Got back this morning from a week in the sun, only to find that the battery on my car was almost completely dead. The parking company (at Gatwick) got me started and said that it's a very common occurence, particularly with new batteries.
The guy told me that the unusually high number of flat batteries had prompted an investigation by BAA which found that the problem was caused by the high levels of EM radiation in certain areas around the airport. Alarms and immobilisers are also affected.
I can understand how poorly designed alarms/immobilisers/ECUs etc. are affected by EMI, but batteries?
The only thing I can think of is that the EMI was causing lights or other circuits to be switched on but there was no indication that the alarm had been activated.
Ideas anyone?
Kevin...
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EMF can not in itself discharge a battery. It can theoretically affect the things attached to the battery and its possible I suppose to make them electrically unstable and use current.
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Moral - carry a spare battery when you have to leave the car for long periods.
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The spare would go flat too, under the situation described, and you couldn't take it on holiday with you as it is a dangerous cargo.
Also, one week is hardly a "long" time for a car battery.
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True, but I thought the theory was discounted that it was pure electromagnetism alone, and more likely the things connected to the battery causing the drain. If the car's immobility sensors are constantly being activated, I suppose that could be enough to flatten the battery.
I assumed the car was being left behind, not taken on holiday, so there would be a nice fully-charged spare battery waiting in the boot on return.
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2 much easier suggestions.
1. Carry a set of jump leads (lighter and safer than a 'new' battery).
2. Disconnect the battery when you leave the car. Worried about losing your radio code/alarm etc? Don't be, as a flat battery means that they're both immobile anyway!
imho, I cannot believe that anything other than fairies at the bottom of the garden can cause a battery that's not connected to anything to go flat rapidly. I suppose I can believe that 'electromagnetism' - whatever that is (don't answer that one! I know exactly what it claims to be) - might drain a battery by causing strange effects on appliances attached to the battery.
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Batteries don't always go flat when left at the airport for a week. So disconnecting it before you go seems a rather silly idea - then you're going to guarantee having to reprogram the radio and faff with the immobiliser. I've left cars at airports for weeks and never had a problem.
Why not just take advantage of the free jump start service advertised at many airports?
Cheers,
Mark
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...not as silly imho as £75 for a spare battery that will only go flat at the back fo the garage!
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You have obviously got something causing a drain on the battery. The busines of EM radiation is a figment of someone's imagination.
I went on holiday for three weeks some years ago and left my brand new Calibra in the garage at home. When I returned the battery was flat, which it was due to the alarm. One week doesn't seem long enough to cause your battery to discharge so much, but it could happen if you had driven to the airport with numerous bits running on the car at the same time, e.g. heated rear window, wipers, headlights, blower motor. Thus, your battery would have been discharged somewhat, and leaving it with the alarm running for seven days would have added to the problem.
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I parked in heathrow a couple of months back and was surprised
at the amount of people that knocked into my motor ie causing the alarm to go off.my car wasnt the only one several were going at the same time..although not having the same tone.no one around to find out why.in the two hours I was there I found or rather caught I family opening all doors of their car and knocking into my car/and opposite them lucky I have door rubber strips but it had set off alarm.although that should not over a week cause total battery failure.may help.I would unless you regularly leave it for around a week without a prob put it down to one or several cells of battery gone.unless a drain is on battery is evident?
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Concorde used to do an excelent job of setting off car alarms when taking off...
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Batteries going flat on cars left near airports:
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Modern cars take current from the battery even when it looks as though all is switched off. My own car takes 0.065 amps. Less than a tenth of an amp.
Not worth bothering about, you might think. But if you do the sums you find it is able to flatten a fully charged 40 amp-hour car battery in 26 days. That is, 13 days for a half charged one.
When the car senses the key, from a few feet away, the current goes up about ten fold.
Radio transmitters and radars are able to cause electronic equipment to take current. How much current depends on the equipment design, the wiring it uses, how the wiring is laid out, what radio frequency is involved ---- it has a much greater effect when it causes the wiring to ring up ---- but also how far away the transmitter is and how much power it transmits. Quite complex for the non-technical person to understand, and even a lot of the 'technical' ones are less understanding than you might think.
The radio power in the pulses being sprayed about by the airfield radar is in the many kilowatt range and it can be very difficult to keep such pulses from getting into electronic equipment.
Cars will have been put through EM tests during their development and measures will have been taken to reduce/eliminate sensitivity to EM. Particularly in regard to the critical bits, braking etc. But there are other less critical electronics where an extra bit of drain may have gone unnoticed. And two cars are never quite identical. And what about minor production changes?
One way to investigate whether a car is subject to current drain EM effects is to go to where this is claimed to be happening and see if the battery drain can be seen to increase. As you can seen from above, even a tenth of an amp increase is going to have a dramatic effect on the life of a battery left standing during a 14 day holiday.
The problem is such tests can get very involved with test gear being used at various places, to try and find the bad spots etc., and are likely to need the cooperation of the site manager,
and probably the sponsorship of someone like the AA.
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Yes, probably a similar effect to that seen near to the Flyingdales military place in Yorkshire, people have been having terrible problems with cars switching their own systems on randomly, probably hall-effect or time ICs that only need a tny current to trip them on, well, this is easily induced in the circuits with a strong EMI.
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What test gear would you use that would require the cooperation of landowners, police, army etc.? I'd use a pocket, hand-held multimeter, and take the fuses out one by one until I find where the drain is. Then you've immediately narrowed it down.
Silly question, but are you sure you didn't leave on the interior light, and that the boot lid was properly shut?
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First you need to find a place where it happens. So you might drive into several parking places and try each one but that is hit and miss and could take a very long time. Each time inserting a meter in series with the battery, preferably without breaking the connection and losing coding. Then taking the meter out ditto and driving to the next place.
Instead it would be far quicker and more informative if you had with you a spectrum analyser that showed what frequecies were present and in what strengths at the various places (together with suitable aerials that receive on all the frequencies of interest).
That equipment is expensive and would need plugging into a power point or you would need to use a motor generator. So you are into spending some money. Secondly you need to test the car placing it at various angles because it may be OK at one angle but not at another.
I suspect it would not be long before you attracted the attention of the security staff and you were given your marching orders.
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Yes, probably a similar effect to that seen near to the Flyingdales military place in Yorkshire, people have been having terrible problems
>.
People always thing it is Flyingdales. Actually it is Fylingdales.
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