Probably won’t have any problems with a 60A alternator conversion and wires
IF all connections are tight.
American Nearest Ohms Max Max
Wire British per Current Current
Gauge SWG Foot (single)* (bundles)**
#10 #12 .001018 55 33
#12 #14 .001619 41 23
#14 #16 .002575 32 17
* Continuous Duty current, single wire in open air.
** Continuous Duty current, wires or cables in conduits or bundles.
Both of the above assume maximum wire temperature of 212F and maximum
ambient temperature of 135F. (source - ARRL Handbood copper wire table.)
Of course, the above is for continuous duty - for the short time that it
takes to get the battery back to near 13.75 volts, 60 amps is probably no
problem.
However, a loose joint will be fatal. (1 volt drop at 60 amps = 60 watts of
heat in a small area!)
I have no idea what the internal resistance of an ammeter is, but it will be
very low and you should be able to put a few feet of wire directly across
its leads to share the current and see what the meter does. With enough
wire, it should make the meter read approximately half sensitivity and keep
it from burying itself on startup. If you can measure the voltage drop
across the meter when charging (or discharging) at a given current, you can
easily calculate the required resistance shunt to change it from 30A to 60A
for example.
#12 wire (AWG) (approximately #14 British SWG) = .001619 ohms/foot,
therefore by ohms law (Volts = Current X Resistance) at 60 Amps you would
get about 0.1 Volt per foot drop. If you had more than seven feet of wire
going from the alternator through the rest of the circuits to the battery, a
diode in the line would help take some of the load exceeding 60A, if it had
big enough wire and a heatsink (watts = 0.7 times excess current through
it.) I suppose you could add some extra resistance (total of about 14.5
feet of #12 wire) so that with a power diode going directly to your battery
the ammeter never saw more than 30 amps to keep the ammeter from being
pegged.
Could also try a BIG Shottkey diode (has less forward voltage drop.)
Don’t hold me to this - haven’t really thought if the regulator would
interfere or not. Probably somebody here has already been through all of
this.
Frank (aka WB6UNH)
‘59 TR3 (with stock generator)
|