Engine Bogs Down When Using Electrics

[mrHman]

Hey ppl...Need help addressing this issue in my mk1 focus 1.6...whenever im sitting still with engine idling and turn on any sort of electrical device e.g. rear screen heater or even rolling up auto windows. The engine will just bog down and grumbles like its low on power.....I was thinking about changing the battery or alternator but cant decide what would be best. I still have the standard focus battery in if that helps.....any ideas?

[artscot79]

any garage will do a free battery and alternator test ide d that first it may be a faulty battery cell or just a worn out battery before spending a penny have the free test done