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 Post subject: Parasitic draw 99T. HELP
PostPosted: Thu Sep 19, 2019 10:08 am 
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Joined: Sun Mar 13, 2016 2:49 pm
Posts: 28
Location: Dorking Surrey
Car Model: 99 turbo
The new battery on my 99T is going flat after about a week normally park up with battery disconnected so don’t think it’s the battery so tried obvious things first like taking bulb out of bootlight etc .
Borrowed a meter and stuck in on car to look for current draw ended up pulling out fuse 9 , That’s Clock
interior light and ciggy lighter . Now here’s the thing am i reading this right it’s 23milli amps . But it varies between 23 and 26 constantly , is that what a clock would draw ? Is that normal and am I reading this right . How long would 23 MA take to flatten a battery ?
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PostPosted: Thu Sep 19, 2019 10:47 am 
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Joined: Wed May 12, 2004 9:46 pm
Posts: 14949
Location: Mulbarton,Norfolk
Car Model: TTid's only now :-(
If we took the draw to be 25mA for simplicity.

the it would take 40hrs to drain 1 Ahr (1000/25)

with a 60Ahr battery, from fully charged to a theoretically zero charge would be 60 * 40 hrs, or 2400hrs (100 days, or just over 14 weeks)

Start looking else where...

You could/should be looking for a drain of 200-300mA I would think to flatten that battery in 7 days.

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PostPosted: Thu Sep 19, 2019 11:06 am 
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Joined: Tue Oct 30, 2007 9:26 pm
Posts: 6152
Location: North Essex
Car Model: 900Ruby,vert, 9000, 99, Sonett
Depending on the battery's capacity, it should last at least 4 months at that rate of discharge.

70 Ah battery: 70÷(23x1000)÷24 = 126 Days or just over 4 months.

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PostPosted: Thu Sep 19, 2019 11:45 am 
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Joined: Sun Mar 13, 2016 2:49 pm
Posts: 28
Location: Dorking Surrey
Car Model: 99 turbo
Mmmm , that’s interesting . If I pull fuse 9 then there is no draw and meter reads Zero so something that was drawing is not at the moment . Clock is not the problem then .
Battery problem possibly , what should I see fully charged 13.5 v ?


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PostPosted: Fri Sep 20, 2019 12:54 pm 
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Joined: Wed Feb 24, 2010 4:31 pm
Posts: 84
Location: Ireland
Car Model: '91 900 S ,1984 900 GLE
Hi Roy
Don't know if you have had any joy yet.
Alternator faults can also sometimes put a continuous draw on a battery of a few amps.
Was the ignition key out and the door closed when you did your drain test ?
No hidden car alarm or anything like that fitted?
You should get 13.5 or 13.8 volts approx.
Paul


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PostPosted: Fri Sep 20, 2019 4:46 pm 
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Joined: Sat Jun 20, 2009 4:36 pm
Posts: 117
Car Model: 1978 99T 3 door, black
I have just been and checked.
My 99T pulls between 15 and 20mA - the value does not settle, That is powering clock and a small LED on the radio (plus whatever else is going on inside the radio).
Battery voltage is 12.5 I get about 14V at the cigarette lighter socket when the engine is running at 2000rpm and no extra electrical loads (lights, heater, rear de-mister)
As my 99T lives in my house I disconnect the battery as soon as I park up, I charge the battery every 3 months or so.
Your new battery may not have come fully charged depending on how long it sat around in the store. If you have only driven short distances it might not have had time to get to fully charged.

This from Quora:

Quote:
Today most car batteries are sealed, and come more or less fully charged. Moreover, the charging circuits in modern cars are much better at avoiding excessive charging voltage. So unless you have an old car (at least forty years old) you have no need at all to worry about charging a new battery. Just put it in your car and go, making sure you clean the terminals thoroughly before connecting them. And check the charging voltage with the new battery and the engine running: it should be about 14 volts. If the charging voltage is much lower, the problem is most likely the car, not the battery; if it is much higher, the car has a problem which killed the old battery, and will probably soon kill the new one.


https://www.quora.com/How-should-I-char ... ar-battery

"How long would 23 MA take to flatten a battery ?" - instantly
"How long would 23 mA take to flatten a battery ?" - weeks to months


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