Our battery problem is solved for now:
1. Failed dc/dc charger that floats 14.3-5 Volts on battery when car is started.
2. The culprit for the battery drain was a high amp fuse!! It caused the charging voltage to drop to 13.5 V (no alarm but there should be one) and to drain battery when car is off
3. No battery low or charging system alarms to tell you.
As soon as it failed it told the dealer not to just replace the battery but figure out what caused it to drain. The fuse was the difficult one. An infrared camera might have picked up the hot element. I told them to follow the current to the component that was draining the battery. It took 2 weeks but we are working again and enjoying our C-Max.
Ford still have to fix the NO ALARM problem. Until that is fixed we will run a volt meter in the 12 V socket to monitor the battery/charging system. This should be part of the standard instrumentation ofthe car.
You may have another cause but I suspect this fuse problem is causing a lot of batteries to fail.
IMHO the battery is NOT the problem but the symptom of something else not working properly. If you monitor the charging system via the 12 V plug or use the ETM you can check if your charging system is working. ie 14.3 V + and not below the 14.0 value when running. You can try to check the green light on the battery after a trip to see what color it is. Red is not good, black you most likely need a new one.
My wife and I love this little car. Now we must get Ford to fix the alarms via IMHO a software programming error of a set point of 12.0 Volts verse 13.0 V and please put a voltage meter on the dash board instrumentation. ie just like the ETM will be fine. I don't want to have to drive in ETM all of the time.
21 Nov 2014
Two weeks and all is well. Still awaiting the battery monitoring system update. No more battery problems so far. suspect fuse link may be defective which caused our problem.
I would have loved to give a better explanation but ford did not give me the proper part name. Just that it has very large cable size around 4-6 which is huge. We were told that we would be receiving a report in the mail but nothing so far. Must send a letter to ford.
19 December 2014 Still working great. Using a voltage meter to monitor charging system. Wish it was put on the dash as part of the instrumentation cluster
Edited by kaptnk228, 19 December 2014 - 01:13 PM.