Intermittent battery light

[ava]

Hi, me and my dad are trying to get the the bottom of a problem regarding my polo. When driving we are getting an intermittent battery light particularly when coming off of the gas. We assumed it was an alternator issue but my dad changed it today and there is still the same problem. We have also changed the battery and no change. We are now struggling as what to look at next.

Any help/advice would be greatly appreciated.
Thanks in advance, Ava