Battery suddenly died

Discussion in 'Motorola Droid MAXX' started by TheOldFart, Nov 6, 2013.

  1. TheOldFart

    TheOldFart Active Member

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    Actually, the battery temperature makes sense to me. I'm thinking that the battery is being heated by the electronics components heating up. Notice that the battery temperature rises when the voltage and battery percentage are dropping relatively rapidly. The electronics are heating up because the device is being used and this heat conducts to the battery. In addition, the battery is heating because it is being used. The battery heats up anytime it is charging or discharging more than it does when idle. It's the same with percentage and voltage. They drop anytime the device is being used and discharging. Screen off and little CPU usage = lower temp and lower voltage and percentage change. Screen on and more CPU usage = higher temp and greater voltage and percentage change.

    Edit: As far as the battery life on the Maxx, it is great. The original problem if the percentage rapidly falling from 50% down to near 0% was after a long usage time. This has not happened after charging back up to 100%. The 2nd rundown was smooth until a fairly quick drop from 14% to 8%. I expect that this will smooth out more now that it's had a 3rd charge.
     
    #13 TheOldFart, Nov 12, 2013
    Last edited: Nov 12, 2013
  2. FoxKat

    FoxKat Premium Member
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    Remaining battery charge percentage measurement is definitely biased towards voltage since there is no known way to easily measure how much current is still contained in a Lithium Ion battery (at least not without incredibly sophisticated laboratory equipment) - but instead only how much is being consumed at any given time based on the load and how much has been consumed over time cumulatively. Voltage on the other hand can be used as a relatively accurate indicator of charge levels by iterative solution based on two targets...the fully charged static voltage level (open circuit), and the fully discharged static voltage level (open circuit), or less accurately using closed (or loaded), circuit voltages at the same points. It's that difference which can be used, in combination with an algorithm based on the rated capacity (for a new battery), or the actual diminished capacity (for an older battery), to determine approximately where in the charged to discharged range the battery sits at any one time.

    Unfortunately that is only a rough guess since the voltage drop or difference between fully charged and what is dictated as discharged is a very small number (4.2 versus 3 for instance). Trying to measure those slight differences over many hours can result in lots of error. So the manufacturers try to use a combination of what's being consumed over time, coupled with known minimum and maximum values and using constant voltage readings to moderate or supplement these measurements. But a big part of that is knowing most accurately what "full" looks like (voltage), and what "empty" looks like (voltage again). Without a revisit of those minimum and maximum levels on an infrequent basis, things can start to stray off-course and eventually the estimated charge levels can be very far from the actual ones, resulting in the apparent sudden loss of charge you experienced. Unfortunately that's not all...battery power that is consumed faster will waste energy in the form of heat, so a battery that's used quickly will give off less cumulative total usable current from full to empty than one that is drawn on slowly.

    In your case, the phone had not seen both a full charge (powered off), and a full discharge immediately subsequent to each other in so long it lost track of what either of them looked like (voltages), and so it was guessing along the way based on cumulative consumption and dynamic voltage readings...a recipe for failure. Once the voltages reached a level that were far lower than the estimated charge levels it would expect during discharge using the old and outdated values from the last "full" and "empty" level indications, it quickly started dropping the charge level indication to "catch up", eventually leading to a full collapse and potential deep-discharge. If the battery is discharged too low (voltages much lower than 3V), the battery can actually shut down completely and become unable to take a charge at all.

    So the still bigger question is, how does one accurately measure remaining current (% of remaining charge), in a battery while it is being charged and used at varying levels of load (use)? Likewise, while charging the battery's voltages can fluctuate due to the phone consuming power at varying rates during the charge cycle and this can "fool" the charger into thinking the battery has reached full charge prematurely thereby stopping the charge at less than maximum capacity. This then results in a voltage used to indicate "full" which is lower than the true "full" voltage level, and then estimates of charge level using two variables that are wrong, and so the result will obviously be wrong as well. This is why it's recommended to do the full charge to 100% with the phone powered off every so often (2-3 months), followed by using it till it displays the "Connect your charger" indication on the screen, and then charging again to 100% with power off to set those high and low "flags" accurately for future reference in the meter's estimations. So it's very important that you re-train your battery's meter to what are the accurate full and empty levels, so it can more accurately estimate what the remaining charge is at any given time.

    As for why the meter may show lower remaining charge first (voltages) and then higher values afterwards (spikes in the graph), it is a factor of voltage suppression. If I were to measure at any one time, I may be measuring during or right after a large load period (such as playing a video that's streaming over the internet via cellular towers), and then later I may be measuring during a period where use was very low (such as while at rest). This is where the meter can indicate low levels followed by higher ones. If you read voltage during a period of high consumption due to a large load (high resistance), and then read it again once that load has been removed, the voltages will go from low to higher making it appear like the battery has suddenly and miraculously recharged itself - increased its stored energy. Of course, that's not at all what has happened. Voltage levels are impacted by current draw such that during high consumption or demand (large load), voltage levels will appear lower than during normal load or demand;

    When you are drawing little to no current you will get an artificially high voltage (known as open circuit voltage).
    When you measure voltages with a load that is an average representation of typical current consumption the voltage reported will be lower (loaded circuit or "Operating" voltage).
    When you measure voltage while current is being consumed at an abnormally high rate, the voltages will be artificially lower (load-suppressed voltage).

    When under a load, voltages naturally are "pulled down" some, the greater the load, the lower the voltage. Once the load is removed, those voltages will recover some - maybe not back to their pre-load levels but certainly above their loaded ones. To prevent those up and down spikes in the graph, some manufacturers choose to set thresholds at voltages as they're dropping, so as the voltages dip below each whole percentage or fractional voltage, the meter is prevented from displaying any higher readings later (unless actual charging has been detected), thereby preventing this artificial self-charging syndrome.
     
    #14 FoxKat, Nov 12, 2013
    Last edited: Nov 12, 2013
  3. FoxKat

    FoxKat Premium Member
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    For some reason embedded images aren't working as they used to (IT SUPPORT??)

    Anyway, you are correct, except that the battery heating up isn't due to the components heating up, it's due to increased power consumption BY the components - which is also in turn heating up the components...notice your battery "levels", the battery "temperature" and the "voltages". You can see a direct correlation between the three, where the dips in voltages are directly aligned with the spikes in temperature above, and the drops in level further above follow virtually immediately adjacent. These three corresponding indications are representing short periods or bursts of activity and battery consumption that is higher than normal. As the current draw is higher voltages drop, the resistance from consumption of higher current rates causes the battery to heat up, and with some of the current having been used this leaves less remaining charge so the levels drop accordingly. Once the loads are lifted, the voltages recover and the battery temperature begins to fall back to normal.
     
    #15 FoxKat, Nov 12, 2013
    Last edited: Nov 12, 2013
  4. TheOldFart

    TheOldFart Active Member

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    I have never seen a phone or tablet discharge lower than about 3.5v, even if discharged to 0%. Even if the battery percentage is not properly calibrated, the phone will still shut down at 3.5v, preventing a deep discharge and damaging the battery. That is why the battery percentage drops so rapidly when the voltage gets near 3.5v if the percentage is incorrect. The point of no return is about 2.8v (Battery University puts it at 2.7v), so even if a battery were to be discharged to 3.0v, it will not destroy the battery. It is common for RC buffs to discharge their batteries to 3.0v time and time again. The more conservative ones seem to stop at about 3.2v. This voltage is also common for Li-Ion flashlights. Now, I'm sure this will shorten the battery life more than stopping at 3.5v, but it will not instantly ruin the battery. Unfortunately, I was not charting or checking the voltage when the percentage rapidly dropped from 49%. However, when it instantly dropped from 14% to 8% the second cycle, the voltage was still about 3.6v. I've since deleted the widget in use at the time, so I don't have the graph to post.

    I would imagine that the components heating up also contribute to the increased battery temperature, even though the battery discharging is the major factor. That's why I posted "In addition, the battery is heating because it is being used." I was going to change the post to make that the primary point, but I was too lazy to change it. I will be discharging both the Maxx and my One until they shut down this cycle to make sure that they shut down at no lower than about 3.5v. I'll monitor the voltage the last few percent. My One was at 3.605v when I shut it off at 10% yesterday. Running the phones down to 0% should not be any problem, as 3.5v is well above the voltage that will shorten the life.
     
    #16 TheOldFart, Nov 12, 2013
    Last edited: Nov 12, 2013
  5. mountainbikermark

    mountainbikermark Super Moderator
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    What I'm talking about is where everything is raising at once. Is this indicating it's being charged ? That's where I'm baffled. The rest of it makes sense, spikes in usage will correspond with both drop in numbers but rising temps as y'all have said .
    Have you tried Watch Dog Lite and a real time cpu ?

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  6. TheOldFart

    TheOldFart Active Member

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    Yes, the phone was being charged where the graph color is green. As you can see, it stayed plugged in for some time even after it reached full charge.
     
  7. FoxKat

    FoxKat Premium Member
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    You are right on all points. The phones are spec'd to battery levels much higher than 3 Volts when they're supposedly discharged as you indicated, that's why I said "much below 3 Volts" when talking about the protection mode. Under normal conditions with a meter that's calibrated properly discharging to 0% shouldn't be an issue. Only concern is that I've worked with many phone owners whose phones have dropped dangerously close to protection mode in situations like yours and have become unresponsive to charging (white light of death).



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