Ford Focus Dead Battery, again

In November 2006 I left my 2003 Focus for four weeks. When I returned, the battery appeared to be flat. I had the battery checked, and it appeared to be OK, but I bought a new one as a precaution. I
am now in Spain for eight weeks, and a neighbour has been starting my car weekly, letting it run to keep the juices flowing. All was OK until last Sunday, when he phoned to say that the battery appeared to be dead - a repeat of my November experience. I am no expert in these matters, but this looks like a random current that suddenly drains the battery in a week. Surely this would not happen unless something is left switched on, which it isnt. I am returning in three weeks, and would appreciate any advice. Thanks, Graeme
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You might want to check the under hood or trunk light, if equipped. Try disconnecting the ground cable over night, to determine if the fault is in the battery itself. Better yet have a competent technician do a draw down test.
mike

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snipped-for-privacy@hotmail.com wrote:

How long has your neighbour run the car for?
Modern cars do have a significant idle battery drain; the ECU memory, alarm system and even the radio consume small amounts of current all the time the car is parked. Many will run down in two weeks.
Starting the car will also obviously use some more. If the car was only left to idle for 10 or 15 minutes, it would have done more harm than good.
If you intend leaving your car for long periods fairly frequently, you might want to invest in a special type of battery charger designed for this purpose. You can leave it connected all the time you are away.
The cost of this might be less than the cost of regularly relacing your battery; the life of vehicle batteries is seriously compromised by being left after deep discharge.
Chris
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There is obviously something wrong with your cars electric system. A car battery should last at least 6 years as rule of thumb, even under bad conditions. I'd let check how much current the car uses if anything is switched off?

Depending on the temperature self discharging might well be higher then this.

Untrue, the Focus three-phase alternator is well capable to deliver enough energy for almost all electric equipment together, even if the engine is idle. With one exception, the heated windscreen needs about 1000 rpm or it will suck the battery empty.
Ever used a clamp-on ammeter to see how much Amps three-phase alternator can pump into a battery even on an idle engine if the regulator demands?

Seconded, though you can save quite some money on your electric bill if you use a timer and run it for 1-2 h daily. If you happen to get one of the better ones.

Indeed.
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Michael Heiming wrote:

Read what the OP has written. He left the car for four weeks with a flattening battery! No car battery will last for six years if treated like that; they are not designed for, and will not tolerate, being left after deep discharge.
Also note that the OP said the original battery was replaced after the first incident *as a precaution*! It may not have failed prematurely at all!
I'm willing to bet the OP has *no* problem with his cars electrical system at all.

Absolute rubbish! The drain of modern cars when not in use is so high (when compared to vehicles of the past) that some manufacturers are having to arrange for software to shut down things like alarms and keyless entry systems after a couple of days. Have a look at the specification of VAG group cars.
I've seen a "new" battery that had a manufacturing date of six months ago start a car easily.

Why do you specifically mention "three phase alternator"? All vehicle alternators I've ever seen are three phase! In fact, old British motorcycles of the 1960's used three phase alternators!
Assuming the OP's vehicle is petrol-engined, his alternator is capable of an output of 80 Amps. This would not be available at tickover of course. However, that output would only be used to balance the demand; there is no way that the system would charge the battery at that rate! It would boil before it was full charged.
The highest charge rate I've ever seen to a flat battery (*not* the total alternator output to the vehicle), is 30 Amps. (This was on a much bigger vehicle than a Focus, ans was not achievable at tickover.) If you assume that the OP's near-flat battery was recharged for 15 minutes at 30 Amps, and his battery was a mid-range 60 Ah one, at best only one eighth of its capacity would have been restored. It is probable that the cold- start would have taken more than was replaced.
On the assumption the the OP's battery was 75% discharged, work out what current would be needed to fully charge it in 15 minutes!

No. I've only done it with a proper ammeter. A clip-on of the type typically used to measure DC current is not a very accurate or reliable device.

Chris
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[..]
Strange, I have been working as professional car mechanic at VAG decades ago, we used a clip-on with a $$ Bosch meter for this sort of thing. Worked great!
Anyway the best idea would be if the OP would let some professional garage test his electric system, we can only remote guess here.
FYI The focus alternator provides 14V/90A as rule of thumb it should deliver 2/3 of this at idle engine, about 60A. Leaving the engine run for 10 minutes idle once a week with no or very few things turned on should be enough to keep it charged. Even if I agree there are far better methods to keep a battery fit.
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It would be good enough to give a guide as to whether an alternator was charging or not; it is unsuitable for anything needing accuracy.
I worked as an industrial electrical technician for over 40 years, and I can assure you that clip-on ammeters are not accurate. The place I worked for much of that time worked to medicine licence standards. It was not allowed to measure current using a clip-on if the results of that measurement would affect the product. We could only use them for rough and ready fault finding purposes.

Nope, the best idea would be that the OP found out how long his car had been run whilst he was away. If for less than 30 minutes/week or so, he should ask his neighbour to run it for longer next time. Better still, as I have said and you have agreed, buy a suitable charger.

Nope, the alternators for petrol cars are rated at 80A; only the diesels are 90A. An alternator won't "deliver" anything. It will respond to a load. This is much more likely to be around 50% at idle. It certainly will not charge the battery at anything near 60A; the regulating system controlled by the ECU would not allow it. What do you think would be the result if it did? Have you ever seen a battery that has been charged at much too high a rate?
Even given your values of 60A for 10 minutes, and assuming that the capacity curve was a straight line, (which is isn't), you would only replace one sixth of the batteries capacity. To try to say otherwise is to deny the laws of physics!
Chris
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[..]
You were certainly able to see what happens with an uncharged battery with it. Of course they can't be that accurate, but showed at least what you would expect from the numbers of the alternator, perhaps +10-20%. If it was OK.

I doubt the device you used was in the price range of the one I had used.

Seconded about a suitable charger, it is in addition much more ecologically then letting the engine run for 30 minutes idle, which is btw not even legal anywhere.

I do not deny anything, but the mere fact that it was just not run long enough. It should have been enough for just the single start needed. The OP mentioned he had already replaced the battery shortly on a 2003 Focus! Which makes me curious if there isn't some additional problem?
Sure it might be just frequent deep discharge, which is very bad for this kind of battery in any case. Again this leads to the suitable charger.
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Michael Heiming wrote:

I worked for the second largest pharmaceutical company in the world. If there was an item of test equipment that was useful to us, we got it...
Most of the test equipment was Fluke.
All of our equipment was purchased with calibration certificates; every instrument was re-calibrated annually. If an instrument needed to be opened to replace the batteries, it had to go back for re-calibration!

Where are you based Michael? It's perfectly legal here in the UK to leave a car ticking over. If it's on the street the driver must remain with the vehicle. If it's on private property, you can walk away leaving it running.

But that was four months ago, and as I have already pointed out to you, the OP only changed the battery "AS A PRECAUTION"! If a fault existed it would have been obvious long before now.
The battery would probably have continued to work perfectly well for a number of years.

Chris
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[..]
You might have gathered it from the .de in my From Address. [..]

Chris,
this is an educated guess, not more. It shouldn't hurt to let it have checked.
A suitable charger to keep the battery in good conditions is the way to go.
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This could be the action of the ECU self protection system that is being fitted to newer Foci. It is fitted to the Focus Cmax which came out in 2003 so it could be on your Focus The theory is that if the ECU senses the battery starting to get low , it switches on the headlights to make sure that the battery goes flat and has to be recharged on a charger rather than jump started. There is evidence that sometimes this circuit goes wrong and discharges the battery for no apparent reason.
I realise that this might sound strange but I have it on good authority from an auto electician who works for Ford.
You will find references to this on FFOC if you don't believe me!
Bob
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Evidently so.
You can't just start a car and leave it sitting, it wont charge the battery! All that has happened is that the battery has used significant energy to start the car, and it's not really doing anything, just idling. A decent drive once a week would be much more beneficial than your neighbour starting it every day.
Didn't you research this before you asked your neighbour to do it?
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Ride wrote:

Didn't you read the rest of this 9-day old thread before posting the same thing everyone else said?
Chris
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