This experiment is kind of old as it dates back to 2012, a lot of changes happened since then, big and small. However we will still learn something from it since it relates some basics about lion ion battery, which seldom changes tremendously these years.
This post will cover two aspects: how to take advantage of the quick charge feature on your handset, and do you need to plug out immediately your phones indicates charge completed.
The test started with an Android phone U8800 by Huawei, an original charger at 1A, and an iPad charger at 2A and a power meter. As you might know the quick charge tech introduced by Qualcomm charges a battery much faster. So people generally will think a 2A charger reduces the charging time. And it does in most cases but that’s not always the case.
I started charging the phone once the battery went down below 30%. At the same time, wrote down the time, battery level and input power. The first charging was done using the iPad charger, second with original charger. The charge typically ended when the power meter reading stopped changing.
The test first began with iPad charger. As can be seen from below diagram, it took nearly 5 hours to charge a 1500 mAH battery from 35% to 100%.
When the phone showed the battery level at 24%, it took about 5 minutes to reach 31% and the input power is 3.04W. The whole charging progress slowed after the battery level went up to 40%. For instance, it cost 29 minutes from 80% to 87% and input power remained at 2.93W. Eventually the input power went down gradually until it reached 1.63W, and it stayed at that forever. This is only naturally as the voltage increases and the battery got full slowly. However it does remind us that the battery is not really full even the phone showed 100% battery level.
The same holds true with the original charger. It took over 5 hours too, see below diagram. It seemed to me the iPad charger does not work as expected. This might be that the phone only accept no more than 1A current to protect itself. So if you have a quick power charger, you also need a phone supports quick charge to make it work.
I next went to test if I can get more current into the battery after Android says it’s full. The test was easy, plug out immediately when the phone shows 100% battery level. Then kill all processes and services, watch an online movie until the battery goes dead, and record the time. Now charge it again until the power meter readings do not change, and play the same online movie again and again until the battery dies. And here is the result, a 12% difference. Check out the chart below. It did prove that you should continue to charge your phone even it says battery 100% full, but no more than an hour and a half. Any time longer than that is in vain.
The whole test took over 30 hours and here are what I learned.
1. The battery level by your phone is not accurate; this is especially true during 5% and 25%. A 1% drop does not mean anything, but a 15% drop does.
2. You need both a quick power charger and a quick charge enabled phone to speed up the charging process.
3. You need to charge your phone one more hour even your phone says battery full.
Quick charge 1.0 was first announced by Qualcomm back in 2012 which claimed to charge your phone up to 40% faster than older chargers. Quick charger 2.0, however makes the charger 75% faster than the old chargers, and about 25% faster than quick charger 1.0. Qualcomm claims that the new tech will charge a 3300 mAH battery to its 60% capacity in 30 minutes.