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Mazda-6 Cell Phone Drains Battery

Our 2008 Mazda 6 runs great. But, 4 weeks ago, I stayed in the garage with radio and cell phone charger on, key in Accessory position, while my wife went in the house for 5 - 10 minutes. When she returned, I didn’t have enough battery power to crank the engine. All the gauges went crazy when I tried to start up. I rolled down the driveway for a cheap jump start and drove to the mechanics shop. They put their tester on and said there was nothing wrong with the battery, alternator or starter. We drove off and and didn’t have another problem until last week.

My wife was getting ready for a road trip. She plugged the GPS into the same cigarette lighter socket while she loaded the rest of the car. When she was ready to go, the battery was flat! Turning on the ignition caused all of the gauges to bounce around and the dash lights were dim. Had to use jumper cables to get going. She drove for 2 hours before plugging in the GPS for directions. No problem with the engine running.

The car is still great. We took another trip and waited until we were on the road to plug in the GPS. We are very careful to unplug the GPS and/or Cell Phone (they use totally different chargers) when the engine isn’t running.

What can suck a perfectly good battery down to nothing in 15 minutes through a cigarette lighter outlet without blowing fuses or melting wires or making smoke? I checked carefully for heat or smoke both times.

Shouldn’t happen because of a simple charger or GPS.

There must some current drain when the car is turned to the ‘accessory’ position. Do you have things like auxiliary audio power amps or any other stuff installed in that car?

I agree with RemcoW…Turn the key to “accessory” with nothing plugged into the power socket and see what happens…Most (but not all) lighter sockets stay hot with the key "off’…

You likely have a weak or defective battery. I went thru the same thing. Twice my mechanic checked and said fine despite it basically drained enough not to start after 10 mins sitting with ignition on but engine not running.

Finally HE left ignition on for 10 mins during state inspection and trying to figure out Service Reminder reset and battery died. Then he called and said yeah you need a new battery :slight_smile:

If it just wouldn’t crank at all, I’d suspect the starter motor might be on its last legs. But that wouldn’t explain the dash lights going dim. That sounds more like a battery power issue. But the battery indeed could still be good, and the problem is simply the connections to the battery need to be carefully cleaned and tightened. I’d do that first before assuming the problem is the battery or alternator or something more expensive.

Any mechanic with auto-electric experience can readily determine if your cell phone is drawing excessive current from the battery. It wouldn’t take more than 15 minutes. He’ll just put an amp-meter in series with the battery when the engine is off and the key is in the ACC position. Don’t try this yourself unless you know what you are doing, as you could damage other parts of the electrical system-- like the very expensive engine computer – if not done correctly.

Many chain auto repair places and parts stores-- like Sears – will check your battery for free. If cleaning the terminals doesn’t fix it, that’s probably the next step. If the battery is more than 5 years old, it must be considered suspect.

Just a cell phone will not drain a good battery for days plugged in. It is just power consumption electronics. ! second of cranking the starter is more watts than running your cell phone for a normal day. If the cell phone also uses the lighter socket then that may be the problem. It might have an arc to ground only with the socket adapter plugged in.

It sounds like you have the original battery. This battery is about 5 years old, or late middle age for a battery. I suspect that when it was tested, it wasn’t load tested or tested for capacity. You either have a weak battery or you need to get one with more reserve power.

Generally, at least in my opinion, buy the most powerful battery that will fit in your vehicle when replacing a battery.

I agree with the others that suggested the battery is causing the trouble. I presume it is the original battery since the car was new and it is showing signs of failing. It may fail on you when you least expect it so replacing it should fix the problem and help prevent a possible break down somewhere. The devices you are powering don’t draw much current and shouldn’t be any trouble using them normally. At least for a reasonable period while the engine isn’t running to keep a charge up on the battery. Turning on the Accessory mode can turn on other things inside the car which will draw more current. I assume your model needs to have the accessories turned on in order for the power to get to the socket, which is pretty common now.

Some cars have very small battery’s, pop the hood of a Fit and you will see what I mean. The battery is the size of a lawn tractors battery. Accords now come with battery’s half the size of what will fit in the tray. My point is they have very little reserve capacity, especially on today’s electronic full cars. It’s probably not your accessories doing it, it’s leaving the car with the key on. At this point the computer is on, in some cases the lights are on ( you may have HID and they suck battery power ) the radio amp is powered up, fuel pump, etc. I know Cars with navigation can suck a battery dry quickly.

Are there other sockets to plug those devices into?
If so, try plugging them in there see if it happens again. If not, you might have a problem with that particular outlet.

the battery if it is the orignel could be the problem its at that age

Have the battery and charging system checked. Most parts store will do this for free.
I’ll bet lunch that the battery is weak.

It was stated in the OP that a mechanic’s shop used a tester and said the battery, starter and alternator were fine.