Checking volts at battery

[Darol Wester]

When checking an auto at the battery while it's running you get a little over 14 volts which shows it's charging. I'm having troubles with an Evinrude charging. The shop told me it should be putting out around 13-14 volts when checked at the battery. It's only showing 12.58. I checked a new Merc and that's what it's showing while running also.

Are these stators suppose to show more than the 12v range while running?

 

[ricksrster]

Re: Checking volts at battery

It should go up as you increase RPM and the battery becomes fully recharged. Not all motors have a voltage regulator. They just have a rectifier.

 

[Darol Wester]

Re: Checking volts at battery

The rectifier is new and so is the stator. When the battery is fully charged, and when reved up a bit it's showing 12.68 - 12.70 and idles back down to 12.58 on the meter. Does that sound about right?

 

[jtexas]

Re: Checking volts at battery

it's definately putting out some.....what's the battery voltage with the engine not running? fully charged should be at least 12.65, possible you're not getting a charge at idle - depending on your motor, you'd expect to see *something* over open circuit voltage at idle.................

 

[Darol Wester]

Re: Checking volts at battery

OK, I just checked it again and the battery is reading 12.69 before starting. After starting, it drops to 12.55 while the motor is running and comes up with RPM's. This is all new to me so I just want to make sure I've got it straight. Many thanks for your help. I live in a fairly remote area of Northern California and it's at least a 2 hour drive to the nearest boat shop so forums like this are really helpful. This is a great place.

 

[wcsparky05]

Re: Checking volts at battery

soooooo.... where is fort jones? i live 30 min east of sf. how far is that from you? (wc)

 

[Darol Wester]

Re: Checking volts at battery

Fort Jones is about twenty miles west of Yreka, up above Redding. It has a whopping population of almost 600. I live a few miles out side of it up against the Marble Mountain Wilderness in Quartz Valley. We do most of our boat fun at Trinity Lake south of here and out of Brookings Oregon in the salt.

We lived in Martinez in 90 & 92. Lots of stripper and sturgeon fishing and out to the Farallons and out of Bodega and Salt point for Salmon.

Also, had lots of fun at the Concord Pavilion. How's that new Benecia bridge....done yet?

 

[bruceb58]

Re: Checking volts at battery

You are definitely not charging.

 

[Darol Wester]

Re: Checking volts at battery

I have a brand new Merc 25hp and it shows the same type of readings. ?????????? On a fully charged battery with motor idling and with the RPM's up, what should the meter be showing?

 

[jtexas]

Re: Checking volts at battery

I can't speak from experience about brand new mercs, but..............I believe it should read higher at idle than with the engine not running. Did you have any accessories (livewell, stereo, lights, etc) running from the same battery when you took those readings? What year/hp is the evinrude?

 

[dingbat]

Re: Checking volts at battery

Not sure about the newer models, but I had a 86' Merc 175 and it didn't charge until you exceeded 2K RPM.

When trolling in the Spring I?d charge up the batteries on the way out and have to change over to the back up battery by noon to support the needs of the electronics.

 

[gunner1]

Re: Checking volts at battery

We lived in Martinez in 90 & 92. Lots of stripper and sturgeon fishing and out to the Farallons and out of Bodega and Salt point for Salmon.


What kind of "rod" do you use to catch those strippers? How about bait- nightcrawlers probably, huh?

 

[Boatist]

Re: Checking volts at battery

With the motor running you should get at least 13.8 volts. Normal range for a charging alternator is 13.8 volts to 14.8 volts. If you do not have anything drawing a lot of amps then ever at fast idle you should see at least 13.0 volts. By time you reach 1000 RPMS should be at least 13.8 amps

 

[Keith7481]

Re: Checking volts at battery

I was just looking at this thread and realized I have the opposite concern, perhaps a new thread. I recently had my alternator belt replaced. Since then, I've had reading in the 12+ range at idle. But at cruising speed it goes up to the 15 range and stays there. This occurs with no other load on the battery, no live well, no bilge, no lights etc. So, I'm wondering if I could be overcharging the battery and if so, should I be considering a new voltage regulator. As far as I can tell the battery is fully charged, I have a disconnect that I always use when the boat is not in use, but will stick a meter on it to be certain. Any thoughts on overcharging would be appreciated.
Keith

 

[jtexas]

Re: Checking volts at battery

keith, its generally a good idea to start a new thread with your question - no matter - if your battery is a marine deepcycle or dual purpose, I doubt 15V will hurt it - lot of boat motors have unregulated alternators, and a good marine battery will hold up to it - but I'm guessing yours is regulated. I think most regulators top out at 14 or 14.5 - sounds like yours is busted - don't know whether that has potential consequences other than battery - I'd fix it were it mine.

On the battery, check the water, check the voltage, check the specific gravity (hydrometer, couple bucks at autozone). With chronic overcharging can boil out the water leaving the plates exposed. Possible the battery's useful life has been shortened somewhat, but not likely you've toasted it. If you're worried about it, most auto parts stores will load test it for free - that's more or less the definitive test.

 

[Keith7481]

Re: Checking volts at battery

Thanks very much for those ideas. I thought I should also check all the connections, just in case a loose one is prompting overcharging. Only thing new is the disconnect I put in. But haven't had any problems starting so I doubt thats it. I have a shop MerC shop manual but it doesn't say much about changing a voltage regulator. It looks like it could either be built into the alternator (which would mean buying a new one) or could be separate like an auto. If the later, could I use one from an auto store?? Other than a constant high charge rate, on a full and well connected battery, any other way of testing the regulator that you know of?? Should I be using distilled water in the batt if its low?? I"ve only noticed the problem in the last 2 hrs of use, so not too worried about the battery yet Thanks again.

Keith

 

[jtexas]

Re: Checking volts at battery

yes, distilled water. marine electrics are generally built to avoid causing any exposed sparks on account of the engine being in an enclosed compartment potentially with gasoline fumes, is why automotive parts wouldn't be recommended in this case - sorry I'm not up on inboard or stern drive engines - if nobody else jumps in who knows more about your motor, a thread over on the mercruiser forum would probably get 'r' done.

 

[Keith7481]

Re: Checking volts at battery

I had a feeling that was the case, distilled and marine Vreg. I'll check the system and battery and try the other forum if no one else chimes in. Thanks again.
Keith

 

[Boatist]

Re: Checking volts at battery

Keith
My question is how did you check the 15 Volts? Did you use your dash voltmeter or a good digital volt meter? Dash voltmeters can be off quite a bit.
Is it a outboard or a I/O?
also try turning on a load, bildge blower, navagation lights and see what happends.

 

[Keith7481]

Re: Checking volts at battery

I've been using the meter on the boat which is an I/O. I was thinking the dash meter should be accurate, now I"m not so sure. Today, I was in some rough water and the gauge would vary from 15 to 11, with no change in rpm or load. At my previous post, when it registered 15 pretty steadily, I put a load on it, and the gauge would immediately register a voltage dropoff. When I shut down the load, it would return to 15. I'm starting to wonder if I have a loose connection, or just a bad voltage regulator. I think my next step is to buy a good voltmeter, put on the muffs start her up and see what I get, after tightening all of the connections. Is there any other way to test the regulator. THe battery is not getting hot, and I haven't had any problems with my battery being low. I did put a little water in two cells, but the batt seems ok.
Any other ideas?
Keith