Over charging?

[muskyjim]

I apologize for asking this question again. I used the wrong forum the first time.
I have a 1979 70hp Johnson Sea Horse. At Idle it is charging around 14. The faster I go the charge creeps to as high as 17.5. This is double verified by the voltage gage on the console and my depth finder. I'm told there is no alternator or voltage regulator on this motor. It has also been suggested that my starting battery is at fault and I should replace it. This is not a sealed battery I check the water level often and rarely add water. It doesn't overheat or boil over. It reads 12.0 volts at a volt meter when fully charged and at rest.
Obviously I'm not an electrician. So how does the battery charge. If the battery is at fault, could I replace it with a sealed marine battery, ( Optima )?
Thanks in advance for the education.
muskyjim

 

[Texasmark]

Re: Over charging?

You ain't-a-gonna get 17v without a built in charger, nor 14 for that matter.

I use 12.75 volts (Standard Temperature and Pressure.....STP) for my fully charged batteries.

Most chargers run in the 14.5 ish range to recharge your battery at say 1000 or so rpm's. 17v indicates a charger on the engine and the regulator has quit regulating.

Normally that much voltage will boil the water out of the battery if allowed to charge for any length of time. First clue is to feel the side of the battery and it will be warm to hot.

If you aren't boiling water out it is because you have a newer battery, usually sealed, designed with different chemicals to reduce boil over....hence no need to add water.

12v at rest is a discharged battery to me.

Additionally I don't know what kind of meter you are using nor what your STP is which will affect your readings.

HTH,

Mark

 

[jlinder]

Re: Over charging?

What you are reporting is confusing.

If you have 17.5 on the battery you would be over charging. If you do this for a while the battery overheats severely and the water boils out. But.you are not adding water.

You say you are reading 12.0 volts. If you were charging the battery as you say you would see 12.6 or more.

Confusing.

Have you tried measuring the voltage at the battery with the motor running? Not with the dash voltmeter, but with one connected directly to the battery. I suspect you will read something different.

If you read something different, try using the same meter to read closer to the dash voltmeter (fuseblock?).

The more readings you get the better chance you have in diagnosing the problem.

 

[Texasmark]

Re: Over charging?

Yeah J, that's how it looked to me too.....confusing readings.

Mark

 

[eurolarva]

Re: Over charging?

If you are getting 17 at high RPM and 14 at idle chances are your motor has an alternator, a rectifier and no voltage regulator. How old is the battery? Typically most marine batteries will only get you about 3 years till they start crapping out. I would have the battery load tested or use a hydormeter to test it. Older outboards with no regulation this is common and is usually bad, loose or corroded battery connections or a bad battery.

 

[Texasmark]

Re: Over charging?

I may be wrong here euro, but back when there were no regulators the generators/alternators only put out miniscule current (like 8 amperes) and you didn't need one.

After somebody figured out that most boaters run accessories, the amperage race started and with a pair of 20 ampere rectifiers supplying 40 amps peak to a battery (Merc 150 for 1) you had better have it under control.

But I agree with you that without one the voltage will be all over the place.......but 12v is a dead battery to me.

Mark

 

[eurolarva]

Re: Over charging?

I think that is the problem. Dead battery. I have read this same thing in the force forums. Marine batteries dont last like car batteries. A day after the battery is fully charged with a regular charger the voltage should be around 12.65 Volts. I cant remember the chart but It seems to me a 12.40 Volt battery is around 50 percent.

 

[Boatist]

Re: Over charging?

What kind of meter are you useing to messure your voltage? At 70 or 80 degrees you charged battery should be 12.6 volts. Temperature will make some difference. 12.0 volts is a very weak battery.

Older outboards offten did not have regulators. If this is the case try turning some load and see if the voltage drops some. 17 Volts is too high for your battery and all your electronics. Most electronics designed for 13.8 volts. Most will take more voltage without damage but 17 is quite high.

My 1980 boat has never had any battery that did not last 6 years, starting or deep cycle. I do not like the Optima battery at all. Just think it over priced and does not hold up well.

 

[muskyjim]

Re: Over charging?

I had my starting battery and my deep cycle both load tested. They are both are in great condition. I was going off of memory when I gave the resting battery charge voltage. It is where it should be.
" The unregulated charging system on all 2- and 3- cylinder and some V4 engines consists of a flywheel with cast-in magnets, the stator assembly, a rectifier and the battery." As stated by my Clymer E and J OB. shop manual.
The over charging is probaly the result of a faulty rectifier. When I pull it out of winter storage I will change out the old rectifier. I will however check the voltage at the battery as suggested while it is running. It's not going to hurt to replace the old rectifier anyway. I checked the wiring and the connections and they all seem to be good as well.
I'm starting my third year with the Optima deep cycle, and my starting battery. I haven't put alot of hours on either. When they do crap out I will probably come back to this forum and get one of the recommended batteries you guys suggest.
I agree that the Optima isn't all it's cracked up to be. But it does seem to give me plenty of time on the water during my fishing trips before it needs to be recharged, most times a bit more than the other boats in our group under the same conditions.
Thanks for the help.