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 the spanner on the bodywork!
Check battery is generally secure, if loose, tighten the battery retainer
To tighten, a 10mm socket or spanner is needed. Not too tight as you may damage the battery casing