Alternator overcharging ?

[Joker2]

Got a new Optima Blue top battery this year went out and noticed when going 2000 or more Rpm's my voltmeter ( new ) goes up to 17 / 18 volts. Checked it with a known good meter at the battery while underway. sure enough it read 17.5 V. Didn't have this problem last year with old battery, I didn't change anything as far as electronics go. How bad is this and how do I fix it, or at least troubleshoot the problem ? Thanks

[THEFERMANATOR]

OPTIMA batteries are of an AGM design that have very low internal resistance and will run pretty high voltages compared to a lead acid battery in an unregulated charging system. If this is with your 150 EVINRUDE though, sounds like you have a voltage regulator issue. Check the connections espescially the ground at the regulator is the first thing I would do. You shouldn't get much higher than about 14.5 or so if the regulator is working properly. I know AGM batteries don't take well to running at high voltages for extended periods of time and will die a short death doing so.

[Joker2]

Thanks , I will check that out.

[Joker2]

I was wondering why my fishfinder is not shutting down when the Alternator is putting out 17.5V, it's just a cheap $120.00 Lowrance lcd unit ?

[THEFERMANATOR]

Originally Posted by Joker2

I was wondering why my fishfinder is not shutting down when the Alternator is putting out 17.5V, it's just a cheap $120.00 Lowrance lcd unit ?

Alot of marine electrronics can run on both 12 or 24V as some boats run 24V systems in them.

[phatdaddy]

i think one of my garmin units has an operating range of 10-20 volts