Parasitic Battery Drain

[andyofcolumbusmerkur]

Ed, You won't measure anything with the probes like that.

A fuse is just a small strip of metal. Placing the probes across it won't measure anything. Unless it is a blown fuse.

To measure current the electricity has to flow through the meter.

The only way to do it is as I described previously.

You still may have a parasitic loss through the alternator and you have to test that separately as it is not fused in the fuse box.

False,
False
False, and once again False.

[brokencase]

Fine Andy, I'll correct the statement "You won't measure anything MEANINGFUL with the probes like that".

...as in MEANINGFUL for our discussion.

We are talking about a slow drain on the battery that takes place over the course of many days or weeks.
You are not going to find this type of small parasitic current drain by measuring the voltage drop across the fuses.
Unfortunately, these are the typical type of drains that show up on a 35 year old car. Old capacitor leakage, corrosion, etc..

You do agree with that?

I actually feel sorry for those who watch "The Humble Mechanic's" video and have slow drain issue and think they can take this approach to find it.
Like the guy with the Vette who posted in his comments. Not to mention the million other folks who think they can find even a significant drain with a Harbor Freight freebee meter using that method.

If anything the video should have a disclaimer in the beginning where he states "This method will not help diagnose slow parasitic drains that occur over many days or weeks, i.e., those less than 50 milliamps, furthermore a quality DMM is required".

Other than that, the video shows a fine approach to finding large large parasitic battery drains of the type that kill a battery overnight.
I just never have run into that issue outside of leaving a light on or leaving something plugged into the cigarette lighter. Have you?

[brokencase]

Brad - One thing I wanted to mention.

The Cigarette lighter voltage indicator itself depletes the battery. I left it in once and it killed that battery pretty quick, like a day or two.

[Ed Lijewski]

Since I have upgraded to an AGM battery (as well as the Titan alternator!) I find I can let the Scorpio sit for 3 weeks (maybe more) and still be able to start it.

This was not the case with a conventional battery and the old alternator. Maybe a week to a week and a half. In fact whenever I had to park it at an airport for a business trip I would disconnect the battery.

I recall measuring the parasitic loss with the meter and I think it was around 20 milliamps. I did not track down what all was consuming this but the usual suspects would be memory in EECIV, fuel computer, and radio.

Add to the list the overhead clock/day&date. (EATC too?).

So right there, four power eating "accessories".

Dean: this should be right up your uh alley.

Calculate (as best possible) the individual and total mAmp Hours/day required to.keep those alive, instead of looking for other possible current drains.

Add to that 10mAmp hour (generally accepted figure) estimated power loss in the battery itself even without any accessory drains.

Show totals for one week, two weeks, three weeks...

That likely will be enough to explain why some think Scorpio batteries "die" early and often.

Even without knowing what the total mAmpHours will turn out to be it's why I always connect my unused fleet to battery maintainers (not "tenders"...).

YMMV

[brokencase]

Yes. The only items I think would be drawing current when the car is off is the clock, the radio, the EECIV, the EATC and the fuel computer.
If you have installed a remote starter or door unlock then that too.

I have a spare overhead clock here on the bench that I picked up while at Carlisle. I just powered it up and it draws 4.36 milliamps.

Now, the clock circuit takes 12v in and then it goes to a little 5v regulator that feeds a 220uf electrolytic capacitor.
I pulled that capacitor off and swapped a new one in. I tested the old capacitor but it really wasn't that bad.

I re-tested the clock and it went to 4.35 milliamps. Within the error of the meter.

However if that capacitor had gone bad... and I have seen others in the EATC that have gone bad, then it could draw more current than when it was new. It could be significantly more.

FWIW, if you assume a similar draw for all the above stock items then 4.35x5 = 21.75 milliamps - which is pretty close to what I remember when I measured at the battery a long time ago.

[Ed Lijewski]

4.35x5 = 21.75 milliamps plus 10 milliamps natural battery degradation= 31.75 milliamps.

So there should be no surprise that after two/three weeks sitting the battery voltage reads 12.2 or less.

YMMV

[brokencase]

From the Optima Folks...
https://www.youtube.com/watch?v=-yPlx4MBNRU
Scroll to 2:00

Ed - calculating how long the battery will last knowing what the drain is is not that easy.
You might think that you could say that the battery is 50ah and calculate from that, but it really is when the battery gets down to the point where the starter can no longer crank over the engine. That is hard to predict and is well below the 50ah rating.

[Ed Lijewski]

I think we've arrived close enough to answering the essence of the question of "What's up with Scorpio batteries that see noticeable voltage degradation when left sitting?"

On Sunday I'll measure voltage in my '88 which I took off from a battery maintainer last Sunday (earlier post/photo). V was 12.7, I'm certain it'll be lower then.

But, we have evidence and reason to believe that the drain I'll find will be normal as that of other Scorpios, comprised of the Keep Alive Memories in the EEC and accessories cited above.

IOW, no cause for suspicion in each vehicle of abnormal voltage draws.

But as well, that will be confirmation of my longstanding practice of connecting every battery not being regularly used (i.e., sitting for more than a couple of days) to a battery maintainer.

In fact, best practice IME is to at least monthly connect even a often used vehicle battery to a battery maintainer. It's well recognized that anything under 30-45 minutes of highway driving doesn't fully charge the battery.

Even when a volt meter shows say 12.6/7v after a short trip the likelihood is that the battery is actually not at the same "full" charge as it will be after being connected to a battery maintainer over night (e.g.) providing the optimum slow charge and desulfation.

I have three battery maintainers and two battery chargers (I rarely use those but they're handy should faster recharging be necessary).

So any Scorpio owner with doubts should test for abormal parasitic drains. But also expect accumulated normal KAM voltage degradation.

YMMV

[brokencase]

I think it is wise for any Scorpio owner to at least pull the positive terminal, insert the DMM (set to milliamps) and see what the drain is.

I do have a maintainer, but I'll put it on only on the rare times when I don't expect to drive the car for a while.

The AGM in the Sprite is amazing. The Sprite has no parasitic loss other than the battery's own internal loss.
AGM batteries just seem to hold it over the long run. I can let it sit all Winter and it will still have 80% or more in the Spring
It will start the car fine, but I will typically throw the charger on it for about an hour and it is good to go for the rest of the season.

For this reason I decided to put an AGM in the Scorpio as well.

BTW Nice tool to have...
https://www.ebay.com/itm/133854294082

Tells you the condition of the battery and the internal resistance. That is not the exact one I have but the display looks the same.

[andyofcolumbusmerkur]

So much stuff brokencase says is either not accurate or completely wrong. Not just on this thread but on so many other threads as well. I guess there is just no helping him, his way or the highway.

[Ed Lijewski]

I wonder: does the ABS computer also draw KAM?

YMMV

[Ed Lijewski]

So much stuff brokencase says is either not accurate or completely wrong. Not just on this thread but on so many other threads as well. I guess there is just no helping him, his way or the highway.

But it's said with such authority....

YMMV

[milehighXR]

On my Scorpios, I could only leave them for 2 weeks untended(no battery tender, no driving) before the battery would be dead. And usually if it got dead, it was dead-dead. These were Optima red tops even. I never went thru to figure out where my drain was, but I did notice that my XR, or even my wifes 02 Venture, could sit for at least 3-4 weeks before killing a battery to a point that it needed replacement, I went thru so many free replacements 1 winter, that my parts store almost told me no more. Needless to say, any car that is expected to sit for more than 7 days without driving gets a battery tender.

[brokencase]

So much stuff brokencase says is either not accurate or completely wrong. Not just on this thread but on so many other threads as well. I guess there is just no helping him, his way or the highway.

Andy I am sorry you feel that way. I have above stated that I do stand corrected.

But I have also tried to explain to you that you cannot measure small milliamp current drains by measuring the voltage drop across the fuses.
This is the "truth" in regard to the context of this discussion. This does not happen by my authority, it comes from basic understanding of electronics. You seem to have ignored my response. Instead you give a frustrated response of "So much stuff brokencase says is either not accurate or completely wrong" without providing any specifics.

I am always willing to confront any incorrectness in my posts. Are you?

So go ahead. Explain to us all how you can accurately measure a 5-10 milliamp drain across a 30 amp fuse by the method you have found on youtube.

Show us how that method can track down what is causing Scorpio to kill its battery in two weeks versus three or four weeks.

Maybe you were wrong. Maybe you saw that youtube video and mistakenly thought that it was the final word on the subject.
Would you be humble enough to admit to that?

[Ed Lijewski]

After exactly seven days to the hour here are photos of tested Scorpio battery voltage.

I took four pics because on first touching the probes to the poles the meter read 12.2v. After less than a minute as I got the phone camera app ready to shoot voltage rose ranging from mid-12.40vs to mid 12.50vs (I briefly saw 12.60).

I assume this demonstrated the wisdom that, in cold weather especially, putting a load on the battery revives its potential to some degree. Commonly the suggested load is turning on the headlights for 30-45-60 seconds before trying to start the engine in zero or lower F temps. The multimeter load is really minuscule but it clearly stimulated a chemical reaction that produced a voltage increase.

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YMMV