Thanks for bringing this issue to our attention via the community. And thanks@NTran for the great troubleshooting tips.
Kindly be advised that Samsung Galaxy C5 supports the Qualcomm Quick Charge 3.0 charging and Galaxy Note 5 supports the Qualcomm Quick Charge 2.0 charging. If the PowerCore+10050mAh battery you have on hand is QC2.0 version, then it will only fast charge your Note 5 instead of C5. To quick charge your C5 phone, you have to use our PowerCore+10050mAh Q3.0 battery. The QC2.0 version will only charge it at a normal charging speed.
I hope it helps to your concerns. Have a nice weekend!