DarrenAY07

Intermittent Battery Drain

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This one is starting to drive me nuts with my Fiesta, its an 07 plate 1.6 Petrol

About 2 years ago I went to it and the battery was totally dead...no biggie as the battery was 7 years old so got a new one. Same problem the next day on the new battery.

At the time I thought it was the bluetooth module, so pulled the wire on this and thought no more of it.

Recently though, same problem - dead battery sometimes - I removed the electric mirror fuse (as one was stuttering when folding in so thought it may be this staying live) but then it happened again, then removed the heated mirror fuse, but its now happened again.

 

Alternator has tested ok, no leak back, puts out the full voltage when running and can charge a battery ok, also I've not been able to find any obvious drain, the interior lights go out, nothing in the power socket. The intermittent nature doesn't help the diagnostic as it can be weeks before it has the same trouble. No aftermarket alarms or head units, plus the radio/dash display goes out after about 15 mins as expected. 

Does anyone have any other suggestions as what to look for? Apart from that its a nice low mileage car which hasn't caused me any other problems in its life

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I had a dead battery, just once. On mine I think it was a stuck a/c relay not turning off the fan.

 

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This is the one persistent problem I have had on my 59 plate Fiesta since new !   OK so I do a lot of short journeys but surely if everything was working ok it should last more than a week ? Battery will suddenly go flat without warning.   Several AA call outs while under warranty diagnosed the battery so the dealer changed the alternator !  After more AA call outs, the dealer changed the battery.  Car is now seven years old and I still get the problem.  I charge the battery every week to keep the problem at bay.  Surely I shouldn't have to do that ?  I have a digital voltmeter in the power socket to keep my eye on the battery voltage.

I have come to the conclusion that Ford skimped on the size of the battery (43AH) and it is not up to the type of use I give the car.  If and when I change the battery I will get the largest that will fit, maybe the size fitted the the diesel models.

Alan

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I'd expect it to be able to handle this unless the battery was in a poor state - a colleague of mine with a Fiesta only does a 3 mile run to work, and thats about all he drives and he's not had this trouble.

 

I think with my car a module or something is not shutting down (thanks Winemart2 for the air con suggestion but this doesn't work on my car it lost all its gas earlier in the year as I think something made a hole in a pipe or condenser), but the intermittent nature makes it difficult to find - plus if I disconnect the battery and then reconnect it, it doesn't drain which makes me think something is staying live until next time the ignition is turned on.

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That's interesting re your friends usage.  I regularly do several short trips (2-3 miles) during a single day which I assume is causing the problem but I still think a modern car should be able to cope as it has an alternator (as opposed to the old dynamo !) output and modern electronics.  The car was checked for a current drain  and it was ok. 

A staff member at another make (VW) franchise commented that for every time you start the engine, it takes around 8 miles to replace the energy used.  This sounds common sense to me.  How do cars with start/stop technology cope ?

 What is even more surprising is that my problem can still occur during the summer with little or no headlight use and warmish temperatures.  I can't wait for yet another winter !

As I said, the battery was changed by the Ford dealer right at the end of the warranty period (although I am not convinced it was a new one).  I even  try to avoid using the lights,heated screen etc.   I see all the newer cars with daylight running lights on (admittedly they are LED) and assume that their alternator must cope.

 

A.

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8 hours ago, Magenta said:

A staff member at another make (VW) franchise commented that for every time you start the engine, it takes around 8 miles to replace the energy used. 

They are being a bit pessimistic. A warm start takes 2 to 4 seconds of cranking, a couple of minutes of driving should be enough to recover that. A cold start, especially with a diesel & glowplugs, would take 2 or 3 times that amount.

With very short journeys, make sure it gets a run once a week or so, or an overnight charge, or use a solar plug-in charger.

 

On 13/09/2016 at 1:37 PM, DarrenAY07 said:

Alternator has tested ok, no leak back, puts out the full voltage when running and can charge a battery ok, also I've not been able to find any obvious drain, the interior lights go out, nothing in the power socket. The intermittent nature doesn't help the diagnostic as it can be weeks before it has the same trouble.

You seem to have been pretty thorough in eliminating all the possibilities!

I wonder if there is an intermittent fault in the charging. The 3 wires from the alternator, one to the fuse box, and two to the pcm. Problems here could make it fail to charge on occasions.

Like Magenta has, one of those cigar lighter fitting voltage displays ( a few quid off Ebay) might be a good idea. They are not very accurate, the system bus voltage there may not be the same as the battery voltage, but they will serve well for comparison purposes. If possible, compare the display reading with actual voltages on the battery terminals at a couple of different load situations (idle, nothing on, to 2000rpm & full winter running load of headlights, fan & wipers.)

The alternator should be able to maintain headlights, fan & wipers with 14.2 to 14.8 volts, certainly down to about 1500rpm.

Note: The Ford smart charge system can cut the voltage back a bit on a long run, and with a fully warmed up engine. But it should give full output for some time after starting.

 

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I've checked my plug-in LED voltmeter against a value measured with a Fluke meter under various conditions and it is within 0.1 volt which seems good enough.  On start up,( after recovering from the initial volt drop on starting which can go as low as 10.8 volts)  it will initially show about 14 volts for a couple of  minutes then dies back to about 13 volts during normal driving.  This seems fairly normal to me.  However, after being left overnight, say, the 'standing' voltage is usually only around 12.2 volts which seems a bit low.

When the AA tested it after a completely dead battery, the alternator was pushing out  a massive 30 amps momentarily which proved that the alternator was healthy (the Ford dealer still changed the alternator !).  It has become such a long standing problem (6 years)that as well as trickle charging the battery about once a week, I have bought a 'jump starter'to carry around in the boot as backup!

 

Alan

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37 minutes ago, Magenta said:

t will initially show about 14 volts for a couple of  minutes then dies back to about 13 volts during normal driving.

It seems like the pcm is cutting back the alternator output voltage too soon. Check that the engine temperature gauge works ok, the coolant temperature sensor is one part of the system used by the pcm to control alternator voltage.

My car system seems to maintain a little over 14v almost all the time while running.

Around 13.5v will maintain a battery at a charge level, preventing discharge, but to get charge into the battery in a sensible time, it needs well over 14v. Up to 14.8v for a silver calcium battery. The 12.2v overnight reading suggests the battery is being maintained at 50% of full charge, or less.

I think you said that both battery & alternator have been changed.

If it is the pcm, there is probably not much that can be done about it. Software updates, re-programming, testing are all Ford garage jobs unless you are very technical and adventurous. Weekly charging or a solar charger would be a more economical solution.

Alternator current ratings these days are in the 100A to 200A region, but testing an alternator to this level would be a specialist job.

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