There are four basic units of measurement for electricity:
Power: measured in Watts
Current: measured in Amps
Voltage: measured in Volts
Resistance: measured in Ohms
You can have proper voltage but reduced current and power. For proper operation you need Power, Current and Voltage with minimum resitance.
Excellent Read on Choosing Proper Wire: http://www.rowand.net/Shop/Tec...t.htm
1) Always run direct to the battery (humminbird Recommended). Utilizing existing boat wiring harness can underpower the electronics. Not all boats are wired the same and wire gauge, connections and circuit protection may limit proper current flow to the unit.
2) If you need to extend the wire use smaller gauge wire (Bigger thickness) for the longer you need to extend. 18 Gauge is minimum gauge but I prefer 14-16 gauge to provide ample capacity for years of trouble free service.
Check out this Voltage Drop Calculator: http://www.altronix.com/app_notes/calc.php
Choosing 14ga over 18 ga in a 20' Span reduces voltage drop approximately 2/3rds. That is why wire size and resistance free, corrosion free wire is important.
3) A 3 Amp Fuse is recommended. I prefer Blade Type Automotive Fuses over Glass Bulb Fuses as they don't lose contact as easy. THe Spring Loaded Fuse Holders in Glass Bulb Fuses can disconnect in rough water shutting down the flow of electricity to the unit.
Blade Style Fuse:
Blade Style Fuse Holder: (Available at Auto Parts Stores):
4) All connections should be soldered. Using Butt Connector Splices is asking for trouble down the road. Easier for corrosion to enter connection. Improper splice can reduce electrical flow. Connections can vibrate and loosen wires in connector. Or Over crimping can damage wires. Solder Connection creates a better connection. All Connections should be heat shrink to reduce cane of corrosion from water or mositure intrusion.
Video How to Solder: http://youtu.be/6QznAAwL8rI
Video How to Heat Shrink: http://youtu.be/d-j98tkAbh8
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Battery Voltage and State of Charge:
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