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?!!?HABBA BABBA??!!
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2,757 Posts
Discussion Starter · #1 ·
Ok...so as of the past little while, if my supra sits in the garage for a while, the battery drains. I have replaced the battery with a brand new one...same thing...if it sits in the garage for a while with no driving the battery drains. I can jump it off, and drive it...it may be fine for a couple of days and then be drained again.

Well a couple months ago, I took it to the local car get together. Sat in traffic and the car begin to want to die in traffic ...it would get so weak that my lights would dim, and the battery check light would kind of illuminate until I stepped on the gas some. It kept doing this all night until I took it home. Then after sitting a little bit the battery would be drained again. I suspected my alternator was probably toast, so I took it to an alternator repair shop the other day. They put it on the tester, let it even run for 20 mins and it was showing good charge...so now I am at a loss as to what could be going on or why the battery drains or gets so week...any ideas of where to begin to look if not the alternator??
 

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Always hungry!
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202 Posts
I dont have an answer, but i say either DC the battery or use a battery tender while not driving. My first year of ownership i also thought i had a weak alternator and i did go through 5 battery's within one year. The problem was, i would let the car sit for a week or two without turning her over, but now i know better! It seems the mkiv is a battery whore if not driven daily!
 

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The Great Kruso
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3,875 Posts
I don't know about that... I personally have left my car in the garge for over four weeks and it's cranked right over without any issues. I was also using the Red Top Optima battery which I've been told is not the best either by several people.
 

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?!!?HABBA BABBA??!!
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2,757 Posts
Discussion Starter · #4 ·
im just using the basic run of the mill battery, but I still cant believe the battery could be the issue surely if its not the alternator.
 

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Found E85 NOT in NJ!
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5,252 Posts
Red Tops are not bad, just different. They aren't deep cycles like the Yellow Tops so when they drain, they can only be brought back to life via a trickle charger BUT will damage the battery.

I personally am going with a yellow top so I have the ability to deep cycle the battery, for my Galant at least.
 

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Registered
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13,581 Posts
im just using the basic run of the mill battery, but I still cant believe the battery could be the issue surely if its not the alternator.
do you have AEM? If so, look at post #721 and related posts about "...vampire power draw..." in this thread http://www.supraforums.com/forum/showthread.php?515009-Gen2-AEM-for-Supra/page29

I don't know if what's in that thread relates to my problem or not, but ever since I got AEM v2 if my car sits more than a couple days it won't start on the battery (also Optima Red Top). For the last ten years prior to this I never had a starting problem even if the car sat for a couple weeks or more.
 

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?!!?HABBA BABBA??!!
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2,757 Posts
Discussion Starter · #8 ·
no...just what ever is factory. I do have an amp in the car, but its been in there a long time. I am running a map-ecu though on dual fuel pumps...not sure that would have any issue with the draw.
 

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Time for change
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6,866 Posts
On my Odyessey battery with the Factory Alarm activated I'd get like 2 days before the battery was a useless paperweight.
5 days if it was warm out without the factory alarm on. Tested the voltage draw it was within spec, those little batteries just don't have huge amount of amp hours...
On a fresh battery, You should be able to get a couple of weeks with no problem with no factory alarm on.
 

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director
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177 Posts
You need to put an amp meter between the battery and positive lead to see the amp draw at rest. If this is above 50 mA+ there is something in the circuit with a constant pull. In that case you can start by unhooking power to aftermarket add ons such as amp, alarms ect untill this is almost 30 mA draw or less. if none of this drops the amp then you start pulling fuses until you see a change. At that point you diagnose whatever is on that circuit by using a wiring schematic.
 

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Engmaineer
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2,406 Posts
For me for some reason the circuitry that controls the doom light was pulling enough current (mili amps) to where if the car sat for a week it was dead.


Also for my alarm a small LED on the dash that blinked was draining it for me also. I put a battery disconnect on the car so when it stays for long periods its fine.

Or get a battery tender.
 

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I <3 MSB
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330 Posts
the circuitry that controls the doom light was pulling enough current (mili amps) to where if the car sat for a week it was dead.
Is a doom light a JDM option? Sounds awesome!

OP, I had this happen to me, too. In my case, I thought it might be parasitic draw from the after-market alarm which had just shit itself. Then the starter stopped working and the usual tricks couldn't get it to start even once. At that point, I gave up and brought it to the local dealership, where they found gnawing on the harness leading to the starter. Possum had found its way into the engine bay and chewed on wires after running through its stash of dates...
 
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