[Rasp]

I have had this happen before on cars. Usually on a winter night with the heater blowing the lights on and possibly the radio playing.

From what I understand this is an alternator issue. Your alternator is trying to keep up with the load.

As alternators age they are able to produce less and less current. Therefore you see dimming lights and slower wiper blades etc.

If you step on the gas you will see the lights brighten and the wipers go faster. This happens because your alternator is turning faster and therefore producing more current.