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Old 12th November 2019, 05:09   #1
ardvark
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Default Flat Battery Anomaly

Yesterday morning when going to work the car unusually had a flat battery. The AA man came out and tested the battery,alternator and the way the system powered down when the car is locked. Everything apart from the flat battery was fine. He charged the battery for about 10 minutes and off he went. I went to work, travel time about 40 minutes and home time the car started as though nothing was wrong. This morning I checked the car it started no problem.
Has any members had the same problem?
Any idea what happened?
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Old 12th November 2019, 09:07   #2
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Your battery's level of charge was too low on a cold November morning. You need to buy or borrow a mains powered smart charger and charge your battery for at least 24 hours, preferably longer, to restore it to fully charged. If you don't, not only will you risk a repeat performance but your battery will ultimately fail permanently causing more inconvenience and expense.

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Old 12th November 2019, 18:51   #3
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So do it NOW.--------
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Old 13th November 2019, 12:28   #4
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Do you have a fuel burning heater? If so it may be faulty and coming on when it shouldn't.

If the problem returns try unplugging the FBH and see if things improve.
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Old 14th November 2019, 18:13   #5
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Quote:
Originally Posted by Mike Noc View Post
Do you have a fuel burning heater? If so it may be faulty and coming on when it shouldn't.

If the problem returns try unplugging the FBH and see if things improve.
I believe when disconnecting the FBH, one MUST disconnect the multipole control connector BEFORE disconnecting the power connector (or it's associated fuse F8 in the engine fuse box), otherwise the FBH will be permanently damaged.

Likewise when reconnecting, one MUST reconnect the power connector BEFORE the multipole control connector.

I stand corrected if I am wrong.

Last edited by MarkS; 14th November 2019 at 18:18..
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Old 8th March 2020, 11:45   #6
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Guess what happened this morning?
You guessed it.
Flat as a NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-.
This business of the alternator diode playing up.
How can I check this?
There is no light on the dash saying the battery is not charging.
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Old 8th March 2020, 12:18   #7
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Quote:
Originally Posted by ardvark View Post
Guess what happened this morning?
You guessed it.
Flat as a NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-NAUGHTY WORD-.
This business of the alternator diode playing up.
How can I check this?
There is no light on the dash saying the battery is not charging.
Define flat - no headlights on bright? I ask because after months after checking /charging batteries, monitoring the OBD charge, my son-in-law's car just refused to start even with a fresh battery. Previously a freshly charged battery always got it started, but yesterday (thankfully) I heard the tell-tale solenoid click. Out with the starter in with a spare and burst into life on the same battery. Should have realised this sooner but the starting with extra juice always helped, solenoid kit now ordered as the spare starter was from a 1999 car.

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Old 8th March 2020, 12:19   #8
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Start the car and check the voltage at the battery with a voltmeter, it should be over 13.5volts and when you switch it off drop down to 12.5 ish. If it stays at mid 12s while running its not charging at all and if it does not get to 13.5 or more its only partially charging, anything more than 14.5v and you will fry the battery.
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Old 8th March 2020, 13:37   #9
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I get the impression that your battery is on its last legs.--How old is it ?

If you start with your battery flat and put it on one of those chargers that light up green to tell you your battery is charged.

1/ If it takes all night before it lights up green then your battery is probably OK.

2/ If it lights up after only an hour or two your battery is on its last gasp and needs changing.


Let us know what voltage you are getting at the battery terminals with your engine ticking over.
This is an alternator output check.

Normally with a charged battery around the 14 volt mark.

Can be as low as 13.5 volts or as high as 15 volts.

Batteries like to work at around bath water temperature.

Much higher than that and you'll start to lose water from the electrolyte.---



More info in the ---really, really useful info section on the main forum page.


Look for my posts.
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Old 11th March 2020, 10:13   #10
SD1too
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Quote:
Originally Posted by SD1too View Post
... You need to buy or borrow a mains powered smart charger and charge your battery for at least 24 hours, preferably longer, to restore it to fully charged.
Hello Al,

I offered you this advice four months ago. Did you follow it? If so, what was the result?

Quote:
Originally Posted by ardvark View Post
This business of the alternator diode playing up.
How can I check this?
There is no light on the dash saying the battery is not charging.
You are looking for a complicated answer to a simple problem Al.
  1. Look at the basics first and proceed logically.
  2. Don't make any assumptions.
  3. Measure things and record the results.

Simon
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