How much current your car draws while sleeping?

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  1. #1
    CelicaSupra.com Member RedP85's Avatar
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    How much current your car draws while sleeping?

    Early this summer, my battery died.
    (batt did not have enough juice to crank after a 2 hour drive).
    So I replaced it with a nice AGM, size 27F.
    Went to a few show & shine, then back in the garage.
    Well, after about 3 weeks, dead battery again.
    Fully recharge and drove an hour.
    Back in the garage, I decided to check the current the car draws when sleeping.

    I measured 27 mA between body and neg post.

    I would like to have numbers from others MK2.

    I will be doing investigation next winter, but am curious of what a non-issue car takes / what am I targeting to.

    PS: you will most probably loose time & radio station doing so.

    Thanks in advance.
    -Jocelyn,
    P85-6MGE SDR(HKS kit c/w IC and F-Con in a box) 225KKm, NAL seats, 2.5 Brullen, ACT clutch, LJM, SS lines, Trip Computer. EuroH4
    P85-5MGE SDR had 439KKm (for 17 years my daily driver, RIP...), 2002 E39 ///M5 LMB Hidden Content
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  3. #2
    CelicaSupra.com Member supraz's Avatar
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    I will be doing work on my '83 tomorrow and I have to disconnect the battery so I will get a reading for you.

    Having said that, a 27F battery, not AGM should be rated at 66-110 Ah.
    3 weeks is 504 hours.
    27 mA is 0.027 A
    504 h * 0.027 A
    Total draw for this time period should be about 13.6 Ah so there should be oodles of capacity left in three weeks.

    Something sounds off.

    Dale
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
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  4. #3
    CelicaSupra.com Member ddd228's Avatar
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    Please be aware that lead-acid batteries SELF discharge. A maintainer is a great idea.2 A is fine.
    Your alternator should provide 14 volts AT the battery.13.7 is good.
    Your discharge leaks may be caused by multiple electronic devices.
    Alarm systems and KEEP ALIVE memory in other things.
    If you remove the negative terminal,you will loose your radio pre-sets and possibly confuse the ECU.
    NEVER do that to a late model automobile.Mercedes,BMW and more.

    (To find the current draw,start pulling fuses to everything.)
    First,use a test light and connect the lead terminal to the disconnected negative post and see if it lights up. If not,you are good to go.
    If it lights up,start pulling fuses,until the test light goes OUT.

    I had a Corvette in the shop and the door locking solenoid was causing the draw!
    Dave in Seattle. I keep LATE hours.Hidden Content
    '84 type "L" ,Auto ,daily driver. Dk blue.

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  6. #4
    CelicaSupra.com Member supraz's Avatar
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    I recently had to replace my alternator because the rectifier diodes were leaking BADLY. I would take my battery charger off the battery and I could see the battery voltage drop by 0.1 volts in a minute! The battery would drop to 6 V overnight. I replaced the alternator and the problem went away immediately.

    I would assume that leaky diodes allow current to flow from the battery through the diodes in the alternator to ground.

    I was lucky because the problem was so obvious I could spot it. If it was more subtle I wouldn't think of this.

    I don't think that you will see current from battery negative to ground show up on this path. I think you WOULD spot it if you measured from battery positive to the wiring harness. The alternator is an alternate ground if the diodes are leaking.

    Just a thought.
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  7. #5
    Boosting Mod SilverMk2's Avatar
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    If you don't drive your car a lot you should spend the money and buy a CTEK charger. They come with a wire harness and you connect it to the battery and run it down to the grille somewhere. Then just plug the car in every time you park it. I have one on my car and you can let it sit for months and it will fire up everytime. They're a little pricey, but well worth the money IMO.

  8. #6
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by SilverMk2 View Post
    If you don't drive your car a lot you should spend the money and buy a CTEK charger. They come with a wire harness and you connect it to the battery and run it down to the grille somewhere. Then just plug the car in every time you park it. I have one on my car and you can let it sit for months and it will fire up everytime. They're a little pricey, but well worth the money IMO.
    I use a charger with clothes pin type connections to keep my cars charged, but using a permanently attached connector that is a simple plug in connection would be a lot easier.
    Where do you have the connector located so that you can plug it in easily without opening the hood and yet not have it stick out like a sore thumb?

    If you have pictures, I would love to see it.

    Dale
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  9. #7
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    Not quite on topic, but in my experience, AGM batteries don't play well with older cars because their alternators don't put out enough voltage to fully charge the AGM. Running around on a partially charged battery all the time seems to shorten their lifespan really quickly. Look at most modern cars with an AGM and you'll see charging voltages between 15-16v. Even my 07 FJ can't handle the AGM without me keeping it topped off via charger pretty often. Tried a number of them on previous 85 Celicas with horrible results when not charged via AGM-specific charger regularly.
    85 P-Type, White over Maroon Leather, bone stock

  10. #8
    Boosting Mod SilverMk2's Avatar
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    Quote Originally Posted by supraz View Post
    I use a charger with clothes pin type connections to keep my cars charged, but using a permanently attached connector that is a simple plug in connection would be a lot easier.
    Where do you have the connector located so that you can plug it in easily without opening the hood and yet not have it stick out like a sore thumb?

    If you have pictures, I would love to see it.

    Dale
    I don't have any pics, but it runs thru the gap around the radiator and over to the drivers side of the lower opening. With a zip tie or two along the way. It hangs down a little bit, but typically gets blown inside the opening once you start driving it. I think they also make one that plugs into the lighter socket if you don't mind going inside the car.

  11. #9
    CelicaSupra.com Member supraz's Avatar
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    Quote Originally Posted by RedP85 View Post
    Back in the garage, I decided to check the current the car draws when sleeping.

    I measured 27 mA between body and neg post.

    I would like to have numbers from others MK2.

    I will be doing investigation next winter, but am curious of what a non-issue car takes / what am I targeting to.

    PS: you will most probably loose time & radio station doing so.

    Thanks in advance.
    10.1 mA between negative post and body. The same between the positive post and the wiring harness.
    Black 1983 P Type 5 Spd, Cloth Interior, BBK,HRE 17" Wheels, HKS Exhaust
    White 1984 P Type Auto, Leather Interior, Sunroof, Digital Dash

  12. #10
    CelicaSupra.com Member
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    Quote Originally Posted by Speedrye View Post
    Not quite on topic, but in my experience, AGM batteries don't play well with older cars because their alternators don't put out enough voltage to fully charge the AGM. Running around on a partially charged battery all the time seems to shorten their lifespan really quickly. Look at most modern cars with an AGM and you'll see charging voltages between 15-16v. Even my 07 FJ can't handle the AGM without me keeping it topped off via charger pretty often. Tried a number of them on previous 85 Celicas with horrible results when not charged via AGM-specific charger regularly.
    This is absolutely true. It's also another one of the benefits of upgrading to the 92 Camry alternator. It's charging voltage is about 14.5 vs about 13.8 with our original alternators. There are ways to increase the charging voltage of (older) alternators by using certain pairs of diodes in the reference voltage line to make the voltage regulator think that the system voltage is lower than it really is. Each set of parallel diodes in series with the reference lead increases the charging voltage by about 0.6 volts. This mod isn't hard, but it's not something to be undertaken unless you really understand exactly which components to use and how to properly connect and protect them. If anyone is interested in doing this, a Google search should provide a source for device specs and complete directions.

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