Strange error mode with Sterling alternator regulator

[Chacal]

I have a pretty weird error mode with my Sterling advanced alternator regulator and like to hear any suggestions on how to resolve it.

My setup:
- Yanmar 3YM20 with the default Hitachi 60 amp alternator
- 2 x 110Ah sealed lead acid house batteries & 1 x 70Ah start separated by an automatic charging relay (0 voltage drop)
- Sterling advanced alternator regulator installed to regulate the alternator
- NASA battery monitor connected to the house bank

The problem:
- Everything worked fine for about a couple of months. Got better charging currents and higher charging voltages just as expected.
- Recently I have noticed the system going into a failure mode after starting the engine. This does not happen always, but often enough to be a problem.

The symptoms of the failure mode:
- Immediately after starting the engine, everything is fine. Charging light on the motor panel is not illuminated and the charger is not yet charging (the Hitachi as well as Sterling have some kind of slow start)
- When the charging begins (after a minute or so), the voltage at the alternator goes up to 17,7V
- The charging light turns on
- The alternator does not charge at all (no charge on NASA monitor & battery voltage around 12,7V)
- The Sterling unit does not light up any error/warning LEDs (only high charge, sealed lead acid/AGM battery selection & 12 V system voltage LEDs are on)

The only way to get out of this failure mode is to disconnect the field control wire (the white one) of the Sterling regulator. As soon as I do this, the charging starts normally using alternator's own internal regulator.

Has anyone seen anything similar? Any ideas about what might be going on?

 

[eagle160]

Hi. I've not had the exact same issue (mine was over charging to 15.5v after a few hours) and I'm not an expert, but did have issues with my setup which is not dissimilar (although I have a VP engine) so will give you my 2p. First off sterling are very quick in responding so might help to drop them a line. Expect response to be brief though... Secondly output of 17.7v on your Alternator shouldn't occur I would've thought, anything in excess of 14.2v might indicate broken internal regulator. There's an excess voltage alarm in the sterling regulator but mine didn't go off even when Alternator gave output of 16, it might be that this kicks in and stops charging if 17.7v is output on your Alternator? Might be an idea to measure output on the Alternator with a good voltage meter

My issue was a busted internal regulator which is easy to fix but a pain to find at reasonable cost (got it from Germany in the end for £50, volvo charge £280!!).

However, with sealed batteries you cannot get a real benefit from smart regulator (shouldn't charge at 14.6v like you can with refillable batteries) so in the end I haven't bothered to install mine after changing the internal regulator. So you might just want to have an easy life and leave sterling disconnecte?

 

[pvb]

Any ideas about what might be going on?

If the Sterling's voltage sensing wire has become disconnected, the Sterling regulator will increase the voltage dramatically. Try checking this wire.

Also, don't worry about using the Sterling with sealed batteries, they'll be fine.

 

[vyv_cox]

Also, don't worry about using the Sterling with sealed batteries, they'll be fine.

+1. I changed the setting on the Sterling when I replaced open cell with sealed batteries four years ago, no problems at all.

 

[Chacal]

First off sterling are very quick in responding so might help to drop them a line. Expect response to be brief though...

Yep, already did that. They are fast but brief, indeed. Didn't get too much help, however. They ended up suggesting re-measuring voltages pretty much everywhere - something I have already done quite a few times.

Secondly output of 17.7v on your Alternator shouldn't occur I would've thought, anything in excess of 14.2v might indicate broken internal regulator. There's an excess voltage alarm in the sterling regulator but mine didn't go off even when Alternator gave output of 16, it might be that this kicks in and stops charging if 17.7v is output on your Alternator? Might be an idea to measure output on the Alternator with a good voltage meter

The 17,7 V was measured from the alternator with a volt meter. The strange thing here is that when in the failure mode, the voltage between alternator poles is 17,7V, but the batteries are still not charging at all and voltage between battery poles is around 12,7V. I'm not that good in electrics, but I'm inclined to believe that this indicates some kind of short somewhere that short circuits the current from alternator and thus avoids reaching batteries?

My issue was a busted internal regulator which is easy to fix but a pain to find at reasonable cost (got it from Germany in the end for £50, volvo charge £280!!).

Did your setup work at all without Sterling? Mine works just fine when the white cable is disconnected. So the internal regulator can't be completely broken at least.. Probably worth checking still.

However, with sealed batteries you cannot get a real benefit from smart regulator (shouldn't charge at 14.6v like you can with refillable batteries) so in the end I haven't bothered to install mine after changing the internal regulator. So you might just want to have an easy life and leave sterling disconnecte?

During the first two months when the system worked fine, I was easily able to see the difference. Don't know about the Volvo alts, but Hitachi ones compensate quite heavily for rising temperature and this leads to decreasing charging currents very quickly. I could probably get something like 30 amps for a couple of minutes, but within 10 minutes the current was around 12-15 amps and still going down. With Sterling the amps stay above 30 much, much longer and only gradually come down as the batteries fill up.

If the Sterling's voltage sensing wire has become disconnected, the Sterling regulator will increase the voltage dramatically. Try checking this wire.

I checked this with a voltmeter and got the normal battery voltage. Should probably measure the negative cables (the black ones) as well as Sterling probably uses them as 0 volt reference..

Also, don't worry about using the Sterling with sealed batteries, they'll be fine.

Yep, thought so. I've been charging them with the 14,4 V setting, but heard stories about using even 14,8 V with success. Haven't tried that myself though..

 

[Chacal]

The 17,7 V was measured from the alternator with a volt meter. The strange thing here is that when in the failure mode, the voltage between alternator poles is 17,7V, but the batteries are still not charging at all and voltage between battery poles is around 12,7V. I'm not that good in electrics, but I'm inclined to believe that this indicates some kind of short somewhere that short circuits the current from alternator and thus avoids reaching batteries?

Ahaa! I just figured out what must be going on here..

I have a Blue Sea Systems automatic charging relay between the start & house banks and the alternator is connected to the start battery side of the relay. So, when the alternator goes berserk, the start battery side is the one that sees the high voltage. However, the charging relay has a high voltage safety feature that separates the banks if the voltage on either side goes above 16 V. This must be the reason I'm not seeing any charging on the house battery side. I haven't measured the start battery while the failure is on, but I bet that it has the 17,7 V on its poles.

So now the question remains.. What triggers the alternator to push out 17,7 volts when Sterling is connected?

 

[pvb]

So now the question remains.. What triggers the alternator to push out 17,7 volts when Sterling is connected?

Well, the Sterling unit could be faulty. Or, as I suggested earlier, the voltage sensing connection could be faulty. However, it's not a good idea to have a add-on regulator sensing a bank which isn't connected to the alternator, so I'd rewire the alternator output to the domestic bank, and let the relay take care of charging the start battery. If it worked OK before, though, that may not be the problem.

 

[eagle160]

My issue was dissimilar as my output on alternator was high (15.5v-16v) not at start but after few hours, and despite high output sterling Alternator kept on working. The fact that the sterling kept working in my case was odd, at least the built in high voltage alarm should have gone off but didn't. The setup worked fine with or without the sterling Alternator connected until after a few hours suddenly output on Alternator spiked (must be a change in charge cycle I guess).

Does your Alternator output 17.7v with sterling attached, and normal 14.2-14.6 ish without?

 

[Chacal]

Well, the Sterling unit could be faulty. Or, as I suggested earlier, the voltage sensing connection could be faulty. However, it's not a good idea to have a add-on regulator sensing a bank which isn't connected to the alternator, so I'd rewire the alternator output to the domestic bank, and let the relay take care of charging the start battery. If it worked OK before, though, that may not be the problem.

Yep, that was exactly what I figured out as well just after posting my last reply! Not quite sure, but the problem might indeed lie somewhere around the charging relay.

By the specs the relay combines the banks if the voltage on either side is above 13.6 V for 30 seconds or above 13 V for 2 minutes. So, in theory, it could happen that when the engine is started, the batteries are at rest at around 12.5 volts. Then when the charger starts charging, the voltage on the starter battery side goes up to whatever the alternator gives (probably over 13.6 anyway), but Sterling still sees the house battery voltage of around 12.5 as the relay has not yet combined the banks. If Sterling is then eager enough to raise the voltage above 16 volts before the relay combines the banks (in less than 30 seconds), the relay's over voltage safety feature kicks in and it never closes thus leaving Sterling to believe that the charged bank still has the 12.5 volts. This of course drives the Sterling to push the voltage up even more and the end results is the voltage is at 17.7 V and only the starter battery seeing this.

So, about everything working just fine for two months.. I just realised that the alternator is not the only element that can combine the banks as I also have a set of solar panels that are connected to the house bank side of the relay via an MPPT charging regulator. So, again in theory, if at the moment of starting the engine, the panels were producing enough power to charge the batteries, the banks would already be combined and Sterling could see the proper voltage right from the beginning. On the other hand, if the panels were not charging, the banks would be separated and the error situation could occur.

And now comes the funny part.. Just less than a week ago the sunniest continuous period in 35 years (more than 1,5 months of pure sun) ended here in Finland.. Go figure..

I think I'll disconnect the solar panels and see if I can then easily reproduce the problem.

 

[Chacal]

Just to fill in the latest news..

I did some more investigations yesterday and indeed the problem seems to be with the voltage sensing wire.

I disconnected the solar panels and put on some load to make sure that the relay was open. After that I started the engine and measured the voltage on both banks. Voltage at the starter battery started to climb immediately (obviously as the alternator is directly connected to it), but the house bank stayed at 12.6 V as the relay was open. I monitored the starter voltage and it climbed so fast that the relay did not manage to open until it hit the 16 V that is the over voltage safety limit of the relay. So now the situation was stuck the relay being in the safety disconnect mode and preventing Sterling to see the actual voltage of the batteries it was charging. This lead to ever increasing voltage until at 17.8 volts the fuse in Sterling blew. This effectively disabled the unit and the internal regulator of the alternator took over and lowered the voltage back to around 14 V.

After all this I removed the sensing wire from the house bank and connected it to the starter side and re-did the test. Now everything worked just fine. The voltage at the starter battery started to climb, but levelled off at around 14.3 V. Then the relay closed after some 30 seconds and charging continued normally to both banks.

So, we learned that one should never connect the sensing wire on the other side of the charging relay or other disconnect than the charging wires are connected - just as pvb already suggested!

 

[pvb]

Glad you got it sorted.