I just installed a brand new battery and plugged it into my Schumacher battery maintainer at the low current setting (3A) until it reached 100%. That was yesterday. I left the car locked in the garage until today. Today I went to check on the car and discovered the battery voltage was 12.6V and my battery maintainer said it was at 77%. So somehow it had lost 23% of charge overnight while parked and locked (so it would go to deep sleep). So then I took it for a drive and did 3 miles. When I got back, I tested the battery again and now it was at 12.4V and 59% charge. That seems excessive, right?
Can somebody please let me know if any of this is normal? I have take the car to the dealer and they were no help whatsoever and told me the car was working fine.
Battery drain
Is the car working fine? If it is, then I would suggest you try not to worry about it, use the car normally, and check on the battery in a month. Then perhaps check it after another couple of months, if you're still concerned about it. I certainly wouldn't expect a three-mile drive to put any charge back in a battery, quite the opposite in fact.