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Forum Index : Microcontroller and PC projects : Nothing to do with uC: measuring parasitic draw from car battery
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thwill Guru  Joined: 16/09/2019 Location: United KingdomPosts: 4036 |
LOL, it has 4 (5?) wheels and it goes "Brmmm!" (pretty much all I've ever asked, beyond a little reliability, from a car). This is a 10 year old car which is about as "low rent" as they come, I doubt it has much in the way of "sensitive ultrasonic sensors". Anyway, I'm gratified to know more about it now such that if I had no other option I might be able to poke about with some hope of success. However given it wouldn't take me < 3 hours that I don't have, plus probably at least one trip to Halfords, plus the risk of damaging car or multimeter I think I'll be taking it to the mechanic; if I could stand on the roof of our house I could throw stones and hit at least two  .Thanks again folks, Tom Game*Mite, CMM2 Welcome Tape, Creaky old text adventures |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Disconnecting the car battery does not give you information how to fix. It is 2 things 1/ a weak old battery. Measure the volts during engine start. When it goes down to 9 volt, replace it 2/ something eating power. Through the fuse box you get an idea where to look. Volhout PicomiteVGA PETSCII ROBOTS |
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| twofingers Guru Joined: 02/06/2014 Location: GermanyPosts: 1241 |
Hi Tom, my guess: you should save up for a new battery!  edit: To be clear: the battery is destroyed, buy a new one! Measuring with a 0.1 ohm resistor is a good idea (as long as you don't try to start the engine  )Good luck! Michael Edited 2024-08-16 21:03 by twofingers causality ≠ correlation ≠ coincidence |
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Rickard5 Guru Joined: 31/03/2022 Location: United StatesPosts: 463 |
This may sound stupid but does England Still have that Annoying Positive Earth thing on modern cars? I may be Vulgar, but , while I'm poor, I'm Industrious, Honest, and trustworthy! I Know my Place |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3800 |
If buying a battery I recommend www.tayna.co.uk John |
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| DaveJacko Regular Member  Joined: 25/07/2019 Location: United KingdomPosts: 76 |
Rick I'd totally forgotten about the positive-earth thing ! wasn't it changed to avoid electrolytic corrosion ? By the way your American switches are all upside down ! Joking, Actually, that way, swipe down to switch off, makes more sense. easier to turn machine off as you fall, stunned, to the ground. |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2914 |
GDay Tom, All, Just pop out a fuse and put your multimeter across the terminals in AMP mode. Record the reading and go to the next etc etc etc. If you see a reading that seems high then you should also know the area to be looking. These cases are usually 3rd party car alarms or entertainment equipment powered off a permanent 12V rather than a switched AUX 12V that should be off when the car is off (and locked). You could use an old blown fuse and solder wires to it to connect your meter. Regards, Mick (The big one) . Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3800 |
Sadly that tends to wake modules so you get current flow that's not the fault but looks like it could be. John |
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PeteCotton Guru Joined: 13/08/2020 Location: CanadaPosts: 368 |
Had a parasitic draw on my old Ford Expedition. It took ages to track it down, but it turned out that the rear windscreen wiper would occasionally seize in the non-parked position, and the motor would just keep driving trying to push it to the parked spot. Even after I fixed it I had to replace the battery - as it was damaged. |
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| Rickard5 Guru Joined: 31/03/2022 Location: United StatesPosts: 463 |
NO Dave I Swear positive Earth was Created to sell me Radios and Magnetos Most of our switches are up=on , down-off Now I will agree we do fail to follow British electrical code our switches only have off and on, No Smoke or Fire ;) I may be Vulgar, but , while I'm poor, I'm Industrious, Honest, and trustworthy! I Know my Place |
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OA47 Guru Joined: 11/04/2012 Location: AustraliaPosts: 926 |
Many years ago I had a work vehicle (1985 Ford Falcon Station wagon) that was not used on the weekends and occasionally I would have a flat battery at the start of the week. When I parked it at the end of the week I regularly grabbed the multimeter and measured the current drain from the battery and eventually I found a 500mA draw when parked. I started lifting fuses and relays to track it down and located the fault to a sticky relay that operated a heater element in the carburetor for cold starting. It took weeks to catch it but I was glad when I did. 0A47 |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6780 |
@Rick No, positive earth has gone the way of the dinosaurs in the UK now. If you do come across it it will be on some lovingly restored collectors car. Can we help it if you lot are incompetent enough to install your switches upside down? Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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