battery keeps going flat,,

[92mr2paddy]

hahah sweet what setting should it be on im a complete noob with electrics

[Grrrrrrr!]

Your battery is going dead flat in a couple of days so the draw is pretty decent .. so set the meter for the 10A range (you'll need to move the lead to the other hole). Anything that gives you a reading is probably drawing too much.

Other thing you can do is put the meter on the 10A range, and put it between the battery terminal and the clamp and you can see what the total draw is.

[92mr2paddy]

ok have double n tripple checked this sh*t,
jumped car, alternator has 14volts at idle or with revs, tested 2-3-4k rpm always the same, at battery 13.8v (same with revs dont change) then once fans come on drops to 13.2v again,
the bosch (2x) pumps each run around 15amp of draw when running, left it running for over half hour, turned off and it started again so alternator def working.

have now disconnected battery totaly as it sitting its at 12.15volts, will leave it till tomorrow night and check if battery holds its charge, if it doesnt this *must* be issue even though its a f*ckin expensive new battery.

i couldnt find anything else drawing any current when key is out, even disconnected an old NOT working hks turbo timer just to be safe.

[jondee86]

funny enough according to the fuse box its the alternator fuse,,
is it possible that a faulty alternator could also be drawing current
when car is off???

Yes it is. The rectifier section in the alternator has battery voltage
sitting on top of the diodes all the time, regardless of whether the
car is on or off. The diodes act as electrical one-way valves to stop
current flowing from the battery positive to the battery negative.

If one of the diodes goes bad and develops a "leak", current will
flow constantly whenever the engine is off. To check this out you
will need to take the alternator out of circuit. Disconnect the battery
first, then disconnect the heavy wire at the alternator... the one that
runs to the battery positive. Then just to be safe, remove the plug
that has the other wires at the alternator. Wrap the free end of
the heavy wire in a rag or tape, as it will be live when you connect
the battery, and you don't want it to weld itself to something shiney.

Now reconnect your fully charged battery, and check the voltage
after it has sat overnight. DO NOT start or run your engine with
the alternator disconnected.

Cheers... jondee86

[rollaholic]

DO NOT start or run your engine with the alternator disconnected.

why not?

[jondee86]

Fecked if I know Maybe it will do something bad, maybe not.
But since I was giving advice, I thought better not take a chance.
Autoshop101 says... "Never operate an alternator on an open circuit
(battery cables disconnected)." and that sounded like the same
kind of thing as having the alternator disconnected.

Cheers... jondee86

[iOnic]

They can destroy themselves if run with no load.
That and it isn't really a good idea to run the car straight off the battery especially if its losing voltage.

[sergei]

if you disconnect all the plugs on the alternator you should be ok running it disconnected (as there will be no voltage induced).

[jondee86]

That's ^^^ the theory. But I also have read that if the alternator
has some residual magnetism, and you give the engine a decent
rev, it can self-excite (ooh err!!) and start to generate, even if the
external excitation connection is missing.

Kind of off topic anyway, as the point of taking the alternator out
of circuit was just for checking if it is the alternator that is sucking
the battery low. You don't need the engine running for that

Cheers... jondee86

[sergei]

That's ^^^ the theory. But I also have read that if the alternator
has some residual magnetism, and you give the engine a decent
rev, it can self-excite (ooh err!!) and start to generate, even if the
external excitation connection is missing.

Kind of off topic anyway, as the point of taking the alternator out
of circuit was just for checking if it is the alternator that is sucking
the battery low. You don't need the engine running for that

Cheers... jondee86

The alternator is a synchronous generator - it needs substantial sustained current in the rotor coil to generate voltage in the stator coils. If it was asynchronous type (like induction squirrel cage motor) then it could easily self excite from residual magnetism.
Of course it could feedback via regulator into the rotor coil, but I don't think this will happen, as the coil is behind a transistor, and that alone needs 0.5v bias to open. Besides the whole regulator circuit is turned on by IG output, to prevent exactly the scenario where it could self-excite.

Another way it could self excite: is via diode in the regulator that is shorting the rotor coil, this could lead to asynchronous like operation, but I am not sure if the it is possible with half of the wave form not feeding back into stator.

[92mr2paddy]

Meter set to 2000uA, reading 119 so 0.000119 Amps? Thats not the problem. Keep looking.

like grrrrrrrrrrrrr (less *r's? ) said this isnt the cause then only thing else could be battery,

the battery voltage has dropped to around 10v over the w.end now so will get a replacement battery and try it all over.

[matt dunn]

Meter set to 2000uA, reading 119 so 0.000119 Amps? Thats not the problem. Keep looking.

like grrrrrrrrrrrrr (less *r's? ) said this isnt the cause then only thing else could be battery,

the battery voltage has dropped to around 10v over the w.end now so will get a replacement battery and try it all over.

Not really a good indication that the battery is no good.
More an indication that it was not charged enough.

If it was down to 3 volts as you said and you connect it with jumper leads to a car that is running and putting 14.4 volts into it,
you would need to leave it running for a few hours to charge the battery enough for it to hold voltage by itself.

[Lloyd]

It isn't worth testing much until you charge it properly (ie, not with alternator).

[matt dunn]

It isn't worth testing much until you charge it properly (ie, not with alternator).

Correct, and if it is the sort that you cant get the tops on to check the acid it is probably a calcium battery and so will definately need a calcium charger to get it back up if it has been at 3v.

[92mr2paddy]

have bought a new alternator got it cheap from a mate, changed it out, current output etc all still the same.

took car back to shop for them to test battery properly and charge it etc, found the battery is fine and there 'is' something draining battery, they said nothing they have installed link, coils, pumps etc etc has any power with key out.

i now have a kill switch at battery to just turn it off when its sitting at home,, but is there any other things i could check, would a faulty clock cause this somehow or cigarette lighter? my car is pretty stripped so there arent alot of electrics left in there.