Battery problem

[Knight Rider S4]

Right my pet hate is a electrics so hopefully this will be clean cut i hope :?


Battery is discharging over a period of 2 days and something is taking the charge out

Have bought new battery, calcuim one so more than enough for the car and winter so that is ruled out

So what could be the main culprit?
Diode in alternator?
Earth strap is fine
Still have to do the fuse test with multimeter but hoped someone will tell me a common problem before i go down that route


The car is an Avant so battery is in the boot so is there anything i should be checking with regard to wiring tracing back to engine?

Cheers

Steve

[jameswkr]

Could be something simple like the boot light remaing on (BTDT). Have you checked the rate of discharge with everything switched off?

[alanhj]

is your radio/cd changer on the ignition?? i had a similar problem turned out to be the cd multi changer. rewired it to the ignition and all was fine!

[sjw185]

disconnect 2 main positives off the battery and split them, check for current drain with ammeter one at a time to determine whether its draining from the alternator or the fuses box. mine was the altenator

[turnip]

Previously left my RS2 for 2 weeks at airport fine on return . Car sat in drive for 4 days with radio faceplate on ( not switched on but still displays time ) = flat battery

[Error404]

disconnect 2 main positives off the battery and split them, check for current drain with ammeter one at a time to determine whether its draining from the alternator or the fuses box. mine was the altenator

I have a similar problem - supect the alternator, but would be handy to check which direction the look in. I'll be honest my electrical skills and knowledge are minimal!!

Can you give a bit more of a detailed 'how to' for testing these two main positives?
Do you place the multimeter across a disconnected positive and the battery nagative?
What is a normal reading?

[Error404]

Bump to an old thread.

How do I test for currrent drain? Got a battery going flat pretty quick, want to see whats drainging it - whats the proceedure?

Also my alternator is behaving funny since the cars been stood for 10 months - If I start the engine the volt gauge only shows about 11 volts and car runs rough - seems the alternator is not charging properly - then after a few minutes the voltage slow creeps up to 13.5v or thereabouts and all is well.
Belt is tight, and alternator is only about a year old, but it was a GSF special - anyone got any clue what going on?

[Henkjan]

take the + off the battery, insert a decent multimeter that displays aperes and take out the fuses one at a time...
I found that boot light was on, radio&CD changer take a fair amount even when off... (I'va had my share of dead batteries)

[Error404]

sorry, i am very dumb when it comes to electrics ... insert a amp meter where?

What do i set my multimeter too and where do I put the two prongs?

cheers

[mcandmar]

Set your multimeter to amps, then use it to bridge between the positive cable and the positive on the battery. That way you can measure the amp draw from the battery.

I have the same problem with our S4, but the problem is the amp draw is more than my multimeter can handle so it cuts out. Really annoys me as i have to start the car every 3-4days to keep the battery alive as i cannot figure out whats causing it.

[xgordyx]

sorry, i am very dumb when it comes to electrics ... insert a amp meter where?

What do i set my multimeter too and where do I put the two prongs?

cheers

As Henkjan said remove the + lead from your battery. Connect one of the probes (+ or - it don't matter) to the + lead and connect the other probe to the + terminal of the battery.
Set your meter to amps and you will see how much current is being drained from your battery. Again as Henkjan says start to pull your fuses one at a time and see if the amps drop off on the multi meter.
Don't switch your ignition on as you can run the risk of damaging your multi meter, at very least if your meter is fused you'll blow the fuse

[xgordyx]

Set your multimeter to amps, then use it to bridge between the positive cable and the positive on the battery. That way you can measure the amp draw from the battery.

I have the same problem with our S4, but the problem is the amp draw is more than my multimeter can handle so it cuts out. Really annoys me as i have to start the car every 3-4days to keep the battery alive as i cannot figure out whats causing it.

When you say your meter cuts out. Does it pop the fuse or just goes off the scale and not give a reading?
What you could do (i know it would be a pita) pull all yor fuses then check to see if your meter will read without "cutting out", if so start to replace the fuses untill your meter "cuts out". That way you'll have a rough idea of the problem.

[mcandmar]

I hadnt thought of doing it that way round, obvious now that you say it

Cheers,

Mark.

[xgordyx]

I hadnt thought of doing it that way round, obvious now that you say it

Cheers,

Mark.

The reason i said to pull all the fuses as i didn't know if it was blowing fuses. I know my fluke at work blows fuses if overloaded (my old fluke threw it lt's legs in the air when it got mega overloaded, shorted across the battery don't tell my boss ) and my blue point one at home blows a fuse if overloaded.
But if your not blowing fuses you can be too far out of range and pulling fuses like you say one at a time to get a reading is certainly a better way to go.

[Nuvo]

This is a useful thing to carry in your tool box.

It would be ideal for your needs.