> Just a note on the alternator conversion. I put in a pair of modern
> headlights in my 3. They are extremely bright at idle and the dash light
> stays off, indicating adequate charging. My generator is an NOS one and puts
> out the specified charge. My NOS regulator needed to be adjusted. Just
> curious if your gen and reg are performing properly.
I went through this many years ago ... the stock TR3A generator was rated at 19
amps (although most cars will have the later 21 amp unit). I measured the total
load, driving in the winter with the headlights, heater & wipers on; at 24 amps
!
With a properly adjusted regulator, this can be seen in the ammeter ... it
should show a very slight discharge under these conditions. If it is set "hot"
enough to still charge with everything on, it will overcharge with everything
off (reducing the life of the battery); plus there is a very real chance it is
allowing the generator to output too much current, which will eventually
overheat and damage the generator.
But even if I mis-measured and the load is less than that, the
generator/alternator still has to put back whatever drain it took to start the
car, before you get to your destination. In cold weather, this can be a
considerable chore.
Batteries are kind of odd devices, not very efficient and their efficiency
depends a lot on the charge/discharge rate. But say for the sake of argument
that it takes 60 amp-hours to fully charge a healthy battery from empty.
Further suppose it will start the car 10 times (again we're talking cold weather
here). So probably it takes something on the order of 6 amp hours to put back a
single start. If you only drive the car 15 minutes after starting it (which was
about my commute to work in those days), that means the generator must put 24
amps into the battery (as well as powering whatever devices are turned on).
Obviously, a 21 amp generator just isn't going to cut it !
Randall
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