High voltage

[jhodge]

Does the original Merc rectifier have a regulator in it? I replaced the original with a radio shack item and after installing a voltmeter I read high voltages. The newly installed voltmeter is fairly accurate and agrees with a digital meter reading voltages at the battery. What happens is that when the engine is started the voltages read in the 12 to 13 volt range and gradually creap up to around 17 volts. I am ssuming this is happening because the battery is reaching full charge and builds resistance to any more charge. The manual says the stator puts out 7 to 9 amps and it is feasable to install a switable load to use up some of this excess when the battery becomes charged. This all happens at idle rpm and doesn't vary much at higher rpms. Is this high voltage condition harmful to the engine electronics or the fish depth finder or the tach? If I can regulate the voltage, is 14 volts about the right amount for max voltage? Engine is 1986 60 hp 3 cyl merc SN 931265. Thanks JH

 

[Chris1956]

Re: High voltage

The parts list for you motor shows a standard Merc Rectifier. It is identical to the Radio Shack rectifier, except the RS rectifier is more durable.

Normally the extra charging the motor does is of little consequence. It is a 9Amp(at WOT) or so charger, which is nothing compared to a 100Amp/hour battery. if your FF does not complain, I would not worry about it. If it does complain, you may want to dig up an aftermarket VR or maybe some voltage cutout device like a zener diode.

 

[j_martin]

Re: High voltage

The 9 amp system relies on a battery in good shape to control the voltage. It will supply 9 amps at up to about 90 volts at WOT. The battery holds it down.

That will cause the battery to use water, and if it's not regularly maintained, will wreck the battery. If you keep the water up, it doesn't seem to shorten battery life significantly.

So, if the voltage is too high, check the battery.

hope it helps
John

 

[jhodge]

Re: High voltage

Thanks for replying. Its a relief to know that the old rectifier was not also a regulator. The battery is relatively new and holds a good charge, being a deep cycle type. I do disconnect the negative pole when ever not in use. I supposed the 17+ volts won't hurt anything, but it makes me uncomfortable and am trying to figure out some Rub Goldberg device that makes Gold out of the extra power. So far I've only come up with a sealed beam headlight with the high and low beam settings for variable resistance. I went to radio shack and checked on their rheostats, but only had low capacity ones. I am not familiar with zenair resitors but guess i could google some information to see what would work. One problem with this setup is if I forget, then the battery gets used up and I'm really in trouble. Any other suggestions? Thanks again. JH