Are battery monitors accurate ?

Question

I use GSAM battery monitor. i have flashed a few roms,

I get this reading:

~91% battery. 460ma current consumption with regular use(full brightness). 3:40 hours time left(avg last 5 minutes).

So this means that my 91% battery should hold around 1800mah-2000mah (460*3:40) , but this is strange because my battery is a 4100mah battery, and i have it only for 8 months.

Another strange thing: when i look at Android's battery statistics, the sum of percenatges of the battery that goes towards each app(including screen) is only at ~50%.

As a fix, i tried to recharge my phone to 0% and than fully charge. but the problem stays the same.

So what does this mean ? and are my battery problems due to software or hardware?

Answer 1

Are battery monitors accurate ?

Battery monitors are an approximation and not accurate :

• They are usually based on Voltage measurements

• You need Voltage and Current measurements to get an accurate picture. Most phones have only Voltage sensors. Current sensors ( Coulomb Sensor) are available in some at OEM discretion ( Honor 6 for example). Even if the device has it, the kernel ( since you mentioned flashing ROMs) need to support it. For more details, see this How does the Android estimate the battery level without a current sensor?

I don't know about your device but let's assume that it has only Voltage sensor as is common. Problems with accuracy using voltage sensing ( apart from current sensor bit)

• How often it needs to be updated (and reflect on the status bar), AFAIK is left to OEM implementation. Is the battery icon on your Android phone telling you the truth? says that updating battery SoC information is manufacturer dependent and not Android driven (emphasis mine and I haven't found any other source to dispute this)

  We contacted Google about this, and the indication is that the battery data given in the Settings is the correct one. The updating of the icon happens "every so often", we're told; quite how often is entirely up to the manufacturer, rather than being part of the Android code

• Further voltage is NOT a true indicator of the amount of charge. This will explain in detail why

• Yet another problem with Voltage based measurement is battery behaviour. Li Ion batteries display a "flattish" voltage drop even though the amount of charge falls relatively steep as seen here at Fig.2

Your app like other apps uses Voltage and inherently plagued with inaccuracies, so at best gives a rough estimate

• Starting from Lollipop Android gives you an estimate of how long your battery is going to last, so the interpretation in other answer is valid

• Another strange thing: when i look at Android's battery statistics, the sum of percenatges of the battery that goes towards each app(including screen) is only at ~50%.

Measurement of consumption per app and therefore total can also be misleading. This post, though old sheds light on this How does Android calculate battery consumption by apps?

Now coming to your concern of battery problems - it's hard to say. I would suggest that you revert to stock ROM and then observe to establish ,if, there is a problem ( Could be custom ROM, kernel too)

Answer 2

Most popular battery apps including GSam, Ampere, Power Tutor, and Better Battery Stats do not report accurate current readings. OEMs and SoC manufacturers must be able to measure power consumption using hardware and software-based methods. Every mobile device has one or more power management ICs (PMIC) and battery fuel gauge software. If a developer understands how to access this data and interpret it, they can get accurate voltage and current readings, which can be used to calculate accurate power consumption. I know this because I’ve tested software like Trepn Profiler and Battery Mentor using a $700 Monsoon Power measurement hardware and found them to be within a few percentage points off in most use cases. It’s important to mention that newer chipsets and operating systems have made power measurement much harder and in some cases even these apps are now having problems. Some OEMs (e.g. Samsung) also prevent access to this data. [Disclosure: I work on the team who created Trepn and have given advice to the person who created Battery Mentor.]

Answer 3

Specific to your case

First of all I think your assumption is wrong. When the app states:

~91% battery. 460ma current consumption with regular use(full brightness). 3:40 hours time left(avg last 5 minutes).

This rather means you have 91% capacity left, or in your case 3731mAh from 4100mAh. It's currently drawing 460mA with regular use having screen on full brightness. And based on the average of the last 5 minutes you have 3:40 hours left.

So the 3:40 hours is not linked to the 460mA the way I read this information.

I didn't go through it but this user guide from the authors might give you more insight.

In general

I have no experience with that app but first of all you'd want to know how that app calculates these numbers. The app doesn't look like open source so reverse engineering it or contacting them seems like valid options.

The time left on these apps are always an indication based on what you did up to that time (and often starting from the time you stopped charging the phone). Nothing more than a prediction. If you use the phone more/less for the next hours it won't match reality for sure.

This app has some ratings in the store indicating there are bugs:

Martijn Kösters 5 januari 2017 Starting app Has to be done manually after fully charging. Otherwise fine. Strange?

robert zegers 21 oktober 2016 Bug The widget keeps getting stuck on a certain percentage.. I have to reboot my phone to fix it. Ive got a Oneplus 3

See play store link for more.

If this intrigues you you could always do tests and see how accurate these numbers are. How long does it last you in real life? Are you having issues with battery life? If so try to find out what app causes it by using the Android battery statistics.