Check the Negative (-) terminal clamp is tight
Open the 'Positive' (+) protective cover
Check the Positive (+) terminal clamp is tight. CAUTION If using a spanner to tighten terminal, be careful not to short it on the bodywork. Replace the cover
Check battery is generally secure, if loose, tighten the battery retainer
The battery retaining clamp position
Tighten if required, a 10mm socket or spanner is needed. Not too tight because you may damage the battery casing