Rather stupidly I managed to leave my lights switched on in my 2004
Cooper when I parked up yesterday.

Only realised today after it started fine and had driven a mile or so and the battery warning light came on intermittently.

I switched off the radio and climate control to let it charge while I drove.

During my hour or so drive it kept coming on but I had no loss of electrics or power (ie power steering etc) except for the speedo, oil temp and fuel gauges blipping to zero once in a while.

Am I right in thinking the warning is triggering because the battery got dropped to a low charge and it will eventually be ok when I get back and cycle it through the charger/reconditioner or is it a bad sign for my alternator?

 

Try the charger first.