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E30 hobby car 01-12-2013 10:51 AM

battery drain
 
1 Attachment(s)
my battery is completely dead, and will drain quickly.

Besides the fact that its old and needs to be replaced. I think there is an electrical problem.

when following advice, using my volt meter on my fuse panel, water the meter and remove fuses until the drain goes away... ?
is that the suggested route of trouble shooting?

I couldn't seem to notice any change.

here is a picture of what i was doing. maybe i used the leads on the wrong spot?


and when i measure positive to body, i get the full battery voltage.

downhiller 01-12-2013 01:43 PM

your doing it wrong. what you need to do is remove the positive cable from the battery. attach lead to cable with alligator clip then the other lead to the positive terminal of the battery. then from there youll have your parasitic draw. and of course, now you remove the fuses one at a time and watch the change then from there you can find the location of the circuit that youre having problems with

Billwill 01-12-2013 11:24 PM

Quote:

Originally Posted by downhiller (Post 7308690)
your doing it wrong. what you need to do is remove the positive cable from the battery. attach lead to cable with alligator clip then the other lead to the positive terminal of the battery. then from there youll have your parasitic draw. and of course, now you remove the fuses one at a time and watch the change then from there you can find the location of the circuit that youre having problems with


This is correct but the OP needs to know that the Multi meter must be set to read DC AMPS and you have to move the red lead of the meter to a seperate plug point marked DC AMPS.

Of course if you try start the engine you will blow the fuse in the meter.:cry:

BMWFatherFigure 01-13-2013 03:23 AM

+1, but I would hope the OP knows the difference between Volts and Amps anyway.

downhiller 01-13-2013 12:15 PM

Quote:

Originally Posted by Billwill (Post 7309610)
This is correct but the OP needs to know that the Multi meter must be set to read DC AMPS and you have to move the red lead of the meter to a seperate plug point marked DC AMPS.

Of course if you try start the engine you will blow the fuse in the meter.:cry:

you sure? its hard to tell with the gopro fish eye pic. i always do it from the battery, its easier but of course more walking on these cars

E30 hobby car 01-13-2013 01:26 PM

2 Attachment(s)
Camera upgrade,

I did make the mistake of only testing in volts earlier, and when i switched to amps, I noticed 2 fuses casing a draw.

however, there is still a small draw.

test idnicated a draw of 1.2amps.
one fuse dropped it to .5 amps. the final fuse dropped it to .3 amps....
thats as far down as the meter went. So, there is still a draw some where.

BMWFatherFigure 01-13-2013 09:58 PM

1.2A is a HUGE drain. Alarms, clocks and memories etc run 0.03A total, typically.

Billwill 01-14-2013 12:08 AM

Disconnect the alternator...a fused out diode can have the power flowing back down to ground.
See if that helps limit the draining current.

I still cannot work out from your picture how you are measuring current in series with the battery...best to totally remove the large battery clamp from the battery...connect the red lead from your meter to this clamp and the black meter lead to the red terminal on the battery. This way you will definitely get all current flow, including the flow through the alternator.

I see from your first picture that the right-most plug position on your meter will let you measure milli-amps provided you turn the rotary switch to the correct position...the plug position you are using is for up to 10 amps probably.

BMWFatherFigure 01-14-2013 03:27 AM

Start with large amp reading and work your way down :thumbup:

E30 hobby car 01-15-2013 04:40 PM

how would an alternator consume energy while its just sitting there?

I will have to try it.

In terms of how i was measuring it, look at where my leads are. They are touching the red and green main cables, from what i think are at the fuse panel... i dont know.. look at the picture.

It seems as if you are all suggesting i am doing it wrong. so, I will try the battery approach.

downhiller 01-15-2013 04:43 PM

in order to do an accurate amp reading for dc volt the meter needs to be in series with the circuit, not parallel.

E30 hobby car 01-15-2013 06:33 PM

1 Attachment(s)
right! that approach makes much more sense. I had a weird reading, I would read the amp draw, it would climb to .68amps, then trickle down to .03. and it would stay there. I would remove the meter, wait 20 seconds, and it would do it all over again.

either way, i have isolated the trouble makers. With almost ninga like skills. I only tested 3 other fuses besides the bad ones.. i know...awesome.



anyway,
fuse 21, amp draw went from .03 to .01

fuse 27 went from .01 to .00...

fuse 21: glovebox light
flastlight?
ignition key/seat belt warning
interior lights
radio memory
trunk lights
radio memory
active check control
service interval indicator
obc?
fuel delivery
tachometer/fuel economy gauge ..... (mine swings back and forth)
digital clock
multi function clock.


Fuse 27-30 (fuse 30 was fine)
interior lights
central locking
obc?
radio amp

E30 hobby car 01-16-2013 03:27 PM

so... now what?

downhiller 01-16-2013 03:57 PM

.03 amps sounds right for a normal reading/non excessive amp draw

nedfunnell 01-16-2013 06:18 PM

Yeah- if 0.03A is all you're drawing with all the fuses in place, then I don't think you need to worry about it. Was this test performed at the battery per others recommendations?

E30 hobby car 01-16-2013 06:21 PM

well, what about the spiking of .68 amps? and yes, these measurements were taken in series with the battery.

and when i took the 2 fuses out there was 0 draw.

nedfunnell 01-16-2013 06:22 PM

Spiking to 0.68A is a problem. When does it do that?

E30 hobby car 01-16-2013 06:24 PM

when i take the amp meter off the leads, 20 seconds later, i test it, it spikes to .68 and slowly goes back down to .03

Sort of like, it builds up and the amp meter dissipates the build up

nedfunnell 01-16-2013 06:27 PM

That is a bit odd... but what I would assume is that the OBC, radio, etc are very briefly 'waking up' when they first get power (when you attach your meter) then they quickly go into their sleep (low power) state. If it stays at 0.03 as long as you keep your meter connected, I would say you are good to go.

I tried to nurse the battery along in my beater last year. It wasn't worth it. (Speaking as one of the cheapest people I know) I replaced it and forgot all the trouble I had trying to eke out the last bit of life from a dying battery. I'd say replace it and see if you have the draining problem with the new one.

E30 hobby car 01-16-2013 06:31 PM

i guess thats the only thing left to do.

i want a really light battery. my old one is such a POS. has to weigh close to 40 pounds or more

nedfunnell 01-16-2013 06:33 PM

http://www.motoiq.com/magazine_artic...-plumbing.aspx

There's a starting point for a light battery. Probably would need a handful to start an M20, though...

Nick323 01-17-2013 12:49 AM

Understanding current, Voltage & electron flow
 
I have noticed that Automotive Electronics and electrics puzzle most people to no end :eeps:
The more modern a car is, the more you will have to understand it :)
To refer electrical/electronic issues to a professional is an option, but then you might as well have everything done by professionals :dunno:

For instance to say that the initial high current draw is caused by
Quote:

that the OBC, radio, etc are very briefly 'waking up' when they first get power
is correct because the Capacitors in these units have to recharge, but it also shows that you do not really understand the issue.
Please ! I do not want to step on anyones toes or sound like a wise ass, but basic electronic knowledge is something you can read up on & teach yourself.

Billwill 01-17-2013 01:14 AM

A reading of 0.03 Amps is OK.

You get a "surging" of a current reading from the capacitance that you find in any large electrical circuit such as the E30 has....the radio has noise suppression capacitors inside it, same for ECU, cluster etc.

When you disconnect your battery to put your meter in series with it, the various capacitors discharge themselves back to ground.
When you now put your meter in series with the battery....all the capacitors "charge" themselves up....initially at a high current which then tapers off to a low current. This is standard capacitor behaviour....if you have a large capacitor handy....try connect your Ohm-meter over it. The internal meter battery will charge up the capacitor until it is fully charged at which stage it will show virtually open circuit on the Ohm-meter.

If there is a fused diode in the alternator it will allow current to flow back to ground. The diodes act as one-way valves normally so that positive current can flow into the battery from the alternator to charge the battery up.
Disconnecting the alternator temporarily to check for current drain will expose a fused diode but with a drain of only 0.03 Amps (30 milli amps) there is no problem with draining in this case.

A common problem for draining current is if there is no light bulb fitted in the glove box socket. The socket acts as the switch as well and having no bulb fitted at all...even a blown one...can cause a short to ground but this tends to be a rather large current drain which is not the case here.

hornhospital 01-17-2013 08:45 AM

Essentially the same response from Nick and Bill, 25 minutes apart. They are right. :thumbup:

downhiller 01-17-2013 02:32 PM

Quote:

Originally Posted by E30 hobby car (Post 7318958)
i guess thats the only thing left to do.

i want a really light battery. my old one is such a POS. has to weigh close to 40 pounds or more

optima will be about the lightest but also most expensive. the lipo battery wont last in these cars. they only have about a 200cca rating cause they are designed for motorcycles, atvs and smaller motors. we need about 600cca in the m20


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