make sure you have the correct extended battery for your specific Motorola phone or tablet. I also would follow the advice that Samsung gives for Motorola batteries as well.
HTC EXTENDED BATTERIES
I was unable to find any specific relevant information in regards to getting accurate battery level readings on HTC extended batteries. Again, I would just follow Samsung's advice.
THIRD PARTY EXTENDED BATTERIES (Not recommended)
1) Before you charge the battery for the first time, be sure and drain it completely until your phone or tablet turns off.
2) When using an extended battery from a third party, you may need to fully charge the extended battery after each drain. The reason is because the battery may exceed the amount that your device's firmware can handle, and your device may not recognize the third party battery you are using, even though the company you purchased it from says it will work in your device. You also will need to keep charging the battery for an additional 2-3 hours or more AFTER your phone or tablet reaches 100% or says it is fully charged. How much more may depend on the difference in ratings between the manufacturer's standard battery, and the third party extended battery you are using. So, for example, if the standard battery in your Samsung Galaxy Nexus is rated at 1850mAh and takes about 2-3 hours to fully charge, the third party Seidio extended battery rated at 3800mAh might take 6 hours or more to fully charge. I would just charge it for 8 hours the first time. Just be sure you drain it completely first.
3) This next step requires you to check with the instructions you received with your third party battery. If you lost them or did not receive any instructions, you will need to contact the manufacturer of your battery to ask them the procedure you need to take next to get accurate battery level readings. One manufacturer simply suggests you reboot once your device is reading between 40-50% and then "subsequent rebooting will give you consistent and accurate readings." Another has the following instructions at their website...
Troubleshooting (Inaccurate Extended Battery Readings):
Step 1: Charge battery for 8 hours prior to first use, then use battery until it dies
Step 2: Once your phone is 100% dead and has shut down, leave it shut off. Proceed to charge it until it reaches 100%; then leave it on the charger for an extra 3 hours.
Step 3: Turn on phone and use it until it dies. Repeat Step 2 five more times, and on the fifth cycle leave it on the charger for an extra 4 hours.
They then suggest if the battery still is not giving accurate readings, to download an app which measures battery voltage (which fluctuates), and in the app description it says:
NOTE: To get the most accurate readings, calibration can take several days.
So even if you follow all the above instructions, it seems it may take you up to two weeks to get "the most accurate battery reading" with an extended third party battery. For this reason, and because there are so many reports of third party batteries not performing up to specs, we recommend against using third party extended batteries.
SWITCHING FROM A STANDARD BATTERY TO AN EXTENDED BATTERY
If you are switching back and forth between standard batteries and extended batteries, you will have a difficult time getting an accurate battery level reading. To repeat, there is a file called batterystats.bin in your device that stores information on your past battery use in order to give you more accurate level readings going forward. You can delete or reset this file if you root your phone, but we do not recommend that you root your phone as this voids your warranty and leaves you more vulnerable to hackers. We again suggest you do what Samsung recommends, which is to completely discharge the extended battery, then fully charge the battery with the phone off, and to do this at least three more times back-to-back.
(NOTE: Fully draining your battery on a regular basis is not a good idea. To prolong the life of your Lithium Ion battery, it's best not to even let your battery level drop below about 25% before recharging. Partial charges are always much better for your battery than fully draining it to zero repeatedly. However, the steps suggested above may be necessary if your extended battery level reading is not accurate.)
If your extended battery levels are still not accurate after following Samsung's instructions a total of 5 times, you may need to wipe the batterystats.bin file. You can still wipe the batterystats.bin file without having to root your phone by doing a complete system reset. Although some may consider this to be a rather drastic step, it is better than having your phone turn off when it is still reading 40%. If you take precautions to simply backup your contacts and important information you don't want to lose, this step need not be that painful. Any apps you have downloaded will be gone, but Google Play will be able to restore the paid ones, and often some of the free ones. Google will be able to restore your contacts and calendar events as long as you sync them with Gmail first. Your network settings will be restored as well as your bookmarks.
If you do decide to do a system reset in order to wipe the batterystats.bin file, I highly recommend that you backup all your contacts and as many apps as you can anyway. (You can never be too careful.) Because I like to do this myself, I use the paid version of SystemPanel ($2.99) which has a really nice and easy to use archive feature which allows you to backup most of your apps to your SD card one at a time. The paid apps that don't allow you to do backups, can always be downloaded again from Google Play if they aren't restored after the system reset. Simply make a list of them, and use the same Google e-mail address that you signed up with, and you will be able to download the apps you paid for without having to pay for them a second time.
Getting an accurate battery level reading when using extended batteries seems to be a fairly well known problem on the Internet. Hopefully the information in this post can help. And a reminder for Motorola users with 10% increments, the 1% Motorola fix we provide is a workaround that is meant to work on STANDARD batteries from Motorola.
