The charger contacts are of very poor quality. In my case, I had to lift them a little to connect correctly with the battery pack. Conclusion: the light is now red while charging and green when charging is complete. When the base does not have the battery the lights are off.
My charger is faulty it is now showing a green light when I put in a flat battery to charge and will not charge it at all the rear slot only worked for a short time but this didnt bother me until now as i cannot charge the radio at all .. great radio poor accessories .. will be asking the seller to replace it ..