alternator cables

[dan]

hello people..
  i am currently refitting my 0-200 w/ a 55 amp alternator, can anyone assist or give me advice on what gauge  cable to use?
  also is there a battery requirement or can i use my old 30 amp one?...
                                                         appreciate all the info//

[Waiter]

Dan,

Is that an automotive alternator with a remote sense line? The remote sense allows you to use a smaller guage wire.  I'm using a #10 wire for 50 amps. The Remote sense adjusts the alternator output voltage so that the voltage is correct at the battery, not at the alternator terminals. This can carrect for a substantial voltage loose in the wire.

A #8 should do the trick, even if you don't have remote sense.

Waiter

[dan]

hi waiter,
  somehow i knew i could count on you....anyway what do you mean by remote sense line?....
   the schematics i got ..was the Main cable goes straight to the batt..
   the back has a plug w/ 3 wires one is a  "DUMMY" then there is a "energizing" line ( from the back) to be connected to a switch like an ignition...  also where do you recomennd i place the 55 amp..circuit breaker?.. :wink:  :wink:  thnx

[dan]

and yes one more thing>>>
   #8 cable means...8 gauge?..

[Drew]

Dan,
Take a look at aeroelectric.com for schematics.  You will want the big breaker on the "big line" coming off the alternator.  The small powerline goes to your main bus via a breaker.  The alternator needs power to make power

[Anonymous]

Remote Sense is very common with Japanese manufactures, i.e. Toyota, Nissan.  The Internal regulator of the Alternator needs to "measure" what the output voltage is, in order to maintain the correct output for charging. Kind of like you taking your digital voltmeter, measuring the voltage, then adjusting the alternator output to maintain that voltage.

Most alternators (American) just measure (sense) the voltage at the alternator output, very easy, no additional parts.

In remote sense, The Alternator has a terminal called "SENSE".  A small wire is run directly to the battery, from the alternator. No current flows in this wire, so it can be very small (22 gauge). The purpose of this wire, is to report back to the Alternator, what the voltage is at the Battery, then the regulator inside the alternator adjusts its output to maintain the correct voltage at the battery, NOT at the alternator output terminal


OK, so why the big deal?

If you run smaller size battery cables, a long distance (does this sound familiar) there is going to be a voltage drop in the cable. If I run a size  14 cable, and try and pump 50 amps through it, the cable itself will drop almost 2 volts.  If the alternator is putting out 14.6 volts, the battery will only see 12.6 volts, not enough to charge the battery.

Now, with remote sense, The alternator will see that the battery only has 12.6 volts on it, so it will raise the alternator voltage output until it sees 14.6 volts at the battery. If you took a voltmeter, you would measure 14.6 at the battery, and 16.6 volts at the alternator.

Running 8 guage wire 15 feet, you will have approximately 1/2 volt loss in the cable at 50 amps.  Unless your EZ is "Full Electric" (mine is, hydraulic pump, electric everything) you will probably only see the full 50 amps immediately after engine start, then only for a very brief time of several seconds. It will taper off fast as the battery accepts the initial recharge.

A #10 wire may work OK, but I wouldn't go much smaller than this if your alternator doesn't have a remote sense line.


Take a look at this site for a really neat wire loss calculator

http://www.stealth316.com/2-wire-resistance.htm

Waiter