Clank noise and battery gauge
 

Sometimes not always I will start my truck and be idling through a parking lot or something and the truck will clank fairly loud and shudder and the battery gauge drops down and then goes back up. Is this a bad battery? It will also "cough" at idle a couple times without the battery gauge moving. I attributed this to the extreme cold we were having here in Ohio but it's 50 out right now and my truck is warm

Thanks

It's the grid heater cycling, drawing amps. Perfectly normal. The truck will shudder a little because of the extra load being instantly placed on it.