[Galaxy Note GT-N7000 General] g3k:
Yes it's accurate if you respect the conditions

Hello,

Being a long time user of Battery Widget Monitor, i wanted to try that Nova tester, though at first sight, i've thought it would be another useless "battery info collector" to show nothing more than Android but in a fashion way.

No. In fact, this tool can succeed to reveal reliable results. I can confirm that. But the user should pay attention to assure stable testing conditions.

If you assure the following, the final mAh value should be close to reality:

1) Keep brightness at maximum during the test. Don't try to tweak it after the test starts.

2) Same for all wireless connections. Phone, wireless, bluetooth etc. They must be all disabled. You tweak it, you get lower mAh result.

3) In case you overclock your CPU, don't do it during battery test. Set it to default stock speed, default governor. If you leave it overclocked and on performance governor for instance, you will see a lower mAh result.

4) Forget the standard and fast tests and prefer the full test from 100% charge. Larger drain cycle is better for reflecting the whole capacity. Faster tests can also calculate results but these would be just a sample area of the whole battery cycle.

5) Don't mess with the device until the end of the test. Let it drain peacefully :)

The main advantage of this app is measuring the capacity through a drain cycle which is a better simulation of "capacity". Battery Monitor Widget is not too bad in measuring mAh value either but it uses the charging cycle.

However, do not forget that all batteries are rated according to constant 0.1 C discharge rate by their manifacturers, like 250mA for a 2500mAh battery. Thus, a standard capacity mesaurement requires a test of 10 hours exactly, which is too long to spend for end users without using the device.

Hopefully, Nova goes faster than that, like 2-3-4 hours for a full test, at 0.3-0.4C discarge rates. Although the duration looks bearable, the pay-off is probably a result below the battery spec. The more is the discharge rate, the less is the capacity measured as a basic rule!

Even a brand new battery may give lower mAh than what's written on it's label. Don't be surprised and remember that 5% to 15% less is just usual even for a new battery.

The app certainly needs to use a current value as a key parameter, either via internal sensor (better case) or from the developer's database (when no real time value). The calculation method is not hard to decrypt at all. It tries to measure the average of the time needed to lose 1% of the charge during the whole test and multiplies this by 100 to estimate total battery time. This total expected time of a full discharge from 100% to 0% is then multiplied by the average current value to obtain hours x milli amps which is exactly the mAh value we need to know.

That's why the mA value is certainly necessary and without it, no mAh value will come but only a test time. If your device can't report the mA by itself and if the device is not found in the database either, you can just uninstall Nove tester.

My 1 year old N7100 Galaxy Note II has a 3100mAh. It was measured at 2600 mAh during full test. The mA was not reported by the OS, alhough i know it exists somewhere in the OS becaue BMW can see it. Nova could not. No worries anyway, the database value of 859 mA was used to calculate a result. By using above formulation i was able to calculate the same mAh. If the result is not accurate here, the only thing to blame would be that 859 mA value. If the database average value is correct, the result is accurate.

That why you should respect the test conditions, especially if you have to use a database value. They come from identical devices with max brightness, flight mode, stock cpu etc.

Try and see for yourself.

PS: I mention mAh value as capacity unit above. However it's not the correct unit by definition but people understands this better than Wh which is the correct capacity unit. Please know that a 3100mAh battery is always a 3100mAh battery until death. Read it like speed. What matters is the distance, speed by time, which is Watt.hours for batteries. They lose WH and not mAh, in fact.