Mazda 6 1.8 petrol draining battery every few days

fonecrusher1

Hi folks.

My Mazda 6 petrol has been suffering with a flat battery every few days. This started a few weeks ago so I presumed the battery was done. I bought a new one 2 weeks ago and much to my frustration its happening again and this time I know for sure its not the battery.

Any ideas on what is causing this? I can't see any interior lights on that might be draining the battery. What else can do this to the battery? I know if you leave a car undriven for 2 weeks + the battery is going to die but this is ridiculous. I'm having to use the battery charger every time I don't use the car for 2 or 3 days. One thing I should mention is the radio doesn't work. Could that be contributing to the problem?

Thanks

F

Doublebusy

Alternator possibly

fonecrusher1

Doublebusy wrote: »

Alternator possibly

Hi.

I was thinking that but I do very short journeys in the car at the minute. Alternator only tops up battery when its on the move? Two days before the last time the battery went flat before I left the car I made sure the car could start again after I drove it. To see if the battery was holding its charge and it started first time. If it was the alternator it would have had some issue cranking, something would have indicated the battery was not being charged while on the move.

Not ruling out the alternator though.

Doublebusy

Most garages will put a meter on an alternator to see what reading it gives - free of charge. To eliminate that as the problem

fonecrusher1

Doublebusy wrote: »

Most garages will put a meter on an alternator to see what reading it gives - free of charge. To eliminate that as the problem

I have a multimeter. Am I right in thinking if I get a reading of 12v on the battery and if after I start the car and turn on the lights and this drops significantly below 12v then the alternator is not doing its job? It should remain at 12v or above?

Cee-Jay-Cee

The battery should be around 12.5 - 12.8v when the engine is switched off.

It should rise to 13v and above when charging/engine running.

I know it might be obvious but is the boot light on although in my Mazda 6 the boot light goes off when the boot lid is closed but there could be a fault in the circuit meaning its staying on when the lid closed. If its a hatchback drop one of the seats and check.

If there is nothing else obvious you can do a check on the battery to see if there is parasitic drain on the battery when the engine is off. Its a simple test to do if you have a multimeter.

Watch this to see how to do it >>> https://www.youtube.com/watch?v=XH2wdHBZ6eE

TherapyBoy

fonecrusher1 wrote: »

Hi.

I was thinking that but I do very short journeys in the car at the minute. Alternator only tops up battery when its on the move? Two days before the last time the battery went flat before I left the car I made sure the car could start again after I drove it, to see if the battery was holding its charge and it started first time. If it was the alternator it would have had some issue cranking, something would have indicated the battery was not being charged while on the move.

Not ruling out the alternator though.

Stop doing both of these.

The alternator will charge up your battery as you drive but the car needs to be driven. Driving very short distances might not be giving your battery a chance to recharge.

Starting your car just to see if it will start & immediately turning it off again does nothing but drains power from your battery.

These actions alone might not have anything to do with your current battery problems, you might have a parasitic drain elsewhere or your boot-light is staying on or your alternator isn’t working properly etc but using your car in this way isn’t good for battery health.
Think of your battery as a two litre water bottle. Whenever you start your car it takes a half litre out of the bottle to do so, you can fill the bottle back up but it takes 15 minutes of holding it out the window for the rain to refill it. Starting your car without driving it afterwards or driving very short distances doesn’t allow your battery to ‘refill’.

fonecrusher1

TherapyBoy wrote: »

Stop doing both of these.

The alternator will charge up your battery as you drive but the car needs to be driven. Driving very short distances might not be giving your battery a chance to recharge.

Starting your car just to see if it will start & immediately turning it off again does nothing but drains power from your battery.

These actions alone might not have anything to do with your current battery problems, you might have a parasitic drain elsewhere or your boot-light is staying on or your alternator isn’t working properly etc but using your car in this way isn’t good for battery health.
Think of your battery as a two litre water bottle. Whenever you start your car it takes a half litre out of the bottle to do so, you can fill the bottle back up but it takes 15 minutes of holding it out the window for the rain to refill it. Starting your car without driving it afterwards or driving very short distances doesn’t allow your battery to ‘refill’.

Appreciate the input but this is the way I have driven the car for a long time. Quite a few years and only now am I seeing this problem. I mean very short journeys. Its not related to how i'm driving the car 100%. If that was the case this problem would have revealed itself years ago. A decent battery in a stationary car should last about 2 weeks before it goes flat. No less that a week.

I do agree its most likely a parasitic drain on the battery though which i'm still investigating. New multimeter ordered because the one i have is shot.

Curious_Case

fonecrusher1 wrote: »

Hi folks.

My Mazda 6 petrol has been suffering with a flat battery every few days. This started a few weeks ago so I presumed the battery was done. I bought a new one 2 weeks ago and much to my frustration its happening again and this time I know for sure its not the battery.

Any ideas on what is causing this? I can't see any interior lights on that might be draining the battery. What else can do this to the battery? I know if you leave a car undriven for 2 weeks + the battery is going to die but this is ridiculous. I'm having to use the battery charger every time I don't use the car for 2 or 3 days. One thing I should mention is the radio doesn't work. Could that be contributing to the problem?

Thanks

F

Definitely, the radio is worth investigating - it isn't working anyway so take out it's fuse to see if things improve.

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