Help! Aerobike x-ride

[Montymod]

Just bought this ebike through Groupon for £770.
Enjoying it a lot but the battery carries this overweight 70 year old for about 20kilometres. Would like to get more out of it.
Where can I get another battery.
Montymod.

 

[Benjahmin]

Gonna need a bit more detail Monty. Some pictures of bike, battery and mount and/or a spec.

 

[Jonah]

Just bought this ebike through Groupon for £770.
Enjoying it a lot but the battery carries this overweight 70 year old for about 20kilometres. Would like to get more out of it.
Where can I get another battery.
Montymod.

Is it this one?