I purchased the 18w A to C adapter along with the unit, I'm using the 1st bay but still can't get a protected 21700 cell to charge at anymore than 500mah? I've tried the last bay also, but no. And I've tried it being the only battery in the unit? I've researched it but haven't found where a protective cell will limit the charge rate, or is this my issue? Tks to anyone in advance! I hope im just over looking something!!