Electrics: Parasitic drain or duff battery.

[CTCNetwork]

Hi,

Not being an eelectrical wizard I needed some pointers as to where I may be getting a drain on the S80 or whether the battery was/is duff.
A it of searching and magic happens...

Originally Posted by cheshired5

If you have a charged battery discharging without explanation, you attach a multimeter in series and measure the standby current drain.
50mA (0.050A) is the general maximum drain you want to see so anything notably higher means that you definitely have a parasitic drain which needs finding.

There are then simple procedures for locating the drain but find out if there is a drain in the first place.

Ref the alternator, you can measure output voltage on the alternator itself, voltage drop on the live and ground side, ac ripple and a diode test.
All straightforward and quick checks with a reasonable spec multimeter and eliminates guesswork.

Originally Posted by CTCNetwork

Hi,

Think I have this issue as well on the S80 and was curious as to how to do this test.

Thanks heavens for the tube..



So now just to find the issue...

Could, of course have been a dodgy battery!

Des. . .

Just need to get some clamps to make this easier.

Des. . .

[CTCNetwork]

Hi,

Swapped the battery for a new one. Went to Europe, and have been back to local drives since return. Not one issue at all... So must have been a dodgy battery. The volvo garage tests on the "dodgy one" show it as fine. Not when I had it!
Charged overnight Friday, used for shopping Saturday 15 miles or so. Car static Sunday. Battery dead on Monday!

Tested as above and once the drain had settled it was showing a 1.01 amp draw on the battery.

Is that to be expected or a bit too high?

Des. . .

[cheshired5]

Originally Posted by CTCNetwork

Tested as above and once the drain had settled it was showing a 1.01 amp draw on the battery.

Is that to be expected or a bit too high?

Too high, more than double what's allowable and could see you with a flat battery after a long weekend of no use.
The drain video on my YouTube channel shows you how to quickly find the cause but also check the alternator charging voltage in case of a failing diode.

[SwissXC90]

Originally Posted by CTCNetwork

Tested as above and once the drain had settled it was showing a 1.01 amp draw on the battery.

Is that to be expected or a bit too high?

Much too high. That's a 12 watt drain, like leaving the interior lamp on all the time.

The only reason the new battery appears "OK" is that it is brand new and has a lot of reserve capacity and can survive a 1 amp drain for a longer time.

Ideally, you want to see parasitic drains under the 0.1A area (that's <100mA)

Around 50mA (0.05A) is pretty normal for many cars. But it varies.

Here's one person's experience:
https://www.optimabatteries.com/en-u...parasitic-draw

BUT you really need to make sure the car is asleep - and that means waiting around 30min before you decide the parasitic drain has reduced to a minimum.

[cheshired5]

Originally Posted by cheshired5

Too high, more than double what's allowable

Apologies, more than 20 times the drain not 2 times.
Getting my decimals mixed up.

[CTCNetwork]

Hi,

I need bigger crocodile clips!

What is the draw of the car alarm, does anyone know?

Des. . .

[cheshired5]

Originally Posted by CTCNetwork

What is the draw of the car alarm, does anyone know?

As shown in my video, if it's working correctly, the alarm drain is minimal, maybe 15mA/0.015A

[Das boot]

I had exactly this problem with my V70 , pulled every fuse in the car one at a timeand still couldn’t drop the current on a multi meter.
Eventually tracked it down to a duff alternator . It was charging just fine , but the diode pack was goosed so as soon as the car stopped it started draining the battery through the alternator .
Easy way to check it is put a freshly charged battery in the car when the engine is cold. Leave it for half an hour then pop the bonnet and put your hand on the alternator . If the alternator is warm the diodes are goosed. The pulley on mine was really hot .
And the alternator body looked a bit scabby and white , it had been doing it for a while , and it gets worse and worse as time goes on .

[CTCNetwork]

Hi,

Originally Posted by cheshired5

Too high, more than [twenty times] what's allowable and could see you with a flat battery after a long weekend of no use.

Strange you say this. I discovered that there was a battery issue when having a week in Sardinia and the car was nearly dead when we returned to the uk. This 2 years ago. That battery is with Volvo and despite tests they can find nothing wrong with it. I could. A weekend of not using the car and it was flat!

So I was expecting issue when we were in Sardinia again for a week. Returned and car started first time.

So in my mind, that WAS a duff battery!

Have some decent croc clips now so will do some tests to find where the issue is.

Des. . .