well I have responds all over the place, but since people do not use the search function and get the knowledge from an old thread they ask the same question over and over again. Check my help link below it will bring you to the most valid posts.
And now you can not recharge a 2 cell battery what is from 7 to 8V between high and low with a 9V psu.
You have some electronic in between what expects a certain voltage to operate properly.
and yes it shows a charging symbol because the circuit detects power but is is not in a valid range to operate correctly.
I would go with a 12v2a
why, it charges more gently and produces less heat = less problem of battery swelling
1981 soldered my first Sinclair computer 1K, tapedeck * 1984 build and sold IBM clones 8Mhz, 512K, 20MB HDD * 2018 messing with ultrabooks