Joseph,
A fully charged battery is 2.12v per cell. 6 cells = 12.72 volts.
Now there is a small amount of resistance in each cell so it requires at least
13.92 volts to fully charge a 12 volt battery. (measured at the battery)
Your reading of 12.75 volts indicates that your alternator or regulator is a
dead player.
How far can you last without an alternator?? One of the ratings for batteries
is reserve capacity. This is the length of time that a fully charged battery
can deliver 25 amps at 80 degrees F and still have 10.5 V left.
So if you look at the top of your battery and it says 90 minutes that is how
long you can run at a 25 amp discharge. Now your car probably doesn't draw 25
amps when running with the lights off, so if it draws 10 amps multiply by 2.5.
Also if you are willing to run the battery complety flat that will give you
more time. (If you have electronic ignition not much longer, most electronic
systems quit and go home at somewhere between 9-10V)
bottom line get the alternator fixed and motor on.
Rick Ewald
also a 67 MGB
Thanks for all the quick responses to my stupid oil change question. I
double checked the oil level and it's just slightly over max and the
bubbles have disappeared. So I assume there isn't a problem. To answer
some of the questions out there: I replaced the original multi-piece
filter with a spin on filter adapter. The opening of the filter faces up
(I'm not sure if that's inverted or not). And I've always filled the
filter before putting it on. (I don't know where I picked it up. But it
can't hurt.) Now the alternator question:
I apologize for not paying attention to the recent alternator thread.
Since I had a new Bosch alternator fitted about 2 months ago, I didn't
think I had to. Back then, the ignition light wouldn't go on. Now it
won't go off. I checked the belt and it seems to be okay. Then hooked up
the multi-meter, and even with the engine revving, the voltage still
hovers around 12.75 volts. Shouldn't that sucker be pumping out at least
14? I noticed that the regulator on the back of the unit is a Lucas,
which means it's probably the old one. Am I in for a new regulator or
does the whole thing have to go? And can I drive it for a couple of days
without fear of running out of juice on the road? (That's the stupid
question I was promising you.) Thanks in advance.
Joseph
67 B Roadster
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