I found this product (check the product here) on Amazon. Can this product be able to calculate the power of my phone's battery if connected to the USB port of my phone? I want to check the original capacity apart from what the manufacturer or any file on Android says.

Will the phone's USB port output the required power for this function?

I tried 3C Battery Monitor, the app says it's 1580mAh, but its 2100mAh in websites and on the battery (it's a phone by a well-known manufacturer, but I don't want to say it here because I don't want the answers to be focussed to the phone make or the model).

  • Do note that battery capacity will wear down over time. The 3C app likely observes and reports the current full capacity, while the website gives factory (new) capacity.
    – Andy Yan
    Commented Apr 10, 2017 at 10:10
  • Is the calculated capacity be trusted? I found here (android.stackexchange.com/questions/145263/…) that the app uses two sources, one of which is the Android APIs. Android APIs can be edited if there's a root access, so it I modify it, does the app find the actual capacity? Commented Apr 10, 2017 at 10:37
  • What about the device I've provided in Amazon (amazon.in/detector-voltmeter-ammeter-capacity-voltage/dp/…)? Commented Apr 10, 2017 at 10:37
  • Tested again. This time, it is 2333mAh for the same phone. Commented Apr 11, 2017 at 6:58
  • Then I'd say that the app itself reads inaccurately. Refer to @beeshyams 's answer. P.S. Personally I have a small in-line meter (shown in this question) to measure battery capacity through fully charging, though I admit that's not for everyone.
    – Andy Yan
    Commented Apr 11, 2017 at 7:25

2 Answers 2


I am basing this answer on the concerns expressed in comments and your main question

  • Firstly, there are many ways of measuring mAH of batteries with different results, so the device manufacturer is the best person to ask this question- it claims to read battery capacity but how it measures is not known from the product description. There are different methods for hardware measurements with varying results ( a subject in itself ). See this to get a feel

How to measure capacity of a Lithium-ion battery - Electrical Engineering Stack Exchange


You could try the accubattery app, it is known to give a somewhat accurate reading. It also gives other quite interesting information about your battery.

  • It's nice to know about the app, but the device runs on Android Jelly Bean, which is not supported by AccuBattery. Commented Apr 10, 2017 at 10:30
  • I have one of those devices for my custom built race drone, I use it to check voltages so I am not sure how accurate it is on mAh. I dont think its necessary to buy such device for your use case, the apps are accurate enough. Commented Apr 10, 2017 at 10:42
  • Thanks for the review about the device. But I am concerned about the Android battery API files which might be accessed and modified if there is root permission. What if I modify the file to, like 3000mAh, do the apps provide exact value for capacity? Commented Apr 10, 2017 at 11:03
  • @Neeraj I dont quite understand what you mean by that however most of the battery calculating apps use algorithms that measure the mAh going into the phone while charging, and how long it takes to increase per percent. There isnt a single android file that tells you the true capacity of your battery after wear. Commented Apr 12, 2017 at 8:08
  • Apps are inaccurate. I've been testing for four days where I get four different readings - 1580mAh, 2333mAh, 2335mAh and 864mAh. What I mean in the previous comment was "In the question here android.stackexchange.com/questions/145263/… by beeshyams, it says about the file where battery capacity information is stored. In my findings, not only battery, but even the CPU clock speed are stored in files in /sys/. So, may be, the apps are accessing those files to get mAh?" Commented Apr 12, 2017 at 9:24

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