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Unexplained Battery Drain

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I've just had my first encounter with unexplained battery drain on a 2010 reg S-Max Ecoboost.

Car was last used on a Thursday afternoon, and battery was dead by Sunday morning, registering just under 6V on a meter. The lights were not left switched or left on overnight.

The AA came over, and jump-started the vehicle - the battery started charging immediately at the correct voltage - the battery is receiving charge so it is OK, and the alternator is OK as well.

After about 10 minutes the AA technician turned the engine off - the lights, radio and other electrical systems appeared to switch off when the engine was cut. He then measured the level of ambient discharge/drain from the battery.

This was where it started becoming odd. While it can take some time for the car to shut down completely, this was what was observed:

- For about 5 min, the level of discharge remained at 0.4A for about 5 minutes, but every now and then it would spike up momentarily to about 1-2A and then stabilize at 0.4A

- After about another 3-5 min, the drain decreased steadily to 0.3A, then 0.2A and 0.1A after which measurements were stopped.

The AA advised me have the electrics checked out by Ford as they weren't sure of what the problem was.

Anyone has a clue?

It'll be helpful before I take the car in and end up paying money to diagnose where the problem lies - which Ford may not detect.



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sounds like something on the canbus network is not shutting down properly.


It's not an unknown problem afflicting early batch facelifts.

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