Troubleshooting Battery Draining

[Duncan]

Hey All,

My battery has taken to draining itself lately

It isn't driven during the week but does get run on the weekend. The battery is brand new heavy duty century battery, and it shows 13v across the battery terminals when the engine is running (so the alternator is working OK?)

Anyway, how do I hunt down what is making it go flat? I don't believe its natural

[tedy]

I have just replaced the battery in an r33 and was getting 14.5V across the terminals when it was running. Also it could be something the runs even when the car is turned off.

[eXc]

Yeah 13v is kinda low i woulda thought 14v when running, 12 without.

Also, if you want to test the battery, put voltmeter on it...watch it...get mate to crank engine, if it drops below 10v when it cranks time for a new battery.

Start it up, drive to batrery world and ask if they can test the battery and the alternator for you..it's free....

dont forget if u r getting 13v.....when u turn on the lights, a/c, neons? subs etc etc it will drop more, so you need to test it with those things running.

[Duncan]

rofl neons and subs eh? its my race car

Thanks guys

I'm assuming that it is being drained by "something" that draws power when the car is off? it starts fine off a booster pack and the alternator seems OK?

Is there a way to track the drain?

[dangerous_daveo]

How is the computer installed? I was pretty sure you had an aftermarket one? That or say maybe an interior light is left on somehow. Or even just a dash light. I remember on one of our old cars we turned off the interior light, but the door open light still stayed on, so if the car got left for a few days, the battery was dead.

I dont think its something big tho.

[Chris Rogers]

do you have an ammeter?

if so put it inline with the battery and start pulling fuses. when the drain stops you have your problem.

[eXc]

rofl neons and subs eh? its my race car

Hence the *chuckle*

could it be fuel pump direct power (if you did it) did you use a relay? Check it's working correctly.

[Duncan]

Yeah I checked out the obvious power sources today all seems OK. Might be battery after all even tho it is new I guess its not impossible?

Failing that its pulling fuses and checking ampage

thanks everyone

[cowie165]

It has been a while since I did any electronics... How do you go about putting the ammeter in series with the battery?

1. Disconnect -ve

2. Tape? the disconnected terminal to the +ve probe, then jam the -ve probe into the battery?

Is that right? Is there a tidier way to do things? I think one of my reversing lights is draining the system.

Mark

[eXc]

duncan, go to battery world, get battery and alternator checked.

It's quick, easy, free and will count out 2 of the most likley possibilities.

[Sumo]

Thats right, If their is a diode gone in 1 or more phases of your altenator, we have seen drains up to 4 amps. Thats would also explain why the charge rate is very low. Easy way to do it as the boys have said, put a ammeter inline and pull the leads off the back of the alt.

Cheers

Matt

[GTaaargh]

A guy at work had his battery go flat if he left it unused for a week.

Turns out the company who put in his alarm didn't do the relay right.

[wishaw]

Yeah I checked out the obvious power sources today all seems OK.  Might be battery after all even tho it is new I guess its not impossible?

The only reason i doubt it is the battery is that the voltage while the car is running is only 13v. That should be up around 14.5v if your battery is working ornot.

[Sumo]

wishaw, I dont fully agree with that.

If you have a really flat battery, the altenator will not be able to produce 14.5Volts at the battery terminals, you will find as the battery charge level goes up, the voltage will eventually rise - but this takes quite a while. Its not uncommon to see an altenator putting in 12.8 volts and it may rise to 13.2 volts and stay their for a while.

You will only get maximum voltage being produced when everything is in top working condition. The battery is a crucial element that makes up the charging system. Its funny you know, I get old blokes coming in saying that once a car is running you can pull a battery lead off to make sure the "generator" is working..... Not these days Once you loose your field power the alt will stop charging. Once they work figure out Perpetual Motion, you will only need a battery to start it.

Cheers

Sumo

[Duncan]

Thanks to everyone that posted up here....

I checked the voltage again while it was running and it was 12.5v....so checked the alternator again and the farking thing was not connected properly

the apprentice who helped put the engine back in (yes, me) didn't connect the earth for the alternator. pretty obvious mistake and I'm kicking myself for missing it twice when i checked it.

Sumo....re your post, I have run the car without a battery in, just relying on the alternator to run it, it ran OK? Or did I missunderstand?

[Sumo]

Duncan, heh, well the only thing that might make it keep on charging is the residual magnetism in the rotor. Either way, its not a good thing

Generally altenators dont have an earth on them, They usually earth through the common earth to the engine block. They should have 2 or 3 wires and a main lead going to them.

Cheers

Sumo

[Sumo]

Just thinking about disconnecting a battery whilst its running, In the odd chance that the altenator was still able to produce voltage - The sensing wire would sense 0 volts at the battery, therefore you could have a voltage spike upwards of 17 odd volts, not good.