Check the Negative (-) terminal clamp is tight
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 13mm socket is needed. Not too tight as you may damage the battery casing
Now replace the battery cover