Top critical review
Tricky to charge, but capacity as advertised.
June 12, 2019
First thing to know: This will NOT charge from a low-amp (500mA, or 1.5A, or 2.1A) source. It draws a hard 2.7A from the charger and if the charger's voltage sags too much under that draw, the Tenker unit will declare failure and refuse to charge.
Once I figured that out and threw my beefiest brick at it, it charged right up. Measured 39.58 watt-hours going into it, which is very close to the claimed 39.96 watt-hours in the manual.
Then I discharged it into a dummy load which was set to draw exactly 2.0A. Measured 26.56 watt-hours coming back out, for a round-trip efficiency of 67%. (This is fairly normal, since this internally uses a 3S stack of lipo cells, meaning that charging goes through a boost converter, and discharging then has to go through a buck to create the 5v output, and both of those have their own efficiency hit plus the batteries' own Peukert efficiency and other effects.)
The USB-C port is both an input and an output, which is a little disorienting. More than once, if I had my inline ammeter connected to the Tenker's USB-C but nothing on the other end, the Tenker would fire up and output power over that port, waking up the meter, but then when I plugged the other end into my charger, it wouldn't notice that and it would continue trying to output power, and all sorts of wacky behavior would ensue. The solution was to unplug the meter and let the Tenker fall asleep, then plug the meter into the charger, then into the Tenker, which then goes into charge mode and begins charging. THAT's why I gave low marks for ease-of-use, there's no way to force the USB-C port to be input-only, and since it's the only means of input, it can mean that you think you're charging the unit but you're not -- it's fighting with your charger over who gets to supply the power. If I didn't have a meter to understand WTF was going on, I would've been completely lost and frustrated.
The USB-A ports work just fine. I don't have any QuickCharge ports to test the QC functionality, but they output 5v beautifully.
Also, I still haven't figured out the purpose of the on-off slide switch on the side. Some functions seem to work regardless of the switch position...
This unit cannot do passthrough charging -- when the USB-C port is acting as an input and charging the unit, the USB-A ports are inactive.
The flashlight is obnoxious. You can't turn it off without cycling past SOS and strobe mode, and the SOS mode is so slow (roughly 1wpm in standard Morse cadence) that many people might not even recognize it as an SOS signal. If you set it on your pulled-over car in SOS mode, traffic could come around the bend, see a flash or two, and continue right on down the road, without ever realizing they were being signalled to. Also, the light is on the flat face of the unit, but the edges are round, so it's hard to stand the unit up in such a way that the light will aim somewhere useful. You'll have to prop it against "a rock or something".
The included jumper cables have an enormous lump that presumably contains some diodes and stuff. Older ones have diodes. This also has a little nearly-invisible button on the side which appears to control some sort of internal power switching; might this actually have FETs in it? There's also an LED which appears to be for polarity sensing. I'll come back and update this review when I get a chance to check this out more thoroughly.
I also haven't had a chance to test the jump-starting functionality. Will update the review if I do.