2000 V70 T5 Low Battery Voltage Message

[Laptoploon]

Hope someone can help with this...

Driving my granddaughter to school this morning, and the little red triangle popped on and 'Low Battery Voltage' appeared in the message window.

Got her to school OK and on arrival, turned the engine off and immediately restarted - no message.

Was at the school for maybe 20 mins, started the car - no message.... 4 miles down the road, up it pops again. Stopped for petrol, started the car - no message.... once again, 4 miles along and it pops up again.

During all this all the electrics seem to function as they should but I did try and shut off everything I could, including turning the light to sidelights.

When I arrived home I left the car running and metered the battery 14-15 volts - turned it off and metered it again - same. Did three false starts to try and drain some juice out of the battery, same meter reading.

Thoughts please..?