Windy Nation 100 AMP DC Watt Meter - Manual (Page 9)

Watt Meter User Manual
Revision 1.0
Doubling the current increases the heat produced four times, so at 75 Amps, approximately 28 Watts of heat
is produced – mostly in the Meter’s wires.
The high current handing capabilities will be maximized when the meter's SOURCE and LOAD wires are
kept short and cool. Cut the wires as short as is convenient for high current operation. A fan blowing over the
wires will help their cooling. At moderate currents there is little heating. Using a "three-wire" connection will
also lower heat generation.
5.2 I NDUCTIVE L OADS
Loose connections and long wires on circuits switching high currents can damage electrical components.
The problems can be largely eliminated by ensuring that connections are secure/not intermittent (e.g. not just
twisted together) and to a lesser degree by keeping wire lengths short and by twisting wire pairs together to
reduce their inductance.
Wires exhibit a property called inductance. Inductance is an indication of the amount of energy stored in a
wire's magnetic field due to the flow of current.
If you interrupt the current flow, say with a switch or pulling apart a connector, the magnetic field collapses
and induces a voltage in the wire to try and oppose the drop in current. Depending on the specifics of the
wire, current and materials near the wire (like iron) the induced voltage can be quite high. In fact, it can give
you a mild shock and damage electrical components still connected to the wire by generating voltages that
exceed their ratings. This is one of the reasons capacitors and diodes are needed on brushed motors in
addition to reducing RF noise.
Always disconnect the meter from the highest inductance wiring first.
5.3 B ATTERY C HARACTERIZATION
5.3.1 Battery Charging
You can monitor the current, accumulated charge and energy into and voltage on a charging battery.
Connect the meter as shown in Section 3.1.1. Be sure the battery is not connected before the source
generator is turned on, as the meter will track the minimum voltage on the battery during the charging
process. With the source on and the battery charging, the meter displays the ongoing charging electrical
values. The current (As) and power (W) show the average rate of charge and the voltage indicates the
current battery charging voltage.
CAUTION: When charging a battery, do not operate it outside its manufacturer's specifications. Do not allow
the battery voltage to exceed the maximum value specified or charge at a current that exceeds the maximum
specified.
5.3.2 Battery Discharging
When discharging a battery pack through the meter into a load you can monitor key battery parameters like
actual available charge and energy, peak and average current and battery voltage.
Connect the meter as follows:
The diversion load device you connect on the LOAD side must be capable of handling the discharge power
the battery pack can provide. Example loads include, light bulbs, power resistors, and devices specifically
designed to discharge a battery like some chargers in discharge mode.
If the battery pack voltage at the end of discharge will be less than the minimum 4.0 V the meter requires a
battery of at least 4.0 V to the 3-pin auxiliary power connection.
Page 9 of 11 Windy Nation 04/19/2012