Default S5 not liking certain chargers?

My S5 does not seem to like certain chargers that previously worked (and still do) with my S4.

It will give a beep when plugged in and the light will indicate charging but then it will randomly beep again as if being unplugged and plugged in again. If I have the screen active, the indicator will go from the lighting bolt indicating charging to the normal discharging indicator and then back again.

I have tried different cords as well to no avail.

This also happens with a power bank battery that will charge my s4 with no issues.

The official Samsung charger works flawlessly of course, as doe an old Treo charger that I have.

It is not a current thing because I check that with the Galaxy Charge app and it shows more than adequate current.

Does anyone have any thoughts other than the obvious (using only Samsung chargers)?

Thanks