battery light help??

[hobbo]

when i got home today and switched engine off my battery light came on,even after pulling keys out etc and locking door the battery light still stayed on,i went back in and started engine and battery light went off as usual but then when i turned it off and left car it was on and i assume its still on now
is this is warning my battery's low??or faulty??

 

[Tom]

Most likely alternator fault.