Hi @kgreen747 ,
Thanks for bringing the issue to us via this post and email, and thank @all for good suggestions!
Please be assured that this PowerCore+ 26800 PD should charge your Macbook Pro 13’ just fine though at slower rate than the Apple supplied charger, as it only outputs 30W max. According to our engineers’ test, it will take about 3 hours for the mac to be fully recharged by the PowerCore+ 26800 PD.
Then how to use this Anker PD battery? Please make sure to insert the included Anker USB C to UBC cable via USB-C port, press the LED Power Wheel to activate USB-C output, then connect your devices to it to start charging. As a kind reminder, please make sure you lower brightness of your mac and don't be multi tasking to ensure it’ll charge properly, as @cdarienzo1 suggested.
Hope this helps. Should there be further concerns or questions we could address, please feel free to contact us via "email@example.com".