W209 Visit workshop battery malfunction

[claggy001]

Evening all,
I haven't posted on here for a long time as my 2004 CLK320 has been behaving perfectly. however, this evening the 'Visit Workshop' battery warning light came on briefly and logged a malfunction. It occurred while accelerating vigorously and although it went out after a short time, it seemed to do the same each time I applied enthusiastic acceleration. Once home and stopped the malfunction cleared itself when I switched the car off and back on again.
Where should I look to start to solve this problem? The battery was replaced about three years ago when I first got the car. I can get the battery/ alternator tested by a mechanic friend with the appropriate kit.

 

[Auto-mobile]

Alternator possibly not charging enough under acceleration is my guess.

 

[Ted]

Fan belt slipping?

 

[alecmascot]

Check the alternator pulley clutch ?

 

[claggy001]

Fan belt slipping?

Thanks all for your helpful suggestions Having thought about it since this would seem a good place to start. Will also still check the alternator and battery are both ok.
Don't get these problems with my old Triumphs...

 

[Ted]

Motorcycles or cars?

 

[claggy001]

Motorcycles or cars?

Cars, built up the road from you at Canley
SJJ_0974 by mark_sexton, on Flickr

 

[Ted]

Ah - the Dolly. I used to love them.
17acr alternator was a pretty simple setup
My old Stag...

 

[claggy001]

Ah.. the Triumph Stag! Been there, done that! Lovely car, almost a Coventry built Mercedes SL. Don't spend as much time watching the temperature gauge with the Dollies though