Alternator controller problem

[Mac of Cygnet]

I have a Sterling 4-stage alternator controller (as well as the internal alternator controller, I understand) which can be switched off. When on, the voltage on the control panel usually starts at about 14.5V, quickly climbs to about 15.5V, then gradually subsides back to about 14.2V, the same as when it is switched off. Last autumn (about 40 engine hours ago), the needle started swinging wildly between 14.2V to off the scale before returning to normal.

 

It is now always off the scale (over16V) when the controller is switched on, and indeed using my very basic multimeter it seems the batteries are receiving about 19V, which I'm sure can't be good for them.

 

The various alternator controller lights seem to be as normal; the red 'High Voltage Trip Warning' does not come on.

 

Any idea what I should be looking at here?

 

Thanks

 

Mac

[The Lockie]

How about disconnecting the field control wire from the sterling...the one that goes to the back of the alternator and see what happens?? If voltage still high then unlikely to be a fault on the sterling

 

Just an opinion iam no expert at your own risk etc etc...

[cereal tiller]

How about disconnecting the field control wire from the sterling...the one that goes to the back of the alternator and see what happens?? If voltage still high then unlikely to be a fault on the sterling

 

Just an opinion iam no expert at your own risk etc etc...

Good idea,and also check all connections to alternator and the Red and Black/white to main battery pos. and neg.

 

The Field wire that Lockie mentions is usually White, but Green on older Controllers

 

 

 

CT

[b0atman]

my sterling alternator failed to my mind un safely by ramping voltage high

[Mac of Cygnet]

Thanks for replies. I've spent most of the afternoon on this, tracing the labyrinthine wiring of this system. After reading the leaflet that came with the controller (before my time), and despite the high voltage trip not coming on, I did what it suggested and measured the voltage drop between alternator and batteries. Result: leisure batteries 3V, starter battery 0.1V Sterling say it should be 2.5V including cables and split charge diode (or relay).

 

Next I tried it with a direct connection (jump lead) from alternator to leisure batteries. Result: voltage back to what it should be, but with needle jumping around. Went searching for the diode or relay. Couldn't find it. Anyone any idea where it might be? (small Vetus engine). Found two relays which are heater plugs and starter.

 

Anyway, after all this messing around, lo and behold I switched the controller on again, and it's back to the situation for most of last summer - about the right voltage, needle jumping around a bit but eventually settling down. So it looks like one of those really annoying intermittent faults which are just beyond me.

[WotEver]

... measured the voltage drop between alternator and batteries. Result: leisure batteries 3V...

Wow! You sure you don't mean 0.3V? 3V drop is HUGE!

 

Clean and tighten all the connections and if it's still the same then rewire with some proper cable.

 

Tony

[Mac of Cygnet]

Wow! You sure you don't mean 0.3V? 3V drop is HUGE!

 

Clean and tighten all the connections and if it's still the same then rewire with some proper cable.

 

Tony

 

Sterling say it should be no more than 2.5V, (1.0V for the cables + 1.5V for the diode) but what do I know? Anyway, now that it has spontaneously almost gone back to normal, both starter and leisure voltage drops are about 0.1V My electrical knowledge is basic, to say the least.

[Tony Brooks]

 

Sterling say it should be no more than 2.5V, (1.0V for the cables + 1.5V for the diode) but what do I know? Anyway, now that it has spontaneously almost gone back to normal, both starter and leisure voltage drops are about 0.1V My electrical knowledge is basic, to say the least.

 

I agree with Nick, a split charge diode should only drop around 0.5 to 0.7 V and any cabling around 0.3V so that's 1V absolutely tops. Some so called split charge diodes drop far less than that. - so called zero volt drop products.

 

Some, if not all Vetus alternators are battery sensing so the fault could be with the alternator's battery sense wire if it has one, not the controller. Disconnecting the wire between controller and alternator field would rule this in or out. I would say that ammeters waving about tend not to be a good sign. I am wondering if you have a dry joint on one of the field diodes. This might give a very erratic output and a high voltage. Again disconnecting the controller would prove or disprove it.

 

If you have a split charge diode it should have three thick wires on it. One from the alternator, one going to the engine battery and one to the domestic battery. It will more often than not be black with some kind of finning on it but Lucas did/do make one that looks like an old car's ignition coil.

 

A split charge relay will have two thick wires on it and one or two thin wires. The thick wire will run from one battery bank to the relay and then from the relay to the other bank.

 

Because the wires should be as thick as the main alternator cables for both relays and diodes they should be easy to trace. I think the relays you found are on the engine. The diode or split charge relay is more likely to be off the engine but not too far away so the cable lengths are minimised.

 

Photos of the engine area and wiring may help and if you can find an alternator number SirN or Steve (Eeyore) may be able to say if it is battery or machine sensed.

[junior]

I had this problem before Christmas. I won't tell you how many different people changed parts, wores, etc. We even replaced the alternator and disconnected the wires from the Stirling Controller. This went on for about 6 weeks.

 

What I will tell you is that the cause of all the problems was that a battery needed topping up. Except I'd killed it and ended up having to replace the battery.

 

The plus side is that I have a shiny new updated alternator.

 

2 other points to note is that the Stirling device wasn't reconnected and it all still works just as well. Secondly, don't update your alternator without updating the ammeter ;-)

[Tony Brooks]

snip

 

2 other points to note is that the Stirling device wasn't reconnected and it all still works just as well. Secondly, don't update your alternator without updating the ammeter ;-)

 

That rather depends upon the existing ammeter's or the shunt's rating.

[WotEver]

 

I agree with Nick...

Or even Tony

 

... the Stirling device wasn't reconnected and it all still works just as well.

Absolutely, you have a modern alternator. There is no need whatsoever for an alt controller with one as you have seen. All it does is add complexity and give something else to go wrong.

 

Tony

Edited April 28, 2016 by WotEver

[Tony Brooks]

Or even Tony

 

Absolutely, you have a modern alternator. There is no need whatsoever for an alt controller with one as you have seen. All it does is add complexity and give something else to go wrong.

 

Tony

Yes, sorry.

 

 

 

I have been giving the Sterling figure more thought and maybe the OP has not understood the potential source of the problem.

 

I think we are all saying that voltdrop along the controller's battery SENSE wire would cause a high charging voltage and that should have zero voltdrop on it as it carries all but zero current.

 

The Sterling figures relate, I think, to the voltdrop on the charging leads and although two Tonys question the figures there is an explanation. The controller is battery sensed so as long as the voltdrop on the charging leads is less than the maximum voltage boost the controller is set to provide it will not really matter what the voltdrop is on the charging leads, it will be compensated for.

 

I think Sterling are really saying the maximum voltage boost the controller can provide is 2.5V so as long as the voltdrop on the charging leads is less than this it will still work.

 

Edited April 28, 2016 by Tony Brooks

[WotEver]

 

I think Sterling are really saying the maximum voltage boost the controller can provide is 2.5V so as long as the voltdrop on the charging leads is less than this it will still work.

 

I suspect you're right however this means that the controller will potentially be forcing the alternator up to 17.3V - way above its design parameters - simply because the installation is exceedingly poor.

 

Better to fix the installation. Cheaper too.

 

Tony

[Tony Brooks]

I suspect you're right however this means that the controller will potentially be forcing the alternator up to 17.3V - way above its design parameters - simply because the installation is exceedingly poor.

 

Better to fix the installation. Cheaper too.

 

Tony

 

Agreed.

[Mac of Cygnet]

 

 

 

 

Because the wires should be as thick as the main alternator cables for both relays and diodes they should be easy to trace. I think the relays you found are on the engine. The diode or split charge relay is more likely to be off the engine but not too far away so the cable lengths are minimised.

 

Photos of the engine area and wiring may help and if you can find an alternator number SirN or Steve (Eeyore) may be able to say if it is battery or machine sensed.

 

I'm suffering from information overload! But don't think I'm not grateful.

 

The bit I've left in Tony's post is the only one I can sensibly reply to. There are indeed thick red wires coming from the 2 leisure batteries (one each, despite the batteries being connected) and the starter battery, and these I was trying to trace. Not easy, despite what you say - they all disappear into the engine hole bulkhead and for the life of me I cannot find them emerging ANYWHERE! Similarly the alternator charging cable disappears under the engine and I can't even get my slim arms down there to follow it or see where it goes - I think it must disappear into an anonymous sleeve, but I guess it goes where the other three go. Even the alternator is very difficult to access the back of.

 

I'm home from the boat just now, but I'll have a look at the various suggestions when I next visit (I would normally be off on my travels by now but can't go anywhere because of the C&H and Rochdale situation.)

 

Meanwhile I would guess that if the symptoms reappear then I can just turn off the Sterling controller and rely on the alternator's own until I can find someone to make sense of it all on the spot?

[dor]

Or even Tony

 

Absolutely, you have a modern alternator. There is no need whatsoever for an alt controller with one as you have seen. All it does is add complexity and give something else to go wrong.

 

Tony

 

Although even modern alternators don't always regulate at the optimum rate. My recent Vetus replacement alternator is still regulated at 14.0 volts, as is my almost new car with "stop and go" technology which requires a well charged battery to operate.

 

Of course, external alternators don't have to be the answer. My old Vetus alternator was repaired and at the same time I asked if it could be fitted with a 14.4V regulator. These cost about £15 on ebay and do pretty much as much as the fancy external controllers do.

 

I now wish I had asked for a 14.6 V regulator or even a bit higher as water loss from batteries seems to be much less of a problem with modern batteries.