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March 15, 2013

Wireless Charging

Who needs it right? I mean, we need wireless charging about as badly as we need "remote keyless entry". So there you are, walking up to your car with the key fob in your hand, so obviously if the key is already in your hand, you don't need keyless entry. That's about how useless wireless charging is. We don't need it, it's just cool to have.

Now before we get started, you must realize that wireless charging requires that your device be equipped to charge wirelessly. This usually means that it has a built in coil or has an aftermarket coil installed. You cannot just take any old device and put it on a wireless charger and expect it to charge. And (with some exceptions) you cannot charge a device with a receiver using a different charge standard.

A quick (and obviously very general) explanation would be. . . a charger (transmitter) has a coil which uses electricity to create a magnetic field and a logic circuit to sense the presence of a receiver so as not to create the field when it's not needed. The receiver has a coil which converts that magnetic field back to electricity. When you place the receiver in the proper proximity to the transmitter, it creates the magnetic field and monitors it for feedback and the receiver charges the device. Wireless chargers for phones normally charge at about the same rate as a USB connection, but not as fast as a normal wired transformer connection.

At night you place your phone haphazardly on a charging pad and in the morning you pick it up and go. Then whenever you get in the car, you put your phone in the car cradle and it charges while you drive. Well, that's the dream anyway. The reality may not be quite so simple.

Lets assume for now that we're talking about the Nexus 4 which is equipped with the "qi" (pronounced chee) standard and lets assume that because all qi certified devices are (supposed to be) tested to work together by an approved lab that there's no reason not to think that's the way it will work. Well, no surprise, that's not the way it works.

Yes every qi receiver will charge from every qi transmitter assuming that you can physically line up the receiver and transmitter with each other. But given that the receiver (the part inside the rechargeable device) almost never has its exact location marked where you can see it, that can (at times) be difficult. And of course sometimes shape or physical construction makes it impossible to line up the receiver and transmitter depending on the devices.

The best solution to this problem is (in my opinion) the Panasonic QE-TM101 which actively searches for the receiver and aligns the transmitter with it in order to charge (search QE-TM101 on YouTube.com to see what I mean). Other transmitters can be hit or miss (as can be seen again on a number of YouTube videos). You can buy cheaper qi chargers (some for literally half the price) but without the convenience of simply putting the device on the pad and walking away, they may not be worth it. The QE-TM101 can charge 2 devices sequentially (put 2 devices on the pad and it will charge one and then the other) and is typically only available from Japan (a small plus is that the Japanese plug that comes with this fits into and is properly rated for a Canadian electrical outlet).

Notably, some other devices (like the Energizer Qi Inductive Charger and the ZENS Wireless Charger) combat this by placing multiple coils under the charging surface to allow a larger area for receiver's coil to line up with one of the transmitter's coils. Having not tested either of these myself, I am simply taking other's words for it that these solutions work well providing a reasonable effort is made to place the device near the known center of the coil array.

Wireless charging in the car on the other hand is a whole different ball of wax. As hard as qi wireless charges are to locate, qi wireless car chargers are virtually impossible to locate. In my searching I have managed to find only 1 currently available at retail (although Nokia is set to launch one any time now). The Owl CarPad/G is available directly from the Korean manufacturer but you'll want to be certain it's going to work for you (as it will probably cost as much to ship back as it did to buy). I should note here that this charger is "qi compatible" and not "qi certified".

They seem to be currently modifying their designs to fit various devices (as more devices are released it's harder and harder for them to ensure that their coil lines up with the coils in the various devices). They are also taking a slightly different approach to their charging logic for the car (as opposed to home chargers). They feel that most people charging in a car are also probably using the device (as a GPS or music player or bluetooth connected accessory) and have concentrated on charging based on that. The difference being that this type of usage puts strain on the battery and causes it to heat up. Applying an essentially uncontrolled charge through the coils (which will also heat up and are virtually always in contact with the battery) will produce too much additional heat and shorten the life of the device's battery. To combat this, they have specifically tuned the charger to avoid overheating the device. In some circumstances this may mean their charger stops charging (or fails to provide an adequate charge) in an effort to balance the battery's health with its charge state. Typical wired charging does not produce the same heat as is produced with inductive charging and would be less likely to have the same adverse effects (that's why this is not an issue with a wired charger).

Typically, the Owl Carpad Wireless charger will not charge your device to 100% and does not turn back on once it has completed a charge cycle (it will not trickle charge or keep your device topped up to full). Another pertinent note about the Owl brand wireless chargers is their unique ability to charge not only qi compatible devices as well as their own proprietary receivers, but they are also compatible with the fairly well established PowerMat brand of wireless receivers as well.

Wireless chargers in general base there charge level on feedback provided by the coils used to do the charging. As such even when properly tuned, these devices typically do not use your phone's (or other device's) internal charging circuitry and may not charge your device to 100%. Wireless chargers also do not typically "trickle" charge your phone once full (although some do) instead leaving it for a notable drop in power before they restart (if they restart at all). So if you use a wireless charger to charge your device overnight, don't be surprised to wake up to a device charged at 95%.

The (as yet unreleased) Nokia wireless car charger appears to be very precisely fitted to match their Nokia Lumia 920 (and the Lumia 820 replacement back) and will probably not line up well with many other qi devices.

I have had the opportunity to use 3 wireless chargers, so I'll give them a quick review and follow that with some test statistics (test all 3 devices in similar circumstances).

REVIEWS

Panasonic QE-TM101 (qi certified charger)

[QE-TM101 Pic]There are really only 2 reasons to use wireless charging over wired charging . . . convenience and the "cool factor". And the Panasonic QE-TM101 has both (in spades). How do you review the coolest device of its kind?

Well, it's the only charger I have seen on which you can place the phone virtually anywhere and it will charge. A charger simply could not be less particular about where you place the device. Put your phone (or other qi compatible receiver) anywhere on the charging pad and the charger will move its coil to match the position of the receiver and begin charging. If you have 2 devices, place them both on the pad and they will be charged in sequence (if you want them charged in a specific order place the first on the pad and wait for the charging to begin before placing the second device on the pad). It can only charge 2 devices in this fashion. The only real caveat is that the receiver coils must be completely on the charging area "somewhere" but that's a LOT less precise than virtually any other charger.

So that's the convenience factor. How about the cool factor? The coil (as it moves) lights up so you can watch it move to your device and watch it move between devices as it completes charging each, or watch it park when you remove the device (or when no more charging is to be done). If thinking that's cool makes me a geek, then fine... I'm a geek, and that's just cool.

That leaves "How well does it work". Well, each night I place my phone on the charger and the coil moves to, and charges, the phone. When it does so, a little blue LED in the upper right corner lights up to indicate that charging is happening. Notably, I used to fumble in the dark trying to orient the MicroUSB plug correctly without turning on a light so as not to wake my wife. The charging process does not take the full 8 hours that I sleep to accomplish, so at some time during the night it reaches a full charge, the LED turns off, the coil stops charging, and docks in the corner. Typically when my alarm goes off in the morning the phone is at about 95% charged. This is generally good enough (since I also have the charger in the car) but if for some reason I want a full charge, I pick the phone up turn on the screen for a moment and place it back on the charger. It then proceeds to charge to full (usually by the time I finish my morning caffeine infusion).

As with all wireless charging there is some heat as a result of the process, although I do not find my phone to be overly warm after charging.

Okay, I'm biased, but, the only way this device could be better would be if it trickle charged to hold the charge at 100% (although it's easy to understand why a wireless charger would not be designed to do that).

Owl CarPad/G for the Nexus 4 (qi compatible charger)


[Owl CarPad Pic]This is my quick review of the Owl Carpad/G (the one for the Nexus 4). First, it arrived in just over a week (from Korea) so the shipping was superb. It came in a nice retail package containing the charger, an 8mm clear plastic spacer, the suction mount, self stick disc and a manual. The manual (in 2 languages - English and I assume Korean) very briefly explains the product and warranty with some nice pictures but says nothing about the 8mm spacer. One very nice feature is that the LED light is also an on/off switch in case you find yourself wanting to reset the unit or turn off the charging for whatever reason.

It should be noted that I am not a fan of windshield mounts and so have no definitive opinion about the included mount except that it appears to be a genuine Arkon mount and if it is, then the quality should be very good. In my car I prefer a vent mount. I ended up purchasing a vent mount at a local retailer (if you don't mind the wait, you can get one from China on eBay for about $2.00 - vent mount with 17 mm ball, usually used for Garmin Nuvi products).

The Owl Carpad is not a good product to use with an unmodified vent mount. The plastic side clips are not nearly as rigid as they appear to be (which is a good thing) and they hold the phone nicely. While they haven't yet left any marks on the bumper as a result of putting the phone in and out of it I do expect their to be some wear as I prefer to slide the phone in and out (I'm the type of person who leaves my brand new phone in the box until the screen protector arrives in the mail). That is precisely why the traditional vent mount doesn't work well. The clips do hold the phone well enough that if you attempt to slide it out of the mount it will move around (since vent mounts are typically not rigid). I solved this by anchoring the vent mount behind the vent, but this is no reflection on the charger itself and may work better with a different vent mount or in a different vehicle.

Once you have it mounted you will notice that the charger cord sticks out of the bottom. Oddly enough, every time I saw someone comment on this I thought how petty and unnecessary it was. The truth is, the charger sits far enough from the vehicle surfaces that it really would have been nice to have had the power cord come out of the side or the back or even with a 90 degree connector. That said, I'm sure I'll get used to it.

So you set it up, you put it on the mount, plug it in and you're good to go. As mentioned I expected the side clips to be much more rigid than they actually were, so the phone slides in and out relatively easily (if the mount is solid), and snapping it in and out works well too (although I might be a little weary of the bending that thin, hard plastic in very cold weather). A quick aside. I point out that the side rails are flimsier than expected not as an indication of their being cheap, but rather because in the video reviews on Youtube and in the pictures they actually appear to be very rigid thick plastic when in fact they are thin and easily movable. The phone sits in it nicely and the clips hold it both in the mount and against the back for charging). When you first turn it on (press the LED if it's not already on when you plug it in) the LED flashes alternately between red and green and then settles on red (if it's charging) or green (if it's not). If disconnected from power, the unit will always be ON when power is supplied (this is an electronic switch, not a physical toggle) so don't turn it off and expect it to still be off when you return (if the power is interrupted when you shut off the car for instance).

You place your phone in the Carpad and (if it's on) it begins to charge. The process creates a fair bit of heat (I hadn't noticed this much heat with the home charger, but I rarely if ever pick the phone from the home charger prior to its completing its task). In either case the heat is not unbearable and not unexpected. I generally don't use my phone as a GPS and therefore tend to use the charger to top up my phone midday. But I did take it for a 30 minute scoot with the GPS on. The charger fully charged the phone with the GPS running (which was very close to full when I started anyway). The noteworthy point being that it did not drop in charge level during the trip. The charger became warmer than I might have liked and I certainly won't be directing heat out of my vent when I'm charging the phone (although I will be happy that I can blow the AC on it directly when the weather is warm).

You'll note that I haven't mentioned that little 8mm spacer. That's because the first thing I did was to remove the spacer since I fundamentally disagree with the process it is designed to allow. The spacer is designed to lift the phone away from the center of the coils so that the charger can still charge the phone but the feedback which would normally cause it to shut off when it gets too hot is avoided. This allows your phone to get hotter than (I think) it should, so that you can use high drain processes for prolonged periods of time. I am of the opinion that heat is bad for the phone (the battery in particular) and that systems designed to be shut down at a certain temperature should be allowed to shut down at that temperature. But... Owl wants to sell their charger, and this is an option many people want. Most notably, the most likely place to hear about the Owl CarPad (other than on their website) is XDA-Developers and people who frequent that site are more likely to push the limits of their devices so it's not unthinkable that a company generating sales there might be willing to bend a bit to sell to this crowd (who generally understand their devices a little better than most people do).

So the Owl Carpad does what I expect from a wireless car charger. It delivers a charge without the hassle of me trying to line up the plug with the little microUSB port. It delivers enough of a charge that I can use my GPS while charging and still not lose charge. And although it does get a little warm in the process, so far not warm enough to be a concern (but summer's not here yet either). It's a black device and since most people will mount it to the windshield or on the dashboard deck (using the included suction mount), it will be a heat attracting device, in a heat concentrated area, producing heat itself.

It does what I ask of it, but apparently I'm not very demanding. I need it to charge my phone between destinations. I don't need it to charge my phone while I stream music and use the GPS (with the screen on full brightness) while typing on a bluetooth keyboard. If I really need to do all that stuff . . . then aside from wondering why I need to do all that in my car, the feet on the bottom of the carpad do not block the MicroUSB port and the led light on the carpad is an on/off switch. I can always connect my MicroUSB charger (stored in the glove box or one of the many other compartments) if I need it.

The Owl Wireless Charge Pad (qi compatible charger)


[OwlPad Pic]I ordered this as a package deal with the Owl CarPad/G reviewed above. The Owl Wireless Charge Pad is a straight forward slab like many of the available qi chargers. It is available in black or white (I have the black one). There's nothing special about its looks, it just a black slab with a circle on the surface to show where the coil center is (I assume). It has an LED that changes from Red (charging) to Green (fully charged) and a Korean power supply with an adapter to allow use in North America (given that this product was never actually intended for North America, I can forgive that). The Pad itself is just slightly larger than a Nexus 4 which makes positioning the Nexus 4 fairly simple. You put the Nexus on it in about the only place that makes sense and it charges (if you rotate the phone 180 degrees it doesn't charge). I should point out that the Nexus 4 without the bumper fits in this pad like they were made for each other (unfortunately I use the bumper).

I don't know if it's coil placement or something else, but this charger does not seem to charge as fast as either of the other chargers (which is odd since one of the other chargers is also an OWL product which I would assume has the same coil). This may come down to positioning the device on the charger, but to be honest, I have a big black slab and when I place my phone on the big black slab in the position I expect it to work in, it charges... So I'm not about to play with it to try to find the "sweet" spot. Note (added later) removing the bumper from the Nexus 4 significantly increases the charging compatibility with this device - This charger charges the Nexus 4 very well without the bumper (and presumably a case would cause the same depreciation in performance as the bumper does - but that is simply speculation).

One advantage to this pad is that it also charges OWL sleeves (available for a number of smartphones) as well as PowerMat products. So plug it in, put your phone on it, it works. Pretty underwhelming actually, but it works nicely on my desk when I just want to set my phone down. Honestly though if this were my only charger, I think I would be disappointed. But before you take that to mean "don't get this", that's not what it means. This charger has one very significant advantage over a number of the chargers that I saw on Youtube. IT WORKS.

Typically if I charge on it overnight, I wake to the phone charged around 95% (the same as the Panasonic). If I didn't use the bumper (or a case) I would likely be very happy with this charger. You just put the phone where you think it should go and it works (with or without the bumper). After watching far too many youtube videos of people trying to figure out the sweet spot on bargain priced chargers, don't underestimate the value of that singular property.

TESTS


I put each of the three devices above to 2 simple tests. Also, due to poor test results with the Google Bumper on my Nexus 4 with the Owl Wireless Charge Pad, I redid the tests with the bumper off (for that charger only) to see if it worked better. All other tests were performed with the Google supplied Bumper installed.

Test #1 - Under Load

Charge the Nexus 4 for 20 minutes with the GPS active (running Google Navigation), a 20 minute timer running and the screen on.

Device Starting Temperature Ending Temperature Temp Change Starting Charge % Ending Charge % Charge Change

Owl Wireless Charge Pad

(Without Bumper)

29
35
+6
90
94
+4

Owl Wireless Charge Pad

23
29
+6
82
80
-2
Owl CarPad/G
26
34
+8
76
77
+1
Panasonic QE-TM101
28
36
+8
83
90
+7

Test #2 - No Load

Charge the Nexus 4 for 20 minutes with a 20 minute timer running and the screen off.

Device Starting Temperature Ending Temperature Temp Change Starting Charge % Ending Charge % Charge Change

Owl Wireless Charge Pad

(Without Bumper)

28
29
+1
82
90
+8

Owl Wireless Charge Pad

29
28
-1
80
84
+4
Owl CarPad/G
34
32
-2
77
85
+8
Panasonic QE-TM101
27
31
+4
85
96
+11


Now to be fair, no effort was made to match the test conditions between devices (time, ambient temperature, starting charge level etc.) but the result should still give a relatively good account of the charger's worth. Also with the 2 home chargers, the GPS was active but not being moved so no tracking was done, but the Carpad test was performed while driving with Google Navigation directing me (also the car was a little cooler than the house during the tests).

Conclusions


The Owl Wireless Charger Works much better with the Nexus 4 without the Google Bumper.

The Panasonic QE-TM101 consistently delivers the highest charge.

The Owl CarPad/G outperforms the Owl Wireless Charge Pad and delivers respectable on the go performance (with the bumper on).

Post Script


The Owl Carpad has been getting mixed reviews on the XDA-developers site. In reading through most of the "complaints", it's clear that the purchasers have the same expectations of the wireless charger as they do for their wired chargers. I tend to think differently than many of them.

Wireless charging uses induction. Induction creates heat as a part of the process. If you use your device (especially GPS and streaming data), this will also heat up your phone. You should not expect a wireless charger to charge your phone (or other device) as efficiently as a wired connection. If you're using the device during charging, the heat and use at that time can dramatically affect the ability of the charger to keep up. Wired chargers (typically capable of delivering 1 Ah to the device) can usually keep up with this demand and add relatively little heat. A wireless charger on the other hand will typically charge at a rate of 400-500 mAh and produce a reasonable amount of heat at the same time.

I want a wireless charger in my car so I can drop my phone in the cradle while I drive from point A to point B and get a little charge along the way. While I would certainly like to be able to use my GPS and Bluetooth and stream music while I'm charging, I honestly don't expect a wireless charger to handle that load without increasing the heat beyond a level which would be acceptable for wireless charging. If I'm going to do all of that, then I'm going to plug the phone in and charge it with the wire, or I'm (at least) going to accept that wireless charging has it limitations.

As an example, simply activating the GPS on my phone, typically increases the current draw by between 300 and 600 mAh. A Wired charger can easily compensate for this with very little heat. A wireless charger will be working at full capacity simply to make up for the draw introduced by the GPS and would be hard pressed to charge over and above that (unless the amount of draw required by the GPS dropped as well). It would however create heat and combined with the heat created by the use of the GPS it could cause the charger to cease charging (in order to keep your battery healthy).

It should also be noted that if you order the Owl Carpad/G for the Nexus 4, an 8mm spacer is included with the carpad. The purpose of this spacer is to give you the opportunity to bypass their logic. If you use the carpad without the spacer it will charge as intended and shut down before the phone gets too hot. If you use the spacer, it will offset the coils enough that it allows charging to occur (at a reduced rate) but the carpad will not as accurately sense the heat, thus allowing the phone to get much hotter before the charging stops. Virtually everyone agrees the phone charges better without the spacer and some note that using the spacer with a bumper or case on your phone may move it too far out of alignment to charge.

I guess what I'm saying is that if you keep your expectations reasonable for the circumstances, you are much less likely to be disappointed. If you really need the same results that you'll get with a wired charger, then stick with the wired charger.

As of now I've seen no reports of issues related to the car's internal temperature. But since that has a direct relationship to the phone's temperature, it will be interesting to see the effects of a hot summer on the state of wireless charging in the car.