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Need app that correctly displays input amp/volts

Discussion in 'Android Apps & Games' started by Bodycount, Mar 5, 2016.

  1. Bodycount

    Bodycount Android Enthusiast
    Thread Starter

    I downloaded the app "Ampere" thinking it would tell me how much amps and volts my phone is receiving. I don't think it's correct.

    I own a Samsung S7 egde. Has the quick charge 3.0 spec to go from empty to full in about an hour. Here are some tests I used with various chargers:

    0.7 amp standard wall charger: Showing as 400-500 ma on screen

    Samsung wireless charge pad (standard one): Showing 300 ma on screen

    Samsung wall charger that came with my Note 3 rated at 2.0 amp: Showing 1000 ma on screen

    Samsung wall charger that came with my S7 Edge and is quick charge 3.0 rated: Showing 1000 ma on screen.

    For the Samsung wall charger tests I used the cables that came with the unit.

    I would think the 2.0 amp wall charger would show more than 1000 ma. And most definately the new Samsung wall charger that came with my S7 Edge that is quick charge 3.0 certified should show a lot more than 1000 ma.

    Is there an updated app that might be better?

  2. electricpete

    electricpete Android Expert

    I think it's just looking at rate of change of battery level. If we ASSUME (*) no usage during the test, we can compute milliamps knowing rate of change and design battery capacity.

    Of course that's a bad assumption, especially with screen on. The more juice your phone is using during charge, the farther the calculated charging current below actual charging current
    psionandy likes this.
  3. Bodycount

    Bodycount Android Enthusiast
    Thread Starter

  4. Bodycount

    Bodycount Android Enthusiast
    Thread Starter

  5. RazzMaTazz

    RazzMaTazz Android Expert

    I don't know, but (as an electrical engineer who has worked in the consumer electronics industry for many years) it seems unlikely that phones would directly measure amps running into the phone or running into the battery, and therefore it seems unlikely that an app could report such data. It's certainly possible for phone makers to embed such circuitry but it seems like an unnecessary expense. I imagine the app is making some estimates.

    Even if the app is accurate, the Quick Charge 3.0 spec allows the phone to request different voltages based on its needs. Therefore, I'd assume, that charging power-consumption varies depending on whether the battery is nearly empty or nearly full. Watts = Volt x Amps.

    Unless the cable has a flaky connection or is get smoking hot, I'd be a bit surprised if the USB cable would make any difference in charging times.

    It seems to me that the only thing that really matters is how long does it take to charge the phone with each of the different chargers. I can understand the desire to be able to quickly "see" the rate with an app, rather than running through a full charging cycle with each charger. But I think in this situation, the actual experimental results are far more valuable than a million "expert" opinions or app/charger measurements.
    El Presidente likes this.
  6. electricpete

    electricpete Android Expert

    I agree wholeheartedly. And we certainly can offer that advice for any question related to battery charging / discharge rates (best info is test on your specific setup). It is undisputably true. At the same time, I don't view it as a negative that people like myself and other responders have offered an opinion based on our own knowledge and our own experience that will still be of use to op if they decide not to do an experiment. And for that matter, even if they choose to do they own experiment, scientific method requires both hypothesis and experiment... it's tough to design useful experiments without hypothesis to capture what may be the relevant variables.

    That part about "expert" opinion really got my attention. Usually with quote in this fashion it's intended to emphasize the non-expert nature of opinion offered by someone who claims to be an expert. (it would be completely different if both words were quoted: "expert opinion"). But there are no links to articles in this thread. To whom is it directed... all previous posters? I'm just asking,.... I hope I'm misunderstanding and you can explain what you meant.

    You and I agree on the part that most phones these days don't have charging sensor. I've used Battery Monitor Widget for a long time. The dev (3c) has got a website with a forum that has a lot of details hidden among hundreds of posts in his forum, but they're not easy to find and I haven't been looking there in years. One thing he makes clear is that some devices have a battery charging current sensor and others don't. He has a list of these devices somewhere but I can't find it... none of my phones have ever had it and my impression is it's rare. What is obvious from the graphs provided to me by the BMW app is that the current and %/hr reported by the app are associated with the net battery increase rate (charging minus usage). This is based on the following:
    • The plotted milliamp curve changes from single negative curve during duscharge to a single positive graph during charging (with no breakdown) so it seems very logical that the curve must include both charging and usage effects during charging (it's net).
    • I have observed the indicated "charging current" gets lower as you use more juice during charging.
    • The dev's definition of reported milliamps is basically change in battery stored energy vs time. That is a net charging rate.
    The data recorded by the app are battery level, battery voltage and battery temperature. So it uses these data to make an estimate. The battery level is most directly relevant (for net change rate) but is only updated in 1% increments. So the battery voltage and temperature are input to a funky model that helps fills in the gaps in between.

    Certainly other apps may work differently. GSAM monitors a variety of other parameters which helps it attribute your battery usage to various categories and apps. But even gsam doesn't provide anything other than a "net" %/hr during charging. If gsam goes to all that trouble of characterizing usage but still doesn't split out the components of net during charging, I doubt other apps (that don't even report usage statistics) would be able to do it.

    This thread showed that cables can make a pretty big difference. There are a lot of variables that CAN affect charging rate and cable is one (but whether cable is important also depends on charger and phone). And I'm willing to bet that the 36" cable at the link which caused the lowest charge rate ran no hotter than the 12" cable with the highest charge rate (same wire gage). I think you'd agree "smoking hot" is not a very reliable indicator to look at for indication of total cable resistance, unless we had already considered the cable length (which was not previously discussed).

    These are just my thoughts. I am not claiming to be an expert.
    #6 electricpete, Mar 7, 2016
    Last edited: Mar 7, 2016
  7. svim

    svim Extreme Android User

    I'd say you're doing OK with the Ampere app already. You're collecting a good amount of benchmark data to figure out how to optimize your battery charging already. By mixing info from Ampere with another app that might be using a different matrix your data won't be valid. Battery charging numbers are not going to be a constant, the numbers you see will always be variable. Your S7 Edge has a 3600 mAh battery, or 3.6 amps. With any typical 5 volt, 2 amp rated charger you're rarely going to see even the full 2 amps being fed into your battery -- you'll see more amperage early in the charging process and it will taper off as time goes on. But it's never going to be a issue where there's a constant 2 amps of current. You might possibly get some slightly higher numbers by using a heavier gauge, high quality USB cable but it's not like you can expect to see anything like 3.6 amps even if you're plugged into a power supply with that kind of output.
    (Oh and if you are messing around in that 3+ amp range, you're battery is probably pretty hot so you'll not only want to be measuring current numbers but temperature numbers.)
    #7 svim, Mar 7, 2016
    Last edited: Mar 8, 2016
  8. Bodycount

    Bodycount Android Enthusiast
    Thread Starter

  9. RazzMaTazz

    RazzMaTazz Android Expert

    Electricpete: My reuse of the old, old saying, "One experiment beats a thousand expert opinions" was not directed at your reply, nor intended to belittle anyone's opinion nor discourage other replies. Holy smokes! When in doubt, please save us all some time and give others the benefit of the doubt.

    Apparently I was wrong about USB cables making a difference. Longer cables and cheaper (especially higher 28/24AWG) cables apparently can have significant resistance and therefore can cause longer charge times on modern (higher power) phones, so many micro-USB cables are now 20AWG. I'm really surprised. I probably won't be buying anything less than 20AWG from now on. Not much sense in buying a high-power charger if the cable is going to defeat it.

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