Conference unifix::sailing

    for 12.5 amps Id use at least #12 awg, better would be to use #10.
    Dont let someone confuse this with noting that household wiring
    allows 15 amps for #14 wire. The problem is IR drop, and with only
    12 volts to start with not as much loss is tolerable here as with
    120 volts.

The light output from a light bulb varies as the fourth power of the 
voltage, so if the voltage drop in your wiring is 5% (0.63 volts for a 
12.6 volt battery, the light output will decrease to 81% of the light 
output with no voltage drop. (Note: This implies that large wiring 
should be used for navigation lights, especially masthead lights, to 
ensure maximum brightness of the lights). See any standard electrical 
engineering reference book for the resistance of various gauge wires.
Bulb life decreases rapidly with increasing voltage, so there is a 
tradeoff (isn't there always?).

By the way, I find the back scattered light from a handheld searchlight 
makes seeing anything with the searchlight very, very difficult. The 
narrow searchlight beam doesn't help, either. I've used my seachlight 
once in 12 years (and didn't really need it then). 

Alan

    Ohm's law   R=  E/I.  So maximum resistance is .5/13 = 0.0385 ohms.
    Wire length is 60 feet. (30 feet to lamp and 30 feet back, or .25
    volts in each leg).
    
    Wire tables are usually ohms per thousand feet, so (1000/60)*0.0385
    = 0.6410 ohms per 1000 ft.
    
    for reference
    
    gauge          ohms/1000 ft
    
    6			.395
    
    8			.628
    
    10			.999
    
    12			1.59
    
    14			2.53
    
    16			4.02
    
    all above for annealed copper.
    
    It seems it always takes 2 sizes (gauges are usually only even)
    bigger than you think!
    

	I am planning to move the location of my batteries to a point 
further from my motor. They will be approximately 15 feet distant.
My motor draws 190 amps while starting so it looks like I'll need 2/0 
wire for the installation. In looking through my marine supply catalogues 
I don't find much available in that size and what is available is pricey;
up to $6.00/foot.
	I found some welding cable in a Northern Hydraulics catalogue for
about $2.00/foot but I can't get much descriptive information on it. I 
called customer service and they had no more info than the catalogue. They 
suggested I order it and return it if it isn't satisfactory. Before I do 
that I thought I'd ask for opinions in here.
	My main concern is with the insulation, which is called "Excelene". 
I doubt if the wire is Aluminum but if it is I'll just send it back. The 
cable will be laying in oily salt water at least part of the time. I imagine 
virtually any insulation will be impervious to water but how about the oil, 
salt etc.
	Anyone have any advice?

Paul
    
    P.S. This is also posted in the Powerboats conference.

re -.1:

Advice? Sure. I'd use only USCG approved cable. Jamestown Distributors 
(800-423-0030) has 2/0 cable in 25' and 50' lengths for less than $3 per
foot (1991 price). 

Use high quality terminals. I remember seeing some in the Ample Power 
catalog (I think it was). These were screwed together compression
fittings, not crimped fittings. Maybe $10 to $15 each. 

Be sure you secure the cable with heavy duty cable clamps every foot or
so. Chafing through the insulation could have dramatic results. Consider
using a fuse at the battery. Ample Power has them (I think) in ratings
up to 500A or so. 

    Do you have the number/address for Ample Power?

    re -1> No, I don't have a number or address for Ample Power. Could
    someone post it?
    
    Thanks for the quick replies. I'll call Jamestown tonight.
    
    Paul

Ample Power:  technical information 206-789-4743
              orders                800-541-7789

battery cable compression connectors  $7.99
2/0 tinned cable                      $4.99/foot
300A fuse                            $42.00 (other ratings available)

Prices may be lower from dealers (eg Jack Rabbit Marine, 914-834-3985)

    Thanks Alan. It looks like the two gel cell batteries are going to be
    the cheapest part of this project.  ;^)
    
    Paul