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Old 02-19-2013, 07:39 AM   #1 (permalink)
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Most likely cause of battery drain?

So I am going to be trying to hunt down the cause of my battery drain in my S4. I imagine it is the factory alarm system but I really don't want to remove it as it works well and I have integrated a keyless entry system that also activates/deactivates the alarm when locked/unlocked. So, if that is the culprit, are there any options to make it stop the battery drain? I am not worried about the time that it is armed. The drain occurres while it is parked in the garage with the alarm off. I already have a battery tender installed but would rather not have to keep it plugged in all the time.

Otherwise, any other items I should look at as being the source of the drain? Any advice of searching for the source of the drain? I imagine connecting an ampmeter between the battery and the main power wire and start disconnecting things until I see the amps (miliamps) drop to nothing?

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Old 02-19-2013, 07:53 AM   #2 (permalink)
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the normal method is to put an amp meter between the battery post and the cable and then remove fuses until you find the drain.
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Old 02-19-2013, 07:59 AM   #3 (permalink)
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Thats the plan then!

Thanks!
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Old 02-19-2013, 11:56 AM   #4 (permalink)
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the normal method is to put an amp meter between the battery post and the cable and then remove fuses until you find the drain.
That was well and delicately stated.
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Old 02-19-2013, 01:00 PM   #5 (permalink)
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I could see a failing alternator voltage regulator could cause a drain (possibly) as the black goo die-electric leaks out... maybe? Check on top of your AC compressor for a puddle of goo.
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Old 02-19-2013, 01:16 PM   #6 (permalink)
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New to my Esprit V8, so this is more a question than suggestion based on first hand knowledge.

I notice for the Esprit when you disconnect and reconnect the battery, the headlight pods cycle up and down once. I understand from archive posts this is normal on the Esprit. Sort of interesting behavior. Haven't looked into the wiring details yet. Pretty familiar with pod motor wiring options from adding them to my '69 Plus 2 to ditch the stock vacuum pods, and know some configurations can result in a parasitic drain. Wiring configuration I used has no drain and does not cycle like this, although it does not provide a 'Flash to Pass' feature.

Anyway, my question / concern... Might be best to check and remove the fuses controlling the pod motors & headlamps first in your checking sequence and eliminate them as a parasitic drain issue? Thought is that with your Ammeter set to (presumably) mA scale and in series with the positive battery post, you might fry the instrument if the high draw of the pod motors and headlamps kick in while fiddling with fuses and connection / disconnection of the battery?

As a go-by, my '87 BMW has this sort of constant battery drain, and it is completely normal at about 50 mA. This generally results in flattening the battery in about three weeks. No alarm, but remote locking.

Anyone got the normal constant draw for the Esprit handy? Is it generally around the 50 mA level?

Assuming some level of parasitic current is normal on the Esprit, you had a second question on options to mitigate. Again, for my Plus 2, I installed a remote controlled master shut-off switch on the positive battery terminal. This disconnects everything. It is on the positive side so that the internal latching relay is supplied with power. The remote is a key ring fob. A latching relay has no draw in it's 'latched' position; it only needs power when you engage or disengage it. The one I used is called a BatteryBrain; I think there are other brands available in the marine electrical world.

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I really like this set-up as the Plus 2 battery posts are buried under the trunk floor, so was a hassle to disconnect while doing service work. Disadvantage of this set-up is depending on the radio you have you may loose your pre-sets every time you turn it off; my Plus 2 radio has permanent memory so not an issue. Manual shut-off switches are common as well; similar but generally mounted on the ground side.

HTH
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Last edited by stugilmour; 02-19-2013 at 02:28 PM. Reason: Added about the latching relay shut-off
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Old 02-19-2013, 03:00 PM   #7 (permalink)
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...
Thought is that with your Ammeter set to (presumably) mA scale and in series with the positive battery post, you might fry the instrument ...
...
AMP meters are cheap enough.

The other non-fused gear is the alternator.
Or at least the fuses are in a different place.

If you loose a diode then that is a lot of current flow.
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Old 02-19-2013, 06:03 PM   #8 (permalink)
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When I have to go hunting for a current drain I use a light bulb in series with a battery lead. Pull the fuse for the door interior lights so you can leave the doors open while you look. On the Lotus you will not get the bulb to go out completely. When you are sure it is as dim as you can get it then you can get a meter and measure the drain. It will be high. The standby drain for the alarm and the ECU is a lot. What I do is if the car is not driven during a 2 week period (1/2 a month) I will put the Battery Tender on for 1 day. That is all that is needed to top off the battery. In the winter I remove the battery and then it only needs to be topped off 1 day every 4 weeks. I also do not like leaving a battery charger on continuously. I have also found that although the battery may not be dead, in 3 weeks it will be drained enough so that it will not crank fast enough to start. Having a chronically discharged battery is also very tough on the alternator. It will always have to work at high loads and that will cause it to run hotter than it should, aging it faster till the back goo starts dripping out. A battery master switch is not a good idea unless you run a bypass for the ECU and that would defeat the purpose for the master switch. Killing the ECU is not a good idea since it will have to rebuild the tables and relearn everything every time you shut the master switch off. Till then it runs cr-ppy. You *could* add a hidden switch to shut the alarm off, that might reduce the drain enough to live with.
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Old 02-19-2013, 06:59 PM   #9 (permalink)
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Anyone every try unplugging the alarm module? Curious how much of the drain that eliminates, or whether most of the drain is the ECM?
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Old 02-20-2013, 05:46 AM   #10 (permalink)
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Originally Posted by stugilmour View Post
Anyway, my question / concern... Might be best to check and remove the fuses controlling the pod motors & headlamps first in your checking sequence and eliminate them as a parasitic drain issue? Thought is that with your Ammeter set to (presumably) mA scale and in series with the positive battery post, you might fry the instrument if the high draw of the pod motors and headlamps kick in while fiddling with fuses and connection / disconnection of the battery?
Most handheld ammeters have a fairly small fuse which will blow. What you need to do is first to connect the ammeter (with alligator clips is best), then remove the battery lead. That way there is no current inrush as the circuits don't get interrupted. The negative side is usually easier than the positive.
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Old 02-20-2013, 05:56 AM   #11 (permalink)
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Disconnecting the alarm is a big deal. You must bypass the circuits for the immobilizer or the car won't start. You also lose the keyless entry function.
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Old 02-24-2013, 11:13 AM   #12 (permalink)
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My battery (new) drained completely after only 2-3 weeks of non-use. I didn't lock the car, so I don't think the alarm ckt. is the big drain.
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Old 02-25-2013, 12:55 PM   #13 (permalink)
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The alarm is always on no matter if you arm it or not. It has a radio for the remote key fob. The problem is if you disconnect the radio you enable the immobilizer. To disable that you have to jumper the starter and ignition circuits so you will be able to start the motor. The siren module also draws power charging it's internal battery so you need to disconnect it too.
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Old 02-25-2013, 01:38 PM   #14 (permalink)
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Parasitic battery drain around 50 to about 70 milli amps is classed as normal on OBDII era vehicles, its best just to plug in a battery tender when you are not using it to avoid having to charge up the battery from dead and have to re programme the power windows, sunroof, alarm etc.

Boosting is not a good idea on OBD II stuff as the little high output alternators will get hot and burn up charging a flat battery once the engine is running.
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Old 02-25-2013, 01:38 PM   #15 (permalink)
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Just have to plug in this car. Another one of the endearing features of a late model Esprit.
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Old 02-25-2013, 06:30 PM   #16 (permalink)
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I agree trying to disconnect stuff to extend standby battery life is futile. Newer cars have been modified internally to have a lower standby (sleep mode) battery drain but it is still a lot if you don't use the car for a few weeks. And when you do use the car you will always be putting a heavy load on the alternator trying to charge a chronically undercharged battery. Then you will see the black goo dripping out. The very best thing to do is if you do not drive the car for 2 weeks, you put a battery tender on it for a day. That way you will always have a fully charged battery and the alternator will thank you for it. on newer cars with OBD II it is no longer recommended to 'jump" the battery to get it going. Besides the chance of reversing the polarity and the spikes you will cause connecting and disconnecting, as posted, the alternator is not meant to *charge* the battery so much as to replace what is used to start the car and run all of the load while driving. You are supposed to either remove the battery and recharge it or switch the dead one for a charged one. On some cars, removing the battery is almost major surgery. Anyone see what you have to do to jump a hybrid? The starters aren't 12 volts anymore and live inside the transmission. In the not too distant future your jumper cables are going to wind up on the wall for decoration right next to the buggy whip!
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