Mastervolt charging problem

[All_at_Sea]

I’ve noticed for a while that the house batteries aren’t getting a very high charging current from the engine. It’s a 90A Mastervolt alternator running through their AlphaPro regulator. It’s hard to remember exactly, but I think I used to see 50-60A even at lowish engine revs (I think I used to never go above 1500rpm for charging). Over recent weeks I’ve had to run the engine for power several times and I’m not seeing many amps going in – 20-25 unless I crank the engine up to 2000rpm when I get about 40A. I decided to check connections & belt tension today and noticed that the alternator was getting very hot – too hot to touch after about 10mins at 2000 rpm.
I can’t find anyone in the alternator business locally and don’t know who to ask. Mastervolt point you to a “dealer” in Savannah but they don’t claim to even deal with alternators (I’ve emailed them but not heard back).
What do you think? Is reduced output & hot running a sign of failure, is it safe to use, can it be repaired???


This came in from friends sailing on the east coast of America, l wonder if the regulator is at fault but what do the collective minds think? I'll try and get hold of mastervolt today.

 

[Plevier]

My first question would be how confident are they in the health of the batteries? Are they getting long in the tooth and harder to charge?
I think high output alternators always get quite hot, maybe they haven't noticed before.

 

[dinwood]

Hi Guys, this is the originator of the question in the USA. The batteries are almost brand new, and you are right in that I've never felt the temperature of the alternator before, so it could be normal (but too hot to touch sounds like too hot to me, given that its current output is so much lower than its 90A capacity...). Someone locally suggested that a diode could have gone, but I've just checked and the output is pure DC (ie no AC voltage on the terminals). My next idea is to disconnect the belt and see if the bearings are running smoothly, a task for tomorrow now I'm back on board.

 

[William_H]

I would not hold too much confidence in your checking the output with a CRO looking for AC ripple if as is necessary the alternator is charging a battery. The battery would tend to smooth out any ripple I imagine. A shorted diode could (again I imagine) give overheating and low output. I would suggest removing the alternator for a bench check for output which any auto electrician should be able to do. Do it before the alternator is damged too much by heat. (ad for insulation) good luck olewill

 

[dinwood]

Hello again. I've done as many checks as I can, guided by friends and Nigel Calder's boatowner's manual.
1. The alternator spins freely and smoothly, no sign of bearing problems.
2. The AC ripple voltage is about 0.4V at full revs, under Calder's 0.5V limit
3. The diode test Calder describes shows high resistance one way and 0.8V the other - a normal result
4. Calder's leakage current test shows no measurable current using the 200micro-amp scale, also normal.
Yet I am left with an alternator getting very hot (I would say 60C in under 10 mins) yet producing a low current output (with batteries relatively discharged, 20A at 2000 rpm, whereas the Mastervolt manual implies 90% of capacity at these revs, ie 70A - I've never seen this in the past but have seen 50A at these revs).
I have just noticed that the Mastervolt AlphaPro regulator has both Bulk and Absorption light on, so I'm now wondering whether it is the regulator that is (also?) at fault.

Any help gratefully received!

 

[halcyon]

Hello again. I've done as many checks as I can, guided by friends and Nigel Calder's boatowner's manual.
1. The alternator spins freely and smoothly, no sign of bearing problems.
2. The AC ripple voltage is about 0.4V at full revs, under Calder's 0.5V limit
3. The diode test Calder describes shows high resistance one way and 0.8V the other - a normal result
4. Calder's leakage current test shows no measurable current using the 200micro-amp scale, also normal.
Yet I am left with an alternator getting very hot (I would say 60C in under 10 mins) yet producing a low current output (with batteries relatively discharged, 20A at 2000 rpm, whereas the Mastervolt manual implies 90% of capacity at these revs, ie 70A - I've never seen this in the past but have seen 50A at these revs).
I have just noticed that the Mastervolt AlphaPro regulator has both Bulk and Absorption light on, so I'm now wondering whether it is the regulator that is (also?) at fault.

Any help gratefully received!

Check voltage at battery and alternator on charge, low voltage would give a low current.

Which diodes did you check ?

Brian

 

[dinwood]

Hi, Voltage is good at the batteries; 14.3V
I did the Calder test, measuring across the +ve & ground terminals with all connections removed.

David

 

[Plevier]

What capacity are the batteries and what type?
Is your recollection of 50-60A with these batteries or with the previous ones (as you said these are nearly new)?

 

[dinwood]

I appreciate your help. The new batteries are 620Ah Lifeline AGM's, installed 6 months ago. The old ones were almost dead Mastervolt Gels. My memory of the higher charging current certainly goes back to the old batteries, but I'm pretty sure I saw those currents with the new ones, but perhaps that was from shore power. Now I really wish I kept records, but already accused of being amp obsessed, I'm not sure my 1st mate would put up with it!

 

[Plevier]

Interesting. I would have expected the Lifelines to take more current than the old gels.
However I know that Lifeline's like higher voltages than most AGMs and an occasional boost at a quite exceptional voltage, I think it's around 15.5. Have you read their tech manual thoroughly for charging conditions?
If they weren't freshly and thoroughly charged when you put them in they might want a boost to wake them up and get them in prime condition, but we are getting towards clutching at straws now.
SailingLegend is the forum's big Lifeline fan, maybe he will chip in.
I think the probability of its being the alternator is increasing, halcyon is a good adviser on that I think.
Not sure I can contribute any more as a battery man.