Hitachi alternator from H27, output = 11 volts. 
Next question, where do I get a voltage regulator?
Next question, where do I get a voltage regulator?
Alternator Test Results
- Thread starter braol
- Start date
I saved this a long time ago. What state of charge were your batteries in, where did you measure the voltage, how many rpms and how long after you started your engine?
Hitachi/Yanmar Alternators: (by Maine Sail)
Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?
Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorbtion voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?
The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....
If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.
If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.
This is from:
http://forums.sbo.sailboatowners.com/showthread.php?t=125392
and this, too:
http://www.cruisersforum.com/forums...d-smart-regulator-instal-question-125843.html
Hitachi/Yanmar Alternators: (by Maine Sail)
Some alternators though, such as those made by Hitachi and found on Yanmar diesels, are dumber than a pound of beetle poop. Actually, to the alternator, they are pretty smart but to your batteries and the speed of charging they are flat out stupid. Why?
Hitachi alts with dumb regulators, and some others, limit voltage but also reduce voltage based on alternator temperature. This is a self protective feature installed in the internal dumb regulator to prevent the alternator from cooking itself. Remember voltage is the pressure that allows more current to flow. So, if we reduce the absorbtion voltage, then we also reduce the current the alternator is supplying.. The battery simply will not accept the same current at 13.4V that it did at 14.4V and as a result the alternator will run cooler. What do you suppose this does to your batteries over time.......?
The problem is that when cold you will get 14.3V to 14.4V out of the Hitachi but as the alternator heats up the dumb regulator begins to reduce the CV/voltage limit based on the alternators internal temperature. It is not uncommon to find a Hitachi alternator at 13.4V when hot. This is REALLY, REALLY DUMB....
If you have a dumb regulator, and notice the voltage dropping, it is likely a temp compensated dumb regulator. Get rid of it or plan to buy new batteries more often.
If you have a temp compensated alternator or a Hitachi alternator on a Yanmar you really are in dire need of external regulation if deep cycling a larger battery bank.
This is from:
http://forums.sbo.sailboatowners.com/showthread.php?t=125392
and this, too:
http://www.cruisersforum.com/forums...d-smart-regulator-instal-question-125843.html
If you are reading 11 volts then something beyond dumb is happening. no alternator is going to "output" a voltage of 11 volts unless it is trying to charge a VERY large battery bank that is VERY deeply discharged. 11 volts would have current flowing from battery TO the alternator!!!!
my guess is that one of the internal diodes has failed. have alternator rebuilt.Hitachi alternator from H27, output = 11 volts.
Alternator was pushing 11 volts on a test stand, not in the boat. I'm leaning towards diodes. There's a good electric shop in Waukegan, IL that rebuilds alternators/generators..so I'll see what they say. Hopefully not too many $$$$.
If the rebuild looks too expensive, you might consider a new one. Doesn't have to be the same kind, just needs the same mounting foot, and I think there's only two or three different types. I got a 55 amp marine alt from a local shop about ten years ago for $130. Would be more now though. Or it might be a good time to upgrade to a "real" alternator, high output with smart regulator.
Diodes will not effect the voltage output, they will effect the current though. Check the slip rings for good conductivity as they supply the current for the rotor magnetic field which makes the stator (stationary) windings produce voltage. Low field current, smaller magnetic field and less voltage output.
On a test stand they "full field" the rotor so it will be producing max output. If you can't full field it then ........ resistance in the slip rings/brushes