What is a normal car battery drain for Ford Escort LX 1998 when everything is off?

Tiny
MAZATOV
  • MEMBER
  • 1998 FORD ESCORT
  • MANUAL
  • 130,000 MILES
Hi, I have a Ford Escort LX 1998 stick shift version. The battery was replaced recently ( 3, 4 months ago). The car battery has been dying frequently so measured the drain from the battery when everything is off. I measured around 200 mAmps. It seems a little bit too much, considering in this car's doors, windows, seats, etc are all manual. I measure around the same drain when the radio is off too. So I wanted to ask if this drain is normal for my car or does it mean I have a problem?

Thanks,
Mike
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Sunday, June 26th, 2011 AT 9:29 PM

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Tiny
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Anything over 30 milliamps is excessive
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Sunday, June 26th, 2011 AT 9:37 PM
Tiny
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Hi, here's some additional information in case anyone has any idea.
I checked fuses to see which ones make the battery drain. I had a big drop in drain for the following 2 fuses:

OBD II - around 40 mAmps
BTN - around 150 mAmps

I'm not sure what they exactly correspond because it's not in the manual but any help would be really appreciated.

Also I decide to test the battery on just holding the charge when it's disconnected. I fully charged it in my apartment and left it there measuring the voltage from time to time.
Here's what I got. Right after charging the voltage was 12:37V

Monday 9:45 am 12.37 V
Monday 6:30 pm 12.24 V
Monday 10:00 pm 12.22 V
Monday 12:00pm 12.20 V

As I understand just 12.37 V for a fully charged battery is not enough and also it shouldn't change with time when battery is disconnected. I figure this is substantial drop, right?

AAA won't replace it because this is their new battery and they say everything is fine with it but this is defintitely wrong, right?

Thanks
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Tuesday, June 28th, 2011 AT 3:55 AM
Tiny
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What you're seeing for a drop in voltage is insignificant. A fully charged battery will read close to 12.6 volts. A good but discharged battery will read close to 12.0 volts. You're right in the middle which suggests it's not fully charged yet. You also have a "surface charge" that you are reading at first. As the electrons get absorbed into the lead in the plates, the voltage will go down a little. Removing that surface charge to get a more accurate reading on the battery's condition is why the mechanic will put a high load on it for a few seconds, wait a bit for it to recover, THEN perform the actual load test.

Since you appear to understand electrical theory, it might make sense that a battery charger will not exhibit the same characteristics as when the battery is charging in the car. Chargers put out a rectified single-phase sine wave but generators put out a more steady rectified three phase output. For a large percentage of the time, a charger's output voltage is less than 12 volts, and it even hits 0 volts momentarily so it takes a lot longer to charge the battery that way.

Getting back to the problem, a 200 milliamp draw is way too much. Chrysler says 35 ma is the maximum allowable and at that rate they guarantee a good battery will still start the engine after sitting three weeks. Other manufacturers use similar specifications. Some go as high as 50 ma, but 200 is too much. Regardless, that will not kill a battery overnight. I don't know what a "BTN" fuse is for but if it's related to a computer on the car, some of them have to time-out before they go to "sleep" mode. Until they do that, they could draw as much as three amps for up to 20 minutes. There's a special procedure for measuring current draw on those cars because the measurements have to be taken after all computers have turned off, and disconnecting a battery cable to insert an amp meter will wake those computers up again when the cable is connected.

What I'd recommend first is to measure the current draw after 30 minutes to see if it drops lower. If it does, consider that normal. Next, test the charging system by measuring battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, the battery will not fully charge. If you find it's a little high, have a load test performed on the generator with a tester that measures ripple. Most professional testers do that. If there is one bad diode in the generator you will lose exactly two thirds of the rated capacity. That means a 90 amp generator will only be able to produce about 30 amps. That's just enough to run the fuel pump, ignition system and injectors, a few lights and the radio with nothing left over to charge the battery. With all other electrical loads turned off, the clue to a bad diode is the battery voltage will be a little high because the voltage regulator is responding to the drop in output due to the one missing phase of the three. Output voltage drops real low one third of the time and the regulator responds by boosting output. It takes too long to go back down during the two good phases so they put out more voltage than desired. Even though the average voltage is too high, the system can't maintain it when you turn on more loads such as the heater fan, head lights, and wipers. A bad diode will show up as very high ripple voltage.

If the voltage is too low, look at the voltage regulator on the back of the generator. It's held on with four screws in a rectangular pattern. In addition, there are two identical-looking screws corresponding to the two brushes. One might have a gray plastic cap covering it if it hasn't fallen off yet. The other one has an arrow pointing to it with the words "Ground here to test". As you stand behind the generator looking at the rear, with the two screws at the bottom of the regulator, that one that you want is the left of the two. If you use a piece of wire to ground that screw while the engine is running, it will "full-field" the system by bypassing the voltage regulator. Only do this test long enough to get usable results and do not raise engine speed as there will be nothing to limit output voltage. That voltage can easily go high enough to destroy computers and burn out light bulbs. Also, only do this test if system voltage is low. When there is no change in battery voltage between engine stopped and running, this test identifies whether the generator or the voltage regulator is the cause. If the voltage is around 12.6 volts with the engine running, and grounding that terminal has no affect, suspect a worn brush. New ones come as part of a new voltage regulator. They can be unbolted but I never checked to see if they can be purchased separately.

The more common problem is the battery voltage is around 12.6 volts and grounding the test terminal makes it go well over 16 volts. That is proof the regulator is defective and the rest of the generator is working. It can be replaced separately by removing those four screws. On most front-wheel-drive cars that can even be done without removing the generator from the engine.
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Tuesday, June 28th, 2011 AT 8:56 AM
Tiny
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Hi,

Thanks for such a thorough reply. I'm gonna try to check those things that you suggested. I took my car to autozone and then to a mechanic and they couldn't find anything wrong with the car. That's why I got to the conclusion that it's either a battery or some drain that's really hard to find.

I was kinda confused about the battery part that you wrote. The battery charger said that the battery was fully charged but it was giving only 12.37 V (not 12.6V). Also during the last two days(2 days after charging it ) the voltage on disconnected battery already dropped to 12.1 V which as I understand is really close to discharged battery (maybe like 25% charged or smth like this ).

Yes, the speed of discharging was decreasing but isn't 12.1 V too low? From what I understood from forums and from mechanic that I went too if you disconnect the battery it should hold the charge for a very long time(at least two weeks), but with this one it dropped to 12.1 in two days.

Thanks for reply!
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Wednesday, June 29th, 2011 AT 5:43 PM
Tiny
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Here's some drawings I made to explain ripple and how it differs between a battery charger and the generator on the car. If it doesn't make sense, don't get all wrapped around the axle in trying to figure it out. I suspect the tiny drop in battery voltage you're seeing is irrelevant to your problem. Rather than testing the voltage after putting the battery on a charger, let it charge in the car while driving a good 10 - 20 miles, then stop the engine and disconnect the battery. Measure the voltage a few minutes later and again in a day or two. My guess is it will be higher than 12.1 volts. Recheck the charging system voltage too at some point.
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Wednesday, June 29th, 2011 AT 10:14 PM
Tiny
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Hi again,

First of all thanks for the replies and your explanations it was very helpful!

I checked the voltage when the car was running it was around 14.3 V.

Also I tried disconnecting the battery after driving it for a while. You were right, right after driving the voltage was 12.6V. But it was still dropping after I would disconnect the battery and it would drop to 12.15-12.10 V in less then a day. What do you think this means?

Also I bought the battery switch off and connected it to my battery. I wanted to ask if it has a difference if I connect it to the positive or negative terminals of my battery. I saw different suggestions online but didn't really understand what's the difference. As of right now I connected it to the negative terminal.

Thanks, Mike
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Tuesday, July 5th, 2011 AT 3:04 PM
Tiny
CARADIODOC
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Doesn't matter where you put the switch. You're working in a series circuit so a switch or anything else that causes a break will have the same effect anywhere.

Here's the "story" I gave my students because electrical theory is very hard to understand for people who work best on things they can see and touch: Imagine water flowing down a river. It flows to the ocean, evaporates, a cloud floats back up over the land, gets torn on a church steeple, rain falls out and trickles into the river and starts all over again. That is like a giant series circuit. It doesn't matter WHAT you do; anything that stops that sequence of events stops the flow of water. You could put a dam on the river, or you could put a huge sheet of Saran Wrap over the ocean so the water couldn't evaporate. The cycle can be stopped anywhere.

In your car, current flows from the battery positive cable*, through the fuse, through a switch, a light bulb, to the body sheet metal, through the negative battery cable, and back into the battery. That is a complete series circuit. A break anywhere in that circuit will cause the current to stop flowing just like the water stopped flowing in my story.

*Now, before anyone tells me I messed up, current actually leaves the battery's negative post and comes back on the positive post, but it is customary to draw electrical diagrams starting from the positive post. That is a technicality that has no significance and makes troubleshooting those circuits easier to understand.
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Tuesday, July 5th, 2011 AT 7:47 PM
Tiny
DOCFIXIT
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Pardon the interruption but Mike the battery is toast. It has plate damage and is internaly draining
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Tuesday, July 5th, 2011 AT 7:55 PM
Tiny
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Would you by any chance know a place where I can get that checked and get the paper saying my battery is bad? They won't replace unless I prove them that it's bad.
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Friday, July 8th, 2011 AT 4:03 PM
Tiny
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I suspect the battery is going to test fine after charging it. You would have to leave the battery with the mechanic, or the whole car, so they can retest it after a day or two of being disconnected and not charging.
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Saturday, July 9th, 2011 AT 12:15 AM

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