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That's a significant drain, even with alarm, radio and clock it should =
last for 2-3 weeks.
Your battery voltage off-car seems OK, but that is not a good indication =
of the amount of charge i.e. cranking power. If you put it back on the =
car after three days and it cranked OK that does indicate the battery =
itself is OK - up to a point.
However the Lucas Fault Diagnosis Manual states that if a battery =
becomes 25% discharged then the on-board charging systems will never get =
it back to full capacity, and if it has become completely discharged =
they will never put back more than 50% capacity. For that reason a =
flattened battery has to be boost charged for a period to restore full =
capacity. Using a conventional charger this means charging at 16-17v =
for a couple of hours in a well ventilated space. Or you can use one of =
the more sophisticated 'maintenance' chargers but only if they have a =
'recovery' program, and not all do. These charge using pulses of up to =
20v.
But back to the drain. If you have an analogue meter switch to its 12v =
i.e. VOLTS range and connect it in place of the battery earth lead. =
With no drains on a car with an alternator you should see a few volts =
registered. If it shows 12v there is a drain. In that case the first =
thing to do is unplug the alternator, and if the drain drops to zero =
that is the culprit. With the few volts registered unplugging the =
alternator should also drop it to zero. But if still at 12v start =
disconnecting things like your radio, the purple circuit fuse, remove =
browns from things like the ignition switch, lighting switch, starter =
relay, hazard fuse and so on, looking at the meter each time. If still =
there remove the browns from the starter solenoid, and finally the =
battery cable from the solenoid, but normally it will have been =
discovered by now.
You can also do this with a digital meter but they are far more =
sensitive and will show 12v even with just the normal alternator =
leakage, and may not fully drop to zero with that disconnected if there =
is dampness anywhere.
PaulH.
----- Original Message -----=20
After leaving my MGB GT V8 for a few days - maybe 4 or 5 I find the =
battery is completely flat. Did that 3 times. So I took the battery =
out, charged it and waited 3 days. The voltage dropped from 13.15V on =
Sunday 3pm to 12.91V 3pm Wednesday which does not seem to indicate that =
it is the battery's problem?
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Content-Transfer-Encoding: quoted-printable
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<HTML><HEAD>
<META content=3D"text/html; charset=3DUTF-8" http-equiv=3Dcontent-type>
<META name=3DGENERATOR content=3D"MSHTML 8.00.6001.23588">
<STYLE></STYLE>
</HEAD>
<BODY bgColor=3D#ffffff text=3D#000000>
<DIV><FONT size=3D2>That's a significant drain, even with alarm, radio =
and clock=20
it should last for 2-3 weeks.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Your battery voltage off-car seems OK, but that is =
not a good=20
indication of the amount of charge i.e. cranking power. If you put =
it back=20
on the car after three days and it cranked OK that does indicate the =
battery=20
itself is OK - up to a point.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>However the Lucas Fault Diagnosis Manual states that =
if a=20
battery becomes 25% discharged then the on-board charging systems will =
never get=20
it back to full capacity, and if it has become completely discharged =
they will=20
never put back more than 50% capacity. For that reason a flattened =
battery=20
has to be boost charged for a period to restore full capacity. =
Using a=20
conventional charger this means charging at 16-17v for a couple of hours =
in a=20
well ventilated space. Or you can use one of the more =
sophisticated=20
'maintenance' chargers but only if they have a 'recovery' program, and =
not all=20
do. These charge using pulses of up to 20v.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>But back to the drain. If you have an analogue =
meter=20
switch to its 12v i.e. VOLTS range and connect it in place of the =
battery earth=20
lead. With no drains on a car with an alternator you should see a =
few=20
volts registered. If it shows 12v there is a drain. In that =
case the=20
first thing to do is unplug the alternator, and if the drain drops to =
zero that=20
is the culprit. With the few volts registered unplugging the =
alternator=20
should also drop it to zero. But if still at 12v </FONT><FONT =
size=3D2>start disconnecting things like your radio, the purple circuit =
fuse,=20
remove browns from things like the ignition switch, lighting switch, =
starter=20
relay, hazard fuse and so on, looking at the meter each time. If =
still=20
there remove the browns from the starter solenoid, and finally the =
battery cable=20
from the solenoid, but normally it will have been discovered by=20
now.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>You can also do this with a digital meter but they =
are far=20
more sensitive and will show 12v even with just the normal alternator =
leakage,=20
and may not fully drop to zero with that disconnected if there is =
dampness=20
anywhere.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>PaulH.</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- =
</DIV><FONT=20
size=3D-1><FONT face=3DArial><BR>After leaving my MGB GT V8 for a few =
days - maybe=20
4 or 5 I find the battery is completely flat. Did that 3=20
times. So I took the battery out, charged it and waited 3 =
days. =20
The voltage dropped from 13.15V on Sunday 3pm to 12.91V 3pm Wednesday =
which=20
does not seem to indicate that it is the battery's=20
problem?</FONT></FONT></BLOCKQUOTE></BODY></HTML>
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