Alternator Sense Wire ?

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Dale4407

.
May 19, 2004
45
C-C 34 Jax
Has anyone heard of installing a resistor or a diode in the sense wire from the alternator/regulator? It seems that I read here a long time ago that it would cause the regulator to sense a lower charge in the batteries and continue to charge at a higher rate for a longer period. If that is the case, probably not a problem for the day sail while just motoring to and from the dock, but for extended motoring would it not cook the batteries? I've got a heat shrinked lump in the sense wire which I suspect is just that and am wondering if there is a down side to having it. I was surprised that a first rate alternator shop here locally really didn't have much thought about it. Any speculation would be appreciated.
 
D

Dale4407

.
May 19, 2004
45
C-C 34 Jax
Has anyone heard of installing a resistor or a diode in the sense wire from the alternator/regulator? It seems that I read here a long time ago that it would cause the regulator to sense a lower charge in the batteries and continue to charge at a higher rate for a longer period. If that is the case, probably not a problem for the day sail while just motoring to and from the dock, but for extended motoring would it not cook the batteries? I've got a heat shrinked lump in the sense wire which I suspect is just that and am wondering if there is a down side to having it. I was surprised that a first rate alternator shop here locally really didn't have much thought about it. Any speculation would be appreciated.
 
G

Gord May

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Jun 4, 2004
629
Sailboat - 48N x 89W
Diode in Alt' Sense

Dale: You are exactly correct in your understanding I’ve used as diode to fool the alternator regulator, but with a DPDT switch to select either diode in sense (series), or short out diode for direct sense. NOTE: Unless the switch is Make Before Break type, do NOT switch while alternator turning. The diode reduces the sensed voltage by about 0.7V, fooling the alternator into a higher output. This is both it’s utility, and it’s inherent danger. I wouldn’t do it again. (too little gain, for too little potential pain). Gord
 
G

Gord May

.
Jun 4, 2004
629
Sailboat - 48N x 89W
Diode in Alt' Sense

Dale: You are exactly correct in your understanding I’ve used as diode to fool the alternator regulator, but with a DPDT switch to select either diode in sense (series), or short out diode for direct sense. NOTE: Unless the switch is Make Before Break type, do NOT switch while alternator turning. The diode reduces the sensed voltage by about 0.7V, fooling the alternator into a higher output. This is both it’s utility, and it’s inherent danger. I wouldn’t do it again. (too little gain, for too little potential pain). Gord
 
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