Just the side panel to gain access to terminals.
The side panel tucks under the seat though...so depending on how much you wish to wiggle stuff around, and how tight your fits are, it might be easier your first time to remove seat first, then remove side panel.
Once you know how those two things fit together, you'll see how it can be done without removing seat.
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2008 WR250X
Gearing: 13t - 48t
Power Commander 5 / PC-V
Airbox Door Removed - Flapper glued - AIS removed
FmF Q4
Bridgestone Battlax BT-003rs