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View Full Version : New rectifier and still overcharging !


keeper
07-10-2009, 07:45 PM
HI GUYS !

I REPLACED THE RECTIFIER ON MY 1977 MERCURY 1750 (175 HP) BECAUSE MY BATTERY GAUGE WAS HITTING 16 VOLTS. I THOUGHT IT WAS A RECTIFIER / REGULATOR. WELL AFTER REPLACING IT, IT IS STILL OVERCHARGING. ITS ONLY ABOUT 13 AT IDLE, BUT WHEN YOU STEP ON IT, IT PEGS OUT. WHAT GIVES ? I BELIEVE IT IS THE 9 AMP SYSTEM.
ANY HELP WOULD BE GREATLY APPRECIATED.

THANKS

MARK:nonod:
j_martin
07-10-2009, 07:51 PM
HI GUYS !

I REPLACED THE RECTIFIER ON MY 1977 MERCURY 1750 (175 HP) BECAUSE MY BATTERY GAUGE WAS HITTING 16 VOLTS. I THOUGHT IT WAS A RECTIFIER / REGULATOR. WELL AFTER REPLACING IT, IT IS STILL OVERCHARGING. ITS ONLY ABOUT 13 AT IDLE, BUT WHEN YOU STEP ON IT, IT PEGS OUT. WHAT GIVES ? I BELIEVE IT IS THE 9 AMP SYSTEM.
ANY HELP WOULD BE GREATLY APPRECIATED.

THANKS

MARK:nonod:

So just why would you believe a bad rectifier would cause overcharging?

The full output of the system goes to the battery all the time. It is not regulated. Whatever your instruments and accessories don't use is absorbed by the battery. After it hits full charge, the excess current hydrolyzes the water in the electrolyte. That action "regulates" the voltage.

If you do not maintain your battery religeously, the electrolyte level will get low and the battery will fail prematurely. Eventually it will fail anyway. In either case, one of the symptoms in this system of a failing battery is high battery voltage.

Replace or service your battery and yer good to go.

hope it helps
John
keeper
07-10-2009, 08:01 PM
Hi

i just bought that battery last year and just checked the water level. It was full. Forgive my ignorance, but how else do you service a battery?
Jeff_G
07-10-2009, 08:47 PM
A rectifier only system does not regulate voltage it only converts the voltage from the stator from AC to DC. Some modern batteries are built in such a way that they don't absorb voltage very well so they overcharge. You may want to try another battery or put a load on the system such as lights, radio etc. A higher load will help.
seahorse
07-10-2009, 10:28 PM
On an unregulated charging system, it is the battery that acts as a regulator. Get a large capacity group 27 deep cycle and you will see a difference.