T&T: A Shunt Question

[Peter Bennett]

Saturday, October 27, 2007, 11:26:41 AM, Thomas wrote:

TA> The prior owner of our boat has devised a rather complicated system of
TA> solenoids to tie battery banks together when oil pressure turns the solenoids
TA> on or when a manual switch is engaged.  It has worked for three years so far
TA> without fail.  However, it involves the use of a "Shunt" which I do not
TA> understand.  Can you explain what this electrical circuit is doing and why it
TA> is there?  It seems the system would work without the shunt.  It appears to be
TA> involved in breaking both the + and - side of the busses.

A shunt is a precision low-value resistor that is inserted in a
circuit to provide a means to measure current in the circuit.  Shunts
are typically designed to produce 50 mV at rated current, and are used
with a voltmeter that reads full scale for 50 mV, but is labelled to
suit the rated current of the shunt.

The Link 10 and similar battery monitors use shunts in the negative
battery leads to measure battery current.

Each shunt should have two large terminals for the circuit being
measured, and two smaller terminals to feed the meter.  The wires to
the meter can be quite small - #22 might be typical.

-- 
Peter Bennett, VE7CEI    Vancouver, B.C., Canada
Ennos 31 "Honeycomb"
GPS and NMEA info: http://vancouver-webpages.com/peter 
Vancouver Power Squadron: http://vancouver.powersquadron.ca