7 hours. why would that be? the ONLY thing I can come up with that makes sense is make sure it has a full charge. turn amp off, unplug charger and look at the color of the led, its a greyISH white. why do i say this? because when charging you should wait untill its EXACTLY the same as it looks when its totally OFF. You may have to look close, as it will remain a very dim .... er ... amber sort of color for sometime till its fully charged and is the same color as totally off.
hope that helps.
make sure you are using the same charger that came with the amp. each amp I have the plug in current is different. I actually labeled mine at the plug end with masking tape

to be sure.
using a different plugin I THINK could mess up the charge that the battery takes, or could be because the battery was tottally run dry then recharged?
I just now unplugged it at full change and will try to make the most accurate estimate of time. and it damn sure better be more than 7 hours lol [sorry]
It should at no time take more than 6 hours to get a full change, as per the "manual"
who told you that 70 was a typo and that the battery should only last 7 hours? thats BS man