I started my vauxhall movano for the first time in about 6 months today. I had to jump start it, it started up fine, but the battery light is on constant. Ive took it for a 5 mile run and its still on and its not holding a charge.

Does this mean that the battery is totally knackered? Or could this be something else like alternator maybe? Ive had knackered batterys before but none that have ever lit the battery light constantly.