battery drain.. but no drain? doing my head in

cvega · 2 Jun 2018

So lately I've replaced my alternator voltage regulator. Battery seems to drop really low after 3-4 days. Replaced the battery with Bosch S5 74Ah 700cca.
While driving, the car is showing above 14V. So I assume charging is OK.

I've gotten around to measuring the current drawn and I need some guidance.

This is the way i've connected it;
red (10A on the meter) towards negative on chassis
COM to battery negative

After I lock the car, it's displaying 30-ish for a minute, then drops to 11.5-12 (I'm assuming miliamps - i'm using the meter in 200mA mode):

After additional 10 minutes, it drops to 3.3-3.7:

Even 3 hours later, seems to be the same:

So..what is killing the battery???

Pickse · 3 Jun 2018

I had very similar symptoms on my 996T.
Battery wouldn't last a week although charging was close to 14V.
But sometimes after start it would refuse to produce 14V then after a few seconds would ramp up to the expected charging voltage.

Turned out the serpentine belt was routed incorrectly.
Not enough contact area with the alternator pulley so slipping I guess :?:

andy1985 · 3 Jun 2018

Your pics aren't working for me and I don't know if i'm reading wrong but it sounds like you are trying to measure current the same way as voltage.

To measure current you need to break the electrical circuit and put the meter inline, eg remove the negative battery terminal, connect one lead to that and then connect the other lead to the battery terminl to complete the circuit again.

DON'T try to start the car like this though.

open the door, ignition on,
trick the latch into thinking the door is closed, igntion off and lock the car up and disable the alarm sensors.
Wait for the car to go to sleep and then check the current draw.
If it is high then begin pulling and replacing fuses 1 by 1 to see which circuit is causing the issue.

deMort · 3 Jun 2018

:agree:

Thats how to do it but the problem is if you just pull off the neg lead the alarm will trip ..

you need to rig up a wire to the battery terminal and the lead so that you can remove it but its still connected .

You can then connect the amp meter leads and remove this wire.

All current will flow through the meter at this point and it will display what it is.

I have a 20 amp meter so i just connect it up with ign on and lock the car .. on a 10 amp meter thats a bit close to the max limit so you might blow the meters fuse if you do it my way .

Set the meter to the 10 amp setting , wait 1 hour to get a true reading .. you want a display of 0.03 ... 30 milliamps .

cvega · 3 Jun 2018

Sorry maybe I didn't describe correctly. The meter is inline on the negative side of battery. I put the key into ignition, disconnect it, reconnect with meter online and lock the car.

deMort · 3 Jun 2018

In which case you dont have a discharge .

I would watch the meter for a few mins to make sure its not a pulsed discharge .. trackers do this .

Next step .. car running on idle , all electrical loads on then measure the voltage at the battery .. you need about 13.2 .. if below 13 then the alternator or a lead is faulty .

cubasteve · 3 Jun 2018

Battery problems

:bandit: Try a Porsche trickle charger , plugs into the cigarette lighter also the tracker drains battery and after 3 to 4 days the car goes into sleep mode so check it's not just that , Good Luck . Cuba :bandit: :bandit: :bandit:

911munKy · 4 Jun 2018

^
That looks like a rebadged CTEC charger.
I bet it's a lot cheaper without the Porsche logo.

They are very good trickle chargers though.

cubasteve · 4 Jun 2018

Battery problems

:bandit: Yes it is a rebadged CTEC charger , make sure you buy the one with cigarette lighter plug in . Cuba :bandit: :bandit: :bandit:

cvega · 4 Jun 2018

Thanks chaps, I know all about CTEK chargers but the car should be able to maintain a battery charge for a week without help. For a 3-4 weeks, sure, I'll plug it in, but not every week.

As for the test, I've done a run in the evening, the car was driven the same morning, about 20 miles.
The meter initially shows 12.3V, cranking about 10.8/11 , then sits at about 13.5 for a while (loud whirring sound from the engine bay), goes up to over 14. With load drops to about 13.8 or so (Radio, fans, lights on)
I've recorded this on my phone. Sorry about the sound quality. https://youtu.be/ose8UpdnP94

Stoo.c · 4 Jun 2018

Did you say that with the engine running, you're getting above 14V showing? That seems a little high to be honest.

Up to 14V of course but above it, I've never experienced on any of my porsches, or any other car for that matter.

rdodger · 4 Jun 2018

Apart from your choice of music, that all looks normal to me.

As mentioned earlier, is there a tracker that pulses?

cvega · 4 Jun 2018

Sorry about the music, blame Radio1

I'm more of radio 4 person, old..

I don't know where to look for the tracker. Can i verify that on the options list perhaps? When i was watching the meter (albeit not too closely), I didn't see draw go up and down. It was sitting at 34-37mA steadily.

A bit lost here...

The battery definitely loses charge, goes down to 11.5-ish after 4 days. It still cranks but it's on the verge of dying then. It's possible that i've not noticed it before fixing the alternator and on the old battery. Now that it _should_ all be fine and it isn't i started paying more attention.

I've used a generic skoda voltage regulator rather than replacing the whole alternator. Is there anything that can be connected / done wrong during changing the regulator? It seems to charge OK whilst its running...

andy1985 · 4 Jun 2018

Has the battery been checked/tested? If you can't find a current drain then it's either something waking up when it shouldn't be or the battery has a dead/dying cell. I'd opt for the latter.

My range rover had pretty much the same symptoms, run it daily and it was fine, leave it for 2 to 3 and it needed a jump.

cvega · 4 Jun 2018

I'd hope a brand new battery isn't shagged... I'll get it tested for a peace of mind.

battery drain.. but no drain? doing my head in

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