fpena944

Argh I'm so frustrated with these ongoing battery drain issues.

A few weeks ago I wrote about my car not starting one day. Had the battery and charging system tested and it looked fine. I hooked up the car to a tender since I wasn't driving it as often and didn't have any issues.

But lately I began driving more often again. However one day last week the car would light up the dash but not turn over the engine. I jumped it and promptly went to the local parts store to buy a new battery even though the one I had was only a year old.

All was good until yesterday. The new battery again lit up the dash but couldn't start the car. This was after using the car the day before and putting over 20 miles on it. I hooked it up to a charger and then today proceeded to test everything.

The battery itself is now fully charged so it started the car. I tested voltage when the car was on and it was 13.6 at idle with nothing on and about 12.8 with headlights, radio, and A/C on. Running the engine brings it back up to about 13.5. So that seems fine, right?

Then I disconnected the battery and wanted to check out the draw when the car was off. Right after running the car was pulling around 2.65 amps for about 10 minutes. Then this is where it gets interesting. Now when I hook up my multimeter it'll show a quick spike anywhere from 2-5 amps but then within 5 seconds drops down to a steady 0.01 draw. Is this normal? From that point it will stay at 0.01 amps until I disconnect the clamps. When I reconnect it again spikes for a short period of time and goes back down to 0.01

So WTF can I deduce from this? Based on what I'm seeing the battery should NOT be draining so quickly. Sure I have quite a draw when I first stop using it but from that point on the draw is pretty low. Is the spike when I reconnect something to be concerned about?

After starting the car if I do for an extended drive the battery does charge so I think the alternator should be fine. But something, somewhere is killing my battery and I can't figure out what or how to track it down since the draw ends up being minimal after I begin testing it. Any ideas? Help!

DBJoe996

Make sure the grounds, one in the frunk and one on the engine are clean with absolutely no corrosion. Not sure about the spike in amps...but what happens when you lock the car? When you shut down, get out and close the door the DME remains in ready mode. However when you lock the car it goes to sleep (in a manner of speaking). Also, are any of the lamps staying lit? Frunk and engine lid light come to mind. Also, it could be a problem with your alternator. Maybe an old voltage regulator on it's way out. Electrical problems are a PITA to figure out. Just my suggestions on where to start.

gnat

Technically OK, but right about 14 with the engine running would be better. Maybe the stator is starting to go in the alternator?

I don't understand. You disconnected the battery while the car was running? If so thats a big no no on modern cars as it can damage the electronics.

If the car was off and you disconnected the battery, there wouldn't be any draw to measure...

When you are "hooking" it back up, what was the state of the car up to that point? Did you have to unlock it? Open the hood? Open a door? Use the remote? etc..

I haven't checked the 996 and I don't hear anything from it, but I know both the Cayenne and BMW continue to run things for awhile after you shut them down. They eventually go to sleep, but as soon as you disturb them (open a door, etc..) they wake up some stuff even before you put the key in the ignition. Could be that the 996 does some of the same stuff.

I'll try to remember to take my ammeter out in an hour or so and get some readings of ours for you and see what I get.

fpena944

Thanks for the quick response.

Grounds are pretty clean as I don't see any corrosion anywhere. Alternator is about 4 years old but as appears to be charging okay. Plus wouldn't the ground or bad alternator show up on my voltmeter as excessive draw or low voltage?

I suspected the frunk light early in the process so I recorded a video on my cell phone and found that it does turn off once I close the lid.

As for what it does when I lock the door. In that case the spike is at about 0.35 A and then it goes down to 0.01 A as it was doing before.

Thanks again for the suggestions.

gnat

There are two important parts of the alternator. The voltage regulator and the stator. The first is what will show up on your volt meter and if it is going bad you will see wild fluctuations and going outside of the normal 13.5-14.5 range. The stator impacts the amperage that is being put out under different loads and it is typically diagnosed by measuring its output with an ammeter at various RPMs. If your stator is putting out less amps that your system draws, it can't charge the battery and the battery runs down.

Unfortunately the age of the alternator isn't a great indication, especially if you have an issue somewhere else in the system (e.g. short). I went through 4 high output (250A!) alternators in 18 months in my old Escape where the stator kept frying on me. I had a short somewhere in all the extra gear I had installed, but I never found it

alpine003

You can always start pulling fuses in the different groups(locking system, radio, lights, etc) and observe the voltage again.

Rubik

I smell a short somewhere.... Like Alpi says, start with an elimination process and one by one rule out different things. Of course, this also has its limitations.

fpena944

The whole problem I'm having with diagnosing this is that once the leads are hooked up for more than 5 seconds the draw drops down to 0.01 amps. If it would remain constant then removing fuses would be great for troubleshooting because then I can figure out what is pulling the amperage. Just stumped as to what I can do aside from taking it to the dealer for service.

I don't think it's the alternator because I can jump the car, come back from a 30 minute drive, and test the battery and it does show it is fully charged. Unless the alternator can pull from the battery when the car is off and I can't spot that on my multimeter?

gnat

So this is what I found with our 01 C4 coupe:

Came out, unlocked it, opened a door, popped the hood, and connected the ammeter to the negative cable:
At 5 minutes the the frunk light is still on and it's been reading between 1.77A and 1.82A and mostly at 1.80.
At 7 minutes it's falling off and around 1.73A now. Does the frunk light timeout?
10 minutes and it is still 1.72A with the light on. Battery is a steady 12.53V.

Locked car with the hood open:
Jumped to 4 point something and then dropped back to 1.8A after the "hood is open still" beep.
5 min = 1.74A
10 min = the frunk light finally went out and it's reading 0.18A

Unlocking Caused a jump to 11A, hung at 4.2A for about 30 seconds, then back to 1.8A.

Open doors and engine bay = 4.2A

Ignition on (no crank) with AC and stereo off: 8.35A

Lights, stereo, AC, defroster, and seat heaters: 63.2A

Engine running with everything on:
Idle: 5-9A in the hole
2k: 16-20A charging
3k: 16-20k charging

All acc off:
Idle: 25A charging
2k: 23A charging
3k: 23A charging

I forgot to get another reading (my wife came out demanding to know what I was doing to her car and distracted me), but at idle with everything on the volts were reading under 13. This makes sense as it was still discharging under that load. The dash volt meter went up to about 14 when I came off idle and when I turned everything off at idle.

When I connected the ammeter (clamp style), I did see a spike like you mentioned. I think that is just an effect of the Hall effect sensor.

Of note is that we have an aftermarket stereo with 2 amps so our "everything on" will be higher than usual.

Hopefully that gives you a baseline to check yours against.

Rubik

If I removed the guts of my wife's car and gold-plated it, she would be just as suspicious.

gnat

Well played sir. Well played


In reality it has more to do with the mess I made of my Escape's electrical system...

Rubik

Don't be too hard on yourself bud. After all, it was an Escape.

Paul Waterloo

It does not sound like your alternator or charging system has faults.

0.01 amps after a few minutes....it doesn't really get any lower than that.

There is a large draw that is happening when you are not measuring that is drawing the battery down, or your Y cable is causing it not to start.

When the car won't start, what is the battery voltage before you charge it?

gnat

Hey! Other than the alternator I loved that car. First car I had more than 3 years. Replaced it with the 958d and I still get misty every time I see it (gave it to her dad).

Ahsai

The spike is normal (DME and other electronic modules restart). 12.8v with load at idle sounds like bad alternator or the "y" cable to me. Normal is 13.5 to 14.5 at all times with load even at idle. To diagnose it properly, you need to perform volt drop test to see where you lose the voltage.

When it doesnt start, are you sure its the battery and its not something else like your clutch switch?