Measure battery capacity in iOS, iPhone

I wrote on January 7, 2018 that I get inconsistent results using the app Battery Life.

Today it was recommended to me that I download the app

coconut battery

onto my iMac and use that to measure battery capacity on my iPhone. So far I am getting more consistent results but it takes some tries to see if they make sense. So far my iPhone battery is reading 73.3% currently. Earlier readings were 73.5% and then 73.4%.

Note, this is not an IOS app. It is a Mac OS app so one downloads it to the Mac and then connects a cable to the iPhone to be measured.

John,

Thank goodness I haven't completely lost my electrical engineering education. But I worked on digital and analog radios in the telecommunications area and someone else was doing the power supplies and still others were specifying the lead-acid batteries. Think two banks 24 each 2 volt batteries of enormous size. And a diesel motor generator in case electrical power to the site was lost. One could fit 500 or 1000 iPhones into the space required by those battery banks.

Amperes are coulombs per second. It would be possible to meter the milliAmperes and the battery terminal voltage and determine how many coulombs were required to bring the battery up to the specified voltage. But I'm guessing that the fully charged voltage will also be affected by battery chemistry. I've never mucked with lithium ion batteries but I do a lot of recharging of AA and AAA rechargeable batteries which are a different chemistry. The maximum voltage that those batteries can reach decreases after they have been recharged many times.

But, as you rightly point out, it is very difficult to know how thoroughly the iPhone is sleeping when it is turned off unless it is completely powered down and then recharged. And then completely powered down I can't read the % of charge. When I was working I had access to nifty milliAmp meters and I still have my Fluke Volt Ohm meter but there are no test points available.

I just downloaded and installed Battery Life per Brian's suggestion below. The state of charge built into the iPhone says 86% and Battery Life says 80% Good. I'll have to figure out on my own if the two numbers were intended to match up.

John,

Thank you for the information and confirmation of my basic understanding. With 2 years of heavy usage on my iPhone, I'll wait until Apple starts offering the replacement batteries at $29. I can't believe that I won't see an improvement in how long I can run my iPhone before it needs recharging with a new battery.

I followed Brian's suggested and downloaded and installed Battery Life.

Over the course of several days using this app, I've seen battery capacity rated at 50, 73, 80, 86 and a few others in that range. I really don't see how one can take Battery Life to get an accurate measure of battery capacity. Maybe some of its other features make it worthwhile but I don't think anyone should think that they will get a repeatable, accurate rating of battery capacity.

50% is a very low capacity, replace your battery right away before you iPhone leaves you stranded.

86% is not bad, your battery is going bad but there is no rush to replace it,

80% is marginal, get your battery replaced pretty soon before it starts causing you problems.

I've gotten all these readings and not in that order. One would expect battery capacity (as distinct from percentage charged) to be a gradually or perhaps rapidly decreasing number. If the measurements displayed by Battery Life were accurate, the readings should be uniformly decreasing. My most recent reading of battery capacity was 80%.

The Romans would have said "*** granis salis". Make that a large grain of salt. Maybe a whole salt lick.

Well, I followed your links and changed a number of things in Settings, turning off notifications for lots of apps and turning off Location Services for a few.

Pardon my questioning your statement "That's really not a very useful measurement." I think of battery capacity in terms of mAh. I presume that the battery is specified to supply a certain number of milliAmpere hours of current while the output voltage stays at or above a specified voltage. As the chemistry in the battery ages, the number of mAh that can be supplied is reduced. Turn that around. I think that the charger is built to supply a certain number of milliAmperes of current up to a certain voltage and then it probably is engineered to supply a smaller current while the voltage is rising further in order to prevent overcharging. There might even be a reduction to just a trickle current to keep the battery fully charged but to further reduce overcharging and overheating. I'm guessing this. I obviously did not design the charger. But I have a fairly complete layman's idea of how batteries operate. So If the capacity of the battery has been reduced, then the battery should recharge from very low voltage to fully charged voltage quicker than if the battery has its original capacity. I've observed that the battery indicator rises at a rapid rate up to 80% charge and then it takes much longer or is charging at a lower rate to get from 80% to 100%. That observation reinforces my guess about how the charger is designed to charge the battery. And maybe the are actually power control circuits within the iPhone which are actually changing the charging rate. The effect is the same whether the charging rate is controlled in the charger or circuits within the iPhone.

So if I am correct that the charging rate is a fixed amount of current into the battery, then the lower the capacity of the battery, the faster the battery should charge from empty to at least 80%. And therefore and I'm still guessing, the rate at which the battery indicator increases from 1% up to 80% might give a good indication of battery capacity. Thanks for your thoughts and knowledge.

As an aside, my above reply was edited by the gods. The word in Latin for "with" was translated to three asterisks because the same word in English has an unwanted sexual meaning. I wonder if Google can translate "with a grain of salt" to Latin without editing itself.

You got that right!