Alternator over charging?

[chrisbitz]

I've had a variety of problems with flat batteries, and I think I've discovered the issue.

My alternator appears to be giving out 15.6v at 1000revs. I've read that this is too much, so I guess I need to replace the voltage regulator?

It's a Volvo Penta 2010c. Is this an easyish job? are the regulators replaceable, or is it a sealed unit?

thanks!

 

[bikerbill]

I've had a variety of problems with flat batteries, and I think I've discovered the issue.

My alternator appears to be giving out 15.6v at 1000revs. I've read that this is too much, so I guess I need to replace the voltage regulator?

It's a Volvo Penta 2010c. Is this an easyish job? are the regulators replaceable, or is it a sealed unit?

thanks!

It should be reading 14.5 volts. I'm not familiar with the alternator from the Penta, but would guess it works the same as a car alternator. If so, the regulator in inside the . You can replace the diode/regulator board yourself if you know what your doing, but probably better to get it reconditioned then it would have new bearings also.

 

[VicS]

I've had a variety of problems with flat batteries, and I think I've discovered the issue.

My alternator appears to be giving out 15.6v at 1000revs. I've read that this is too much, so I guess I need to replace the voltage regulator?

It's a Volvo Penta 2010c. Is this an easyish job? are the regulators replaceable, or is it a sealed unit?

thanks!

If you have some fprm of fancy regulator that may be at fault.

If you have split charging with a diode splitter and battery sensing check the battery sensing connection.

Otherwise almost certainly the regulator at fault.

Provided you can get a regulator it may be a simple matter to replace it. Some come complete with the brush assembly.

Unless you are happy to dabble with the alternator take it to an Automobile electricians.

Curd Brothers in Tunbridge Wells have a good reputation locally and are not a million miles from you. ( I used then two or three times but I must admit they are not cheap.

 

[Sans Bateau]

You need to check the batteries, you may have a duff cell, the alternator is trying to charge a battery which it never will. Check each one with a volt meter. I think that may be the problem.

 

[VicS]

You need to check the batteries, you may have a duff cell, the alternator is trying to charge a battery which it never will. Check each one with a volt meter. I think that may be the problem.

Standard alternator still should not output 15.6 volts

 

[bikerbill]

Standard alternator still should not output 15.6 volts

As mentioned before, best to check the batteries first. The alternator may produce a higher output than the normal 14.5v if the battery is totally knackered. A few years ago I bought a Pan European ST100 (motorbike) that had been off the road for 7 years. I jump started it, tested the alternator output which read 18v if I remember. I thought that there was a problem with the alternator. However, a new battery fitted, tested again, this time the output was 14.5v. Perhaps the alternator was trying too hard to put a charge into the dead battery.

 

[chrisbitz]

It's quite possible that one of the batteries was a dud, as when I put the switch to 2 only, the engine revs rose, but when I put it to 1 only they came back down about 200 revs.

However the voltage didn't change with the switching...
Does that change anything?

 

[VicS]

As mentioned before, best to check the batteries first. The alternator may produce a higher output than the normal 14.5v if the battery is totally knackered. A few years ago I bought a Pan European ST100 (motorbike) that had been off the road for 7 years. I jump started it, tested the alternator output which read 18v if I remember. I thought that there was a problem with the alternator. However, a new battery fitted, tested again, this time the output was 14.5v. Perhaps the alternator was trying too hard to put a charge into the dead battery.

What sort of alternator was that though ? Quite common for then "no load" voltage from an unregulated charging coil/rectifier in a magneto to rise to that sort of figure.

 

[VicS]

It's quite possible that one of the batteries was a dud, as when I put the switch to 2 only, the engine revs rose, but when I put it to 1 only they came back down about 200 revs.

However the voltage didn't change with the switching...
Does that change anything?

Check the batteries by all means and all the connections but what you now say adds weight to the idea that the alternator regulator is faulty.

 

[lw395]

As mentioned before, best to check the batteries first. The alternator may produce a higher output than the normal 14.5v if the battery is totally knackered. A few years ago I bought a Pan European ST100 (motorbike) that had been off the road for 7 years. I jump started it, tested the alternator output which read 18v if I remember. I thought that there was a problem with the alternator. However, a new battery fitted, tested again, this time the output was 14.5v. Perhaps the alternator was trying too hard to put a charge into the dead battery.

Many motorbikes have a series regulator with a permanent magnet rotor instead of controlling the field current like a car alternator. Different animal. With no battery they will give lots of volts at no current.
A car alternator may give high volts if completely unloaded, it will probably be a rough waveform meaning you need to know if your meter is reading peak, mean or RMS. Best to draw a bit of current for a realistic test.
Some alternators can even blow up with no battery or a totally shot battery.