Battery No Longer Powerful

Optima YellowTop battery since 5/07
Recently if I just play radio (engine off) for just under 10 mins, the car won't start. Is it because it's not being charged ? or is the
battery a goner - Is there anything I can do to revive the battery ?
thanks
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Normally my Z4 stays in the garage until the weekend. Then I started driving it every day to the P.O. and back (10 mrt). Then one day it didn't start. I took the battery to the parts store and they checked it out for an hour. It was O.K. Then I contacted the BWM shop and took it in. Again it checked out O.K. The mechanic asked about my driving habits. He said I had a bad driving profile. The battery would be drained a little during non-use and more upon start-up. I was not driving far enough to charge it back up. He said he has had this discussion with people who buy a new 7 Series and come back a month or two later complaining about a dead battery. Anyway, I bought a trickle charger for $70. I connect it and it "tops off" the battery every 2-3 days.
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In article

Never mind the battery - it kills an engine never getting to full working temperature. Which it won't in five minutes regardless of what the temp gauge says.
I have a charger bought from Lidl for 12 GBP. Charges the battery then switches to a maintenance charge which can be left on indefinitely. Small enough to just about fit in the pocket, but powerful enough to charge a flat battery overnight. Very handy for my other car which doesn't get as much use as my BMW.
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*Money isn't everything, but it sure keeps the kids in touch.

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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Measure the battery voltage with the engine idling. Measure the battery voltage with the engine and everything on the car turned off. Post the numbers here. --scott
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"C'est un Nagra. C'est suisse, et tres, tres precis."

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