How do you know when the Hybrid battery pack is going.
I have a 2008 Mercury Mariner Hybrid. Original owner, with about 120k miles on it. My Hybrid battery loses all charge in cold weather if left over night or for a day or two. It then takes quite a while of idling or driving to take a charge. If then driven it will act normally (after taking a bit of charge) and charge up, but lose the charge again if left undriven in the cold. Does this mean that my battery pack is about at the end of it's life? In all reality, it's only an issue in VERY cold weather, and even though I'm in Colorado, it doesn't get THAT cold, that often. Thanks in advance for any help!