Hi Ron,
> #4 welding cable is different in diameter (larger) than solid copper
> single strand. Circular mils of copper is usually close. That said some
> tefzel #4 that looks close to same strands are different diameter, so
> don't think diameter is absolute.
As far as I have been able to find on the internet, gauge indicates
diameter, irrespective of the material. But anyway...
> "I also have that Ducati-thing on the other alternator. Guess I have to
>> put a diode in series with its sense lead to crank up the voltage
>> somewhat."
>
> Good idea to increase setpoint if you can. Where exactly would you put
> diode in circuit? What value diode?
Most regulators have multiple 12 Volt connection points. So does the
Ducati regulator. One of these 12 Volt points (the one labeled 'C') has
the sole purpose of measuring the voltage. You can connect this directly
to the adjacent connector (B, or R, which carries the actual output) as
is often done, so it measures its own output, but a more correct way is
to connect it directly to the battery, so that any voltage drop over the
feeder cable is corrected. Suppose you want to have a voltage over the
battery of 13.7 Volts, and the cables have a loss of 0.5 Volt, then
connected in this way the regulator will crank up the voltage until it
sees 13.7 Volts at the battery, i.e. it will output 14.2 Volts to
correct the voltage drop over the main cable. Ok, I guess almost nobody
does this as most people don't know about it. BTW, The regulator for the
SD20S alternator has a similar option.
You can however do more with this if you are creative. A standard diode,
like a 1N400x, has a forward voltage drop of about 0.6 / 0.7 Volts. So,
if you put this diode in series with the wire connected to the C, the
regulator will see 0.7 Volts less than the actual voltage. It will
therefor output more to correct for this condition. With other words,
the output will increase with 0.7 Volts.
The diode will not carry any significant current, any rating will
suffice. You could put multiple diodes in series if you want to have a
multiple of 0.7 Volts. A Skottky diode has a forward drop of about 0.2
Volts. You can also use a resistor divider to increase the output with
any value, but keep in mind that a resistor also divides the voltage
fluctuations while a diode is absolute, so using a resistor divider is
somewhat less stable. Another trick is to use a temperature sensitive
resistor, so the regulator will adjust the voltage according to the
temperature, something that is highly appreciated by the battery.
--
Frans Veldman
|