2010 Mazda SPEED 3 battery draining when engine is off
My son is away at school and left his 2010 Mazdaspeed 3 manual transmission with me. I've been driving it at least once a week but the battery keeps draining even when the car is off. First, I thought the battery was bad so I put in a new battery. But after a couple of days the battery would still be dead. I got a digital meter and tested the battery. It reads 12.70 when the engine is off and 13.85 when the engine is on. So the alternator seems to be working. So I got a trickle charger to keep it charged between uses. I charged the battery to 100% and then drove it for 30 or 40 minutes and hooked the trickle charger back up and according to the charger it was only at about 40% immediately after driving it. So then I charge it back up using the trickle charger to 100% and then unhook the trickle charger and in 24 hours with the engine off it's down to 30%. Any ideas??