Some successes, some failures
Portable chargers for things like cell phones have been available for quite a few years now. What's newer is the PD charger; well, not so new: the spec is ten years old, but only in recent years has it become widespread. PD is short for "power delivery," and these portable chargers are powerful enough to recharge laptop computers through a USB-C port -- a port that my friends who reside on the other side of the Great Wall of Apple are beginning to learn about.
I was interested in PD batteries, because I now have two Chromebook laptops and an HP Windows laptop that are charged through USB-C ports. When I travel, I sometimes have no access to power:
- The commuter train in my neck of the woods has no power outlets
- Power outlets on airplanes are flimsy, with the plug continually falling out
- Conference halls might or might not have power outputs
The worst is the all-day conference, where my laptop lasts four hours -- no matter the brand or model. I take along extension cords on my trips and usually I can sit close enough to an outlet. Some conference organizers are nice enough to provide power in the press seating area; the most egregious was at an event in Las Vegas where I could only recharge my laptop at an outlet in the hallway during breaks, and where I had to stand guard for the full 15 minutes available to avoid having my laptop stolen.
So the idea of a PD recharger is attractive, and I purchased one last week: the 20,000mAHr Imuto X4G (see image at right, above). I like it because its ports are very clearly labeled (see photo at left), unlike most rechargers. Here are its output ports:
- USB-A 15W (5V - 12V)
- USB-A 18 W (5V - 12V)
- USB-C 60W (5V - 20V)
- USB-C 100W (5V - 20V)
- Trickle charge on all ports (shown on the display as ][ )
Note that 5V is the traditional USB voltage for charging older phones and most other devices that charge over USB-A ports. Maximum output on this particular power supply is 138W (even though the body is labelled 100W), so you can use, for instance, a 100W and an 18W at the same time. Trickle charging is important for charging devices slowly (which saves battery life), or for maintaining a full charge. To turn on trickle charging, press the Imuto's power button twice, quickly.
Modern devices are smart and can talk to battery chargers over the USB cable, so the PD standard allows several voltages, and the devices will react accordingly, automatically. Here is what the PD standard specifies:
- 5 volts at up to 3 amperes (up to 15 Watts)
- 9V up to 3A (up to 27W)
- 15V up to 3A (up to 45w)
- 20V up to 5A (100W); over 3A requires a USB-C cable rated to handle more than 3A.
More voltage and more amperage mean the battery is charged faster, which is important for large-capacity batteries, such as those found in laptops.
Remember that voltage is delivered by the power supply, amperage is drawn by the device being charged -- and that volts x amps = Watts. This is important, because just because a power supply says it outputs 60W (or whatever) doesn't mean it always does. The W output depends on what the device being charged wants, so hooking up my Bluetooth headphones to the power supply's 60W connector with a voltmeter shows that only 1.2W are being drawn -- that's all the headphones want.
For much more information about how the PD spec works, read "USB Power Delivery explained: What you need to know about ubiquitous charging" by Robert Triggs at https://www.androidauthority.com/usb-power-delivery-806266/.
Testing the PD Charger
But it didn't seem to work with my Window-based HP X2 convertible (tablet with removable keyboard). The computer complained that it was not receiving sufficient power (see screen grab at left), even though the specs of the Imuto matched the power requirements of the X2. This was a major disappointment, for I was looking forward to using this lightweight Windows computer on future trips, and topping up its battery with the Imuto.
So I went into research mode. Others had the problem with other chargers, so I knew it was a problem with the laptop. Most of the solutions involves "update the BIOS" or similar. Finally I found a "reason" from HP itself. It turns out that the "HP Smart Adapter" can be too quick on the draw, sensing a lack of immediate power and reprimanding the user that the supply is insufficient.
Using the USB voltmeter, I could see what is happening electrically. When asleep or in hibernation or turned off, the computer draws 5V and 1.8-1.9A. As soon as I press the power button to wake up the computer, the amps drop to zero.
In the end, I found no good solution to the problem. Charging while asleep is somewhat helpful, but then I can't be using the computer at the same time! I don't know if perhaps a different model of portable power would work; I don't want to spend the $100 to find out. So, major disappointment there.
Charging the Charger
The drawback to a giant portable battery, like this 20,000mAHr one, is that it takes a long time to recharge, after being depleted. So, I looked for a PD power supply that would output the most volts and and the most amps to the Imuto, using my USB voltmeter (see image at right). Over the last couple of years I bought several of PD chargers for use at home and on the road. I was surprised at what the USB voltmeter told me: most of the ones that claimed to output PD power did so at only 5V and 2.5A -- at least when recharging the Imuto.
As I worked through my collection, I found one that was speedy: 20V and 5A -- 8x faster. It is similar to this model: https://www.amazon.ca/Charger-Sisyphy-Adapter-Delivery-Compatible/dp/B08NKBFX26. I say "similar," as the unit I have has no brand name emblazoned on it.
A reminder that you also can use the power supplies that come with laptop computers to recharge portable power supplies, provided they have the USB-C connector. The ones that I have output 20V/3A to the battery, which could be a limitation due to the cable attached to the power supply (which does not support 5A current flows).