This sounds like it could be either a alternator/ wiring problem or a battery that is getting old or has a connection problem possibly bad earth. Could be an earthing/ wiring problem in general. The first thing I would check though if you can is that the battery has enough liquid in it. You can open and check even the sealed ones. Does the battery have the little viewing bit that tells you what condition the battery is?
Green for good etc.. Is this bright green ?
Start with the basics and work your way up if battery is good then check the connections are clean and tight and so on see how you go.
If it is between gear changes on hard acceleration/deceleration it is possible your battery is low on fluid!
Last edited by gibot123; 04-07-13 at 23:57.