The airpad power source is 5V. If I use 6.7volt, will it be problem?
Thanks!
Guess you overlooked it but I answered that in my response above in the first sentence.
A Snip from the referenced post
Not knowing how robust the charging system in the AP is and if it can handle over-voltage I would not exceed 5V
To add a bit more possible helpful data.
LiPoly batteries can be extremely dangerious. It is extremly unwise to use aftermarket low quality chargers with devices which have LiPoly batteries in them. Many of the laptop ,cell phone and other LiPoly powered device which have caught on fire were being charged with an after-market charger or using an aftermarket (non.OEM) LiPoly battery in them. Some LiPoly batteries have battery management / safety circuite / devices attached tio them , som devices have such circuits built in to them . Many aftetr-market batteries and chargers have little to not testing or safety checks at all.