> Chuck wrote: > >> A lot of solid-state equipment such as GPS receivers may not draw much >> power in normal operation. But, at initial power-up it can draw >> substantial surges. This is called "In-Rush Surge." It's caused >> primarily by charging the device's main capacitors. It's become more of >> a problem in recent years as capacitors have improved and have lower >> internal series resistances. Many modern electronic devices have >> switch-mode power converters internally to convert the nominally 13.5V >> input to 5V or 3.3V for use by the internal logic. These switch-mode >> converters are operating at higher and higher frequencies these days >> which requires input capacitors with lower and lower internal >> resistances. >> <<SNIP>> >> >> The solutions possible are: Bigger wire. Even though your GPS receiver >> only draws 500mA when operating, you might want to size the wire for the >> 10A in-rush surge that it may draw. The other option is a capacitor >> placed near the receiver. 10,000mFds at 35V, for example, placed near >> the receiver would dramatically reduce the amount of in-rush surge seen >> by the boat's electrical system. >> >> Chuck >> >> >> > > > Capt. Mike Maurice > Tualatin(Portland), Oregon. Be careful with very large capacitors in a circuit. If you should happen to contact the two terminals you can get a very large shock from it. I think an inductor in series with the input lines would be safer at limiting input current rush over capacitors as capacitors tend to stop a sudden change in voltage while inductors stop a sudden change in current. They also tend to reduce electrical noise in the line from other devices if I remember correctly. I graduated as an electrical engineer 35 years ago but it has been a long time since I did any work in the field. Robert Wightman Midnight Sun va3ilw@rac.ca