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Author Topic:   dead battery
captjohn posted 08-13-2005 07:14 AM ET (US)   Profile for captjohn   Send Email to captjohn  
I arrived home yesterday afternoon after spending 3 hours underway on my 1968 Nauset on Casco Bay accompanied by my Grandson. When I attemted to start the engine (94, 75 HP, Mariner)to flush same I discovered that i had a dead Battery. While out on the water I shut down once and then restarted without any problem. The battery is a new (this spring) Blue Top Optimax. How does one check if the alternator is operating correctly? Any suggestions would be appreciated. The previous day I installed a new Blue Seas Fused (6) position panel, new radio, GPS, etc.
John
tarbaby posted 08-13-2005 08:14 AM ET (US)     Profile for tarbaby  Send Email to tarbaby     
I would check your wiring on the panel first. Is there a short? Did you leave the radio or the GPS on? I also run Optima batteries and it takes a while for them to run down if I leave something "on".
jimh posted 08-13-2005 03:53 PM ET (US)     Profile for jimh  Send Email to jimh     
To check the charging system, monitor the battery terminal voltage when the motor is off and then again when it is on. When the motor is off the terminal voltage at the battery should be about 12.6 to 12.8 volts if well charged. When the engine is running the charging system should raise the battery voltage by about a volt or so, and you should see 13.5 to 14.0 volts at the battery terminals.

If you see more than 14 volts, your charing system may be not as well regulated as it could be. Some motors will put out more voltage, near 15-16 volts in some cases. If you do not see much of an increase in the battery voltage at all, you are probably not getting much, if any, charging current from your motor into the battery.

For more information about battery terminal voltage versus state of charge, see my article in the Reference section:

Battery Charge
http://continuouswave.com/whaler/reference/chargeBattery.html

Losing the charging output from a two-stroke outboard motor with an under-flywheel stator and rotating magnet type alternator is a common problem. If your charging system is not working, check the rectifier. Check the stator coil windings for opens or shunts to ground. Also check the regulator. I think on that model it may be a very simple shunt Zener diode regulator in a separate assembly from the rectifier. Also check for any fuses which have opened in the circuit that could affect its operation.

prxmid posted 08-14-2005 09:56 PM ET (US)     Profile for prxmid  Send Email to prxmid     
I have a battery problem also, but that last paragraph is like talking in tongues.

Is there an English translation somewhere?

captjohn posted 08-15-2005 05:48 AM ET (US)     Profile for captjohn  Send Email to captjohn     
I think my problem may have been the way I wired the Blue Seas panel. Hopefully I have rectified the situation. I will not know for certain until later this week when I launch the boat and am able to test the battery under operating conditions.
Thanks for the help I will advise you of my findings.
John

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