In this part, I want to answer some of the questions that were asked in the first article. Below is information about various improvements to wireless charging and a little information about the power received depending on the location of the phone on charge.
Modifications
There are various "chips" for wireless charging:
1. Reverse charging. There were a lot of comments about her, there are also comparisons and reviews on the Internet. What are we talking about? The Samsung S10 and Mate 20 Pro have reverse wireless charging. That is, the phone can take charge and give it to other devices. I have not yet been able to measure the strength of the output current (but if you have such a device and are interested in testing, write in the messages :), but it is indirectly equal to 3-5W.
It is practically not suitable for charging another phone. Suitable for emergency situations. But on the other hand, it is great for recharging gadgets with a smaller battery: wireless headphones, watches or electric toothbrushes. Apple is rumored to be adding this feature to new phones. It will be possible to charge updated AirPods and maybe a new watch.
For information, the battery capacity of wireless headphones with a case is approximately 200-300 mAh, this will affect the phone's battery more, by about 300-500 mAh.
2. Charging power bank by wireless charging. The function is similar to reverse charging, but only for Power Bank. Some models of wireless power banks can be charged with wireless charging. The received power is about 5W. Given the usual common batteries, such a charge will take about 5-15 hours from wireless charging, which makes it practically useless. But as an additional function, it also has a place to be.
And now to the main thing:
How does the received power change depending on the location on the charge?
For testing, 3 different wireless chargers were taken: X, Y, Z.
X, Y - wireless chargers for 5/10W from different manufacturers.
Z is a wireless Power Bank with 5W output.
Prerequisites: The same Quick Charger 3.0 charger and USB to Micro USB cable were used. I also used identical beer coasters as plates (from a personal collection) that were placed under the meter. The meter itself also has a protective plate 1mm from the coil, which I also added to all values. The thickness of the top cover above the coil was not taken into account. To measure the range of the received charge, I recorded the maximum values ββthat the meter caught. To measure the charging zone, I wrote down what the meter shows at a given point (I took measurements first along and then across. Since the coil is round in all charges, the values ββ\uXNUMXb\uXNUMXbare almost the same).
Charges in the test had one coil.
First, I measured the received power depending on the height (thickness of the phone case).
The result is the following graph for charging power at 5W:
Usually, in the description of wireless chargers, they write about the width of the case up to 6 mm, this is approximately what happens for all the charges of the test. Further 6mm charging either already turns off (which seems more correct to me) or gives very little power.
Then he began to test the power of 10W for charging X, Y. Charging Y did not hold this mode for more than a second. It immediately restarted (perhaps it works more stably with phones). And charging X gave out stable power up to a height of 5mm.
After that, I began to measure how the received power changes depending on the position of the phone on charging. To do this, I printed lined checkered paper and measured the data for every 2,5 mm.
Here are the results for charging:
The conclusion from them is logical - the phone must be placed in the center of the charger. A change of plus or minus 1 cm from the charging center is possible, which will not have a very critical effect on charging. This works for all devices.
Next, I wanted to make some advice on how to get to the center of the charging zone. But this is too individual and depends on the width of the phone and the model of wireless charging. Therefore, the only advice is to place the phone in the charging center by eye, this is enough for a normal charging speed.
I must make an important caveat that this may not work for some charges! I came across chargers that could charge the phone only when hit 1v1. With vibration from 2-3 sms, the phone has already moved from the charging zone and stopped charging. Therefore, the graphs above are just a rough measurement of three charges.
The following articles will be written about the heating of chargers, chargers with multiple coils and new developments. If someone from the owners of Samsung S10 and Mate 20 Pro also has a thermometer or multimeter with temperature measurement, then write :)
For those who want to help with measurementsOr if you are an expert who will help me with writing articles, then you are also welcome. I wrote in the first article that I have my own charger store. I relate to charging mainly from the side of user characteristics, I measure and compare everything in order to offer buyers what works. But I'm not completely savvy in technical details: boards, transistors, coil characteristics, and so on. Therefore, if you can help in writing articles, developing new products, improving, then write!
Source: habr.com