It would seem that there may be quality issues with the Opus BT-C3100 (v2.1).
My sample's issue was much more severe -
Slot #1 (leftmost) gave unrealistic/erroneous readings -
enough that I cannot trust it will not over-charge or over-discharge my batteries - so I would not use it at all -
with one of the important slots that can charge above 1Amp unusable -
if using slot #4 (rightmost) to charge at above 1A - the use of any of the other two slots (#2 or #3) reduces the charge in #4 down to 1A -
so effectively a 3-slot 1A charger (or 1-slot charger above 1A).
I opened a ticket with GearBest.com almost immediately with full description and photo evidence of the defect
(as described in posts
#55 and
#59 of this thread)
GearBest basically gave me the (polite and amicable) runaround -
Even after finally managing to come to an agreeable arrangement of a partial refund
without me having to return the defective unit (very expensive with tracking to China, and they will not pay for return shipping),
they did not actually make the agreed and promised partial refund,
and even asked inexplicably for evidence of the defect two more times.
It was not until today - after I opened a dispute at PayPal (where PayPal holds their funds) -
that the "offer" of the partial refund was made on PayPal.
I hope defective product is not the norm -
although I think the customer service is.