HELP! Flat battery woes!

[rdholmes]

I have an 04 1.8T last of the mark 1's and the cig lighter is always live - keys or not.

[M47Rman]

Oh dear more bad news on the battery front
I went to use the car at lunchtime today. Got in OK, all seemed well until I tried to start it and nothing, just a click. There was still enough juice to re-lock the car so I have done, and just left it!
I have not checked the voltage so have no idea what level it is at now, but after being charged for two days, and only started once, then left standing for three days, I was not expecting problems.
So I will be looking for a new battery later, and I am hoping that is the only problem.
Just in case, what are the most common causes of battery drain on our cars? I do have sat nav, but it has not been in since the battery was refitted. The stuff in the boot all seems to go to sleep (stop buzzing) after a couple of minutes of being locked, and the lights are not on! Anyone got any suggestions?
Andy

[Keith]

Oh dear!

Perhaps you better stick a meter on it and see what is being drawn once the car has been locked then give it say 30 minutes to go to sleep

iirc DeeCee posted his findings 80MA I think once fully asleep

[M47Rman]

Originally Posted by Keith

Oh dear!

Perhaps you better stick a meter on it and see what is being drawn once the car has been locked then give it say 30 minutes to go to sleep

iirc DeeCee posted his findings 80MA I think once fully asleep

Hi Keith
thanks for the info
being a TOTAL electrical klutz, how (and where) do I go about measuring that?
I have a multimeter, but all it is ever used for is measuring voltage across a battery, and the occassional resistance! College electrics are (mercifully) a very distant memory.
Complete IDIOTS guide please!!
Andy

[Keith]

Well er um
To measure current you need to put a meter set to measure DC current in series with the battery or ideally one of the fuses how you go about this primarily depends on the meter you have

NB When measuring volts you are measuring in parallel across the battery!

Most digital meters read in a positive and negative direction so it does not really even matter if you get the wires round the wrong way either!

Most cheap DIY type meters have a 10A (amp) current range and then so on down the scale some have multiple ranges one 10A protected via a fuse and the rest up to 2A protected via another fuse chances are the 10A range will not give accurate enough results as you are looking for two or three places of decimal here to read > 100MA and the 2A range fuse will blow with the ignition on!

In an ideal world you would have a high quality fully auto ranging meter capable of handling any current at any polarity but they are expensive!

There are various ways to do this but as we are dealing with a big battery and a lot of current I do the following which can be a bit tricky at first to get the hang of if you are not that good at juggling.

Undo the red lead to the battery but don't disconnect it, connect one lead of the meter to that red lead the other to the battery terminal, effectively then when you remove the red lead current continues to flow via the meter without any interruption to the cars electrics

It helps to clamp or tape down the bonnet switch whilst doing this so you can superlock the car

The idea being to pull the battery lead off once you have locked the car and note the current drawn then wait and note after 15-30 minutes or so

If the meter goes out of range simply reconnect the battery lead adjust the meter range and disconnect unless the meters fuse blows the car won't even notice!

Leaving your sat nav disconnected whilst doing this is a good idea to avoid any chance of damaging it.

[Keith]

Thought I better track down DeeCees' thread (I wonder where he has gone)

http://www.the75andztclub.co.uk/foru...ead.php?t=1022

Looks like you will need a high current range to start with

[M47Rman]

Originally Posted by Keith

Well er um
To measure current you need to put a meter set to measure DC current in series with the battery or ideally one of the fuses how you go about this primarily depends on the meter you have

NB When measuring volts you are measuring in parallel across the battery!

Most digital meters read in a positive and negative direction so it does not really even matter if you get the wires round the wrong way either!

Most cheap DIY type meters have a 10A (amp) current range and then so on down the scale some have multiple ranges one 10A protected via a fuse and the rest up to 2A protected via another fuse chances are the 10A range will not give accurate enough results as you are looking for two or three places of decimal here to read > 100MA and the 2A range fuse will blow with the ignition on!

In an ideal world you would have a high quality fully auto ranging meter capable of handling any current at any polarity but they are expensive!

There are various ways to do this but as we are dealing with a big battery and a lot of current I do the following which can be a bit tricky at first to get the hang of if you are not that good at juggling.

Undo the red lead to the battery but don't disconnect it, connect one lead of the meter to that red lead the other to the battery terminal, effectively then when you remove the red lead current continues to flow via the meter without any interruption to the cars electrics

It helps to clamp or tape down the bonnet switch whilst doing this so you can superlock the car

The idea being to pull the battery lead off once you have locked the car and note the current drawn then wait and note after 15-30 minutes or so

If the meter goes out of range simply reconnect the battery lead adjust the meter range and disconnect unless the meters fuse blows the car won't even notice!

Leaving your sat nav disconnected whilst doing this is a good idea to avoid any chance of damaging it.

Thanks Keith
EXTREMELY comprehensive instructions as always!
Actually quite chuffed, as I had remembered the series bit (don't laugh) and I had already thought of taping down the bonnet switch.
As for my multi meter - very cheap black spur item, with simple needle type probes, so not too sure how I am going to connect them as yet. Hopefully have a go later this evening.
Andy