Battery drain woes...

[Hertsdriver]

Hi all,

My car (997.1 3.6) is being used daily (long drives of over an hour to and from work), and last week I had an unexpected new issue where the battery one morning was completely flat.

I thought perhaps it was just the very cold, early morning starts showing up a deficiency in the old battery that came with the car (a relatively small, lower amp Lion brand battery that was probably fine for the previous owners occasional use as a second car), so I went to Halfrauds and bought a larger Yuasa 85ah battery, fitted it and thought nothing more. However the next morning the battery was completely flat again... so I clearly have a drain somewhere.....

I don't know if its connected but I also had last week a random fault code showing on the dash saying that the rear passenger side brake light was inoperative, it would clear itself after 10 minutes or so, only to reappear the next day which si odd (have since replaced both rear brake light bulbs, although neither had blown filaments).

So anyway, with the new battery trickle charged overnight, I got the multi meter out yesterday to see if the alternator was working or not. Got a reading of 12.53 with the battery connected but nothing being used (frunk catch closed with a screwdriver as per De morts advice to stop the light from coming on) 13.29 with the engine running, and 12.98 with all accessories on (lights, hazards, fogs, heater, rear demister, radio. So I believe the alternator is doing what it should?

Shut the car off, pulled the fuse for the aftermarket radio (just in case it was this that was the issue) and the battery measured 12.04. and hour later it measured 11.88, and an hour later had dropped to 11.74. by 9pm it was down to 8.82.... :?: seems like quite a drastic drop, wonder if there are any likely culprits to check that are known to fail before I have to start the process of pulling fuses and measuring...

Thanks :thumb:

 

[jl-c]

I have one of these, not cheap but saves loads of time with issues like the one you are suffering.

https://www.hubitools.com/en/catalog/the-amp-hound~a23e7fc9-dc47-cbe6-fc00-39eabe1cecea

For some reason they seem hard to source in the UK. Got mine used off ebay. Great tool for finding parasitic drains.

 

[badbadtz]

I have one of these, not cheap but saves loads of time with issues like the one you are suffering.

https://www.hubitools.com/en/catalog/the-amp-hound~a23e7fc9-dc47-cbe6-fc00-39eabe1cecea

For some reason they seem hard to source in the UK. Got mine used off ebay. Great tool for finding parasitic drains.

Wow that's a very expensive way to measure voltage drop across a fuse ...you can do the same using a £10 multi-meter from Amazon.

 

[jl-c]

I have one of these, not cheap but saves loads of time with issues like the one you are suffering.

https://www.hubitools.com/en/catalog/the-amp-hound~a23e7fc9-dc47-cbe6-fc00-39eabe1cecea

For some reason they seem hard to source in the UK. Got mine used off ebay. Great tool for finding parasitic drains.

Wow that's a very expensive way to measure voltage drop across a fuse ...you can do the same using a £10 multi-meter from Amazon.

Actually, no you can't, but hey if that's what you believe, feel free. :hand:
You would need a very precise microvolt meter as a fuse is essentially a short otherwise it wouldn't work :floor:

 

[deMort]

You Have more than one issue im afraid ..

Alternator being one of them .. below 13 volts on a full load check is too low .. battery is not getting enough charge .

That's not flattening your battery over night though .. you have a voltage drain and a pretty big one ..

I would check your seats .. nothing pushing against a seat switch is there ?

That's an intermittent 6 amp discharge if so ... thinking umbrella down the side of the seat here ..

Fuse pulling and measuring current draw is the next option .


Amp hound is an awesome bit of kit .. it measures current draw over a fuse and so saves having to pull fuses and see what the drop is on the amp meter .. bearing in mind you can't pull alarm fuses ... so ... it's just .. Excellent !!

To be fair i use it on every job like this .. as an owner you would only use it once i would expect ... expensive but for people like me it's invaluable ..

I could go on about it and the benefits but that's not what this post is about .. sigh .

 

[brownspeed]

its not beeping when you lock it is it? Mine was when i had this problem and couldn't figure it out fot ages. It turned out to be a button lodged behind the glovebox which was keeping the glovebox courtesy light on permanently.
just a thought.....

 

[timbo1811]

.............'a fuse is essentially a short .............'

can someone explain this to me?

 

[jl-c]

Yes, a fuse is a short. As in a calibrated piece of wire that will burn out as a predetermined current flows through it. It is not a short as in short to earth that will just go bang :sad:

 

[badbadtz]

I have one of these, not cheap but saves loads of time with issues like the one you are suffering.

https://www.hubitools.com/en/catalog/the-amp-hound~a23e7fc9-dc47-cbe6-fc00-39eabe1cecea

For some reason they seem hard to source in the UK. Got mine used off ebay. Great tool for finding parasitic drains.

Wow that's a very expensive way to measure voltage drop across a fuse ...you can do the same using a £10 multi-meter from Amazon.

Actually, no you can't, but hey if that's what you believe, feel free. :hand:
You would need a very precise microvolt meter as a fuse is essentially a short otherwise it wouldn't work :floor:

To find a parasitic drain you'll be fine measuring in the millivolt range and not microvolt range. And thanks to cheap Chinese electronics you can pick up a multimeter sub £20 that'll do low mV in the low 10's. Spend a bit more ~£50 and you'll get to single figure mV.

Or you could just remove the fuse and measure the current in series with your cheapo multimeter :roll:

 

[badbadtz]

.............'a fuse is essentially a short .............'

can someone explain this to me?

Don't worry I've never heard a fuse being described as a short before. A fuse is simply a protective safety device which is designed to melt when an excess current flows through it

 

[jl-c]

OK, final reply. If you could do it your way why do OPC and independants buy a Amphound? You obviously believe it is all snake oil. You are entitled to your own opinion of course but see deMorts reply. Also about removing alarm fuses. I'll just send my Electronics Degree back and give up electronics as you obviously know far more than we do.Reply if you so wish but I will not bother replying.

 

[timbo1811]

.............'a fuse is essentially a short .............'

can someone explain this to me?

Don't worry I've never heard a fuse being described as a short before. A fuse is simply a protective safety device which is designed to melt when an excess current flows through it

well thats what I thought! but was concerned I'd missed something

 

[badbadtz]

OK, final reply. If you could do it your way why do OPC and independants buy a Amphound? You obviously believe it is all snake oil. You are entitled to your own opinion of course but see deMorts reply. Also about removing alarm fuses. I'll just send my Electronics Degree back and give up electronics as you obviously know far more than we do.Reply if you so wish but I will not bother replying.

I think you should re-read my original comment where you will find my only statement was that it was very expensive for what is essentially just measuring voltage drop across a fuse. At no point did I imply it was snake oil, question the usefulness of said tool or challenge your suggestion and knowledge. It was in fact you who challenged me with questionable integrity (microvolts vs millivolts).

And not that it makes an ounce of difference but I also have an engineering degree but that does automatically mean I know everything and I'm always willing to learn something new.

Anyways, I apologise if you felt this was somehow personal when it was not. ...and apologises to the original poster for hijacking this thread

 

[Cannop]

OK, final reply. If you could do it your way why do OPC and independants buy a Amphound? You obviously believe it is all snake oil. You are entitled to your own opinion of course but see deMorts reply. Also about removing alarm fuses. I'll just send my Electronics Degree back and give up electronics as you obviously know far more than we do.Reply if you so wish but I will not bother replying.

Why so confrontational? There's a lot of incorrect assumptions in your flounce!

 

[Cannop]

Double post - ooops!