Owon Oscilloscope Battery

I wanted a battery pack for an Owon PDS5022S oscilloscope, but didn't want to pay the $70~80 (yikes!) for the one that Owon sells.

Some poking around shows that the scope consumes around 1Ah, charges at around 8.5v 300mA when on AC power and turned on. The original batteries are rated 7.4v 8Ah. It looks like an ordinary 2S lipo can be used, so I gave it a try...