15.8 V charging - alternator shot?

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RadiumRob

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Hi,

Boat has a Penta 2002 with two brand new Numax 100Ah batteries, usually operating independently through a 1-2-B switch.

I left the Rutland wind genny charging the house battery overnight. The next morning the house battery was charging at 13.7V, nominally full according to the BM1 battery monitor which is connected to that battery. I turned off the wind genny, the house battery settled to 12.7V.

I then started the engine on the starter battery, the BM1 showed 13.7V. Ran the engine for a while then switched to Both. Engine revs dropped, BM1 shot up to 15.8V, charging at between 10 - 30A. Switched to house battery alone, BM1 settled back to 14.4V, charging ~2 A, revs picked up.

The alternator seems to be overcharging when connected to the full bank, so I'm wondering if the regulator could be at fault. But I'm also perplexed by the BM1's behaviour, which as far as I am aware is only connected to the house battery (although I believe there is a facility to show the voltage only of the engine battery but this requires user intervention if wired correctly).

Any ideas as to the potential cause of both?

Thanks,
 
I'll be interested to see what the experts say but

"Engine revs dropped, BM1 shot up to 15.8V"

That would indicate that one of your new batteries is a dud to me. (Maybe there is a load on the battery- something not switching off?)
 
I would see that 14.4v and 2 amps into a fully charged house battery suggests that the regulator is OK.
Can't explain the high charge voltage/ current though, unless your 1-2-B switch is wired in a strange way, somehow loading the alternator.
 
RadiumRob said:
Hi,

Boat has a Penta 2002 with two brand new Numax 100Ah batteries, usually operating independently through a 1-2-B switch.

I left the Rutland wind genny charging the house battery overnight. The next morning the house battery was charging at 13.7V, nominally full according to the BM1 battery monitor which is connected to that battery. I turned off the wind genny, the house battery settled to 12.7V.

I then started the engine on the starter battery, the BM1 showed 13.7V. Ran the engine for a while then switched to Both. Engine revs dropped, BM1 shot up to 15.8V, charging at between 10 - 30A. Switched to house battery alone, BM1 settled back to 14.4V, charging ~2 A, revs picked up.

The alternator seems to be overcharging when connected to the full bank, so I'm wondering if the regulator could be at fault. But I'm also perplexed by the BM1's behaviour, which as far as I am aware is only connected to the house battery (although I believe there is a facility to show the voltage only of the engine battery but this requires user intervention if wired correctly).

Any ideas as to the potential cause of both?

Thanks,
Click to expand...

Try no feed to voltage sense on alternator from service battery, may be a wire not connected or to wrong battery, i.e engine.

Brian
 
Thanks,

All -ve cables go through isolator switch so I'm fairly sure the battery hasn't been drained, plus I checked with a multimeter and both were at 12.7v.

The voltage sensing cable fault seems feasible. There were previously four batteries and I have rationalised down to two but all cables that were originally connected are now. Is there any way to test/check that hypothesis?
 
RadiumRob said:
Thanks,

All -ve cables go through isolator switch so I'm fairly sure the battery hasn't been drained, plus I checked with a multimeter and both were at 12.7v.

The voltage sensing cable fault seems feasible. There were previously four batteries and I have rationalised down to two but all cables that were originally connected are now. Is there any way to test/check that hypothesis?
Click to expand...

Put meter on alternator sense terminal and ground, select service battery, did the voltage change ? did it match the battery bank.

The voltage you see would match charging a near full battery with that load, but with no voltage regulation, is it machine or battery sensed alternator ?

Brian

Brian
 
I had a problem with my alternator where on starting the engine the battery was charging at 14.2v but the voltage then rapidly climbed to 15.8v and stayed there. I replaced the alternator regulator and that solved the problem. Second time it's happened in a nine year period and the chap who sold me the regulator commented that he kept a stock of them as they often failed in this manner.
 
The same happened to me and it was the alternator regulator. I was prepared to buy a new alternator but my electrician said there was nothing wrong with the alternator
and changing the regulator would be fine, which it was and still is.
 
My thoughts wer that it is either a problem with battery voltage sensing or a defective alternator regulator.


The fact that it appears to operate correctly when only the house battery is selected suggests that there is nothing wrong with the regulator, but if all else fails get the alternator tested by an auto-electrician

As originally supplied by VP ITYWF that the alternator would have been machine sensed.
If it is now battery sensed then either it has been modified or replaced by a battery sensing one

If there is battery sensing then the sensing connection should be the "common" terminal of the 12B switch so that the alternator cannot be charging one battery while the sensing is connected to the other.
If there is a problem here though you'd expect it to be OK when both batteries are selected.

Is there any fancy alternator controller such as a Sterling or other similar gizmo that you have not told us about ?

It would be interesting to know what the voltage is when only the starter battery is charging. You could measure this with a separate meter or with the BM1 if it has the facility and it is connected.

.Check all connections.
 
Last edited:
Vic,

As far as I can tell there is just one small cable from the common post of the 1-2-B switch, which I presume goes to the +ve bus bar. I don't think there is a fancy controller installed, it al looks fairly standard/dated. I'll measure the charge voltage on the starter battery at the weekend.

Thanks.
 
ditchcrawler said:
The same happened to me and it was the alternator regulator. I was prepared to buy a new alternator but my electrician said there was nothing wrong with the alternator
and changing the regulator would be fine, which it was and still is.
Click to expand...

That's interesting - did you see the elevated voltage on both batteries or just one? From what VicS has said, it seems likely the regulator is ok since the voltage/current is normal when connected to the engine battery.
 
halcyon said:
Put meter on alternator sense terminal and ground, select service battery, did the voltage change ? did it match the battery bank.

The voltage you see would match charging a near full battery with that load, but with no voltage regulation, is it machine or battery sensed alternator ?

Brian

Brian
Click to expand...

Thanks Brian, I'll give that a try at the weekend.
 
Both battery banks had the raised voltage via the 1/2/3 switch . At first my friend thought it was the Sterling Alternator Management system and he tried a spare that he had, but no difference.
I have 2 100 a/h Numax as domestics and a Red Flash AGM as my starter and I like the 1/2/3 which I have had on all my boats.
 
RadiumRob said:
Vic,

As far as I can tell there is just one small cable from the common post of the 1-2-B switch, which I presume goes to the +ve bus bar. I don't think there is a fancy controller installed, it al looks fairly standard/dated. I'll measure the charge voltage on the starter battery at the weekend.

Thanks.
Click to expand...

"..............just one small cable from the common post..............."

Do you mean in addition to a heavy cable. or one small cable only ?

I'd expect to see a heavy cable, battery cable size, if the 1,2,B switch is controlling the charging and use, including starting.
 
RadiumRob said:
Thanks Brian, I'll give that a try at the weekend.
Click to expand...

Does the engine need a 12 volt supply to keep it running, that is no electronic engine management, stop solenoid ? just a thought that in rewiring the batteries you have lost earth from service battery to engine, hence no regulation.

Brian
 
halcyon said:
Does the engine need a 12 volt supply to keep it running, that is no electronic engine management, stop solenoid ? just a thought that in rewiring the batteries you have lost earth from service battery to engine, hence no regulation.

Brian
Click to expand...

Mecahnical stop onthe 2002. Power is only needed, once it is running, for the alarms and tachometer
 
Are you sure that you haven’t got something like a Sterling intelligent battery management system that was previously wired in somewhere?

We have one and it will vary the charge that your battery bank receives, sometimes up to 15+ volts, but it will eventually come back down once it’s happy that the battery is happy. I’m no expert, but it’s supposed to prevent sulphation of the plates in the battery. Having just replaced my twin 110AH lead acid battery bank after 15 years of use (and one of them was still perfectly fine), I’d say the Sterling system has done a Sterling job.

Have a good look around, as there may be one installed out of the way. If so, it’s doing what it’s supossed to do and i wouldn’t worry any more.
 
KAL said:
Are you sure that you haven’t got something like a Sterling intelligent battery management system that was previously wired in somewhere?

We have one and it will vary the charge that your battery bank receives, sometimes up to 15+ volts, but it will eventually come back down once it’s happy that the battery is happy. I’m no expert, but it’s supposed to prevent sulphation of the plates in the battery. Having just replaced my twin 110AH lead acid battery bank after 15 years of use (and one of them was still perfectly fine), I’d say the Sterling system has done a Sterling job.

Have a good look around, as there may be one installed out of the way. If so, it’s doing what it’s supossed to do and i wouldn’t worry any more.
Click to expand...

There is a Sterling ProCharge D battery charger, but this is shorepower only. There's no sign of anything additional in the engine bay, and nothing was mentioned in the boat's spec at sale.

Thanks
 
Vic,

I don't have a manual for the Plastimo 1-2-B switch so I may be mis-identifying the terminals. I have attached a picture. AFAIK the top terminal is Battery 2, the right hand one is Battery 1, and the left one is the output (what I assume is the common terminal), which is a single wire leading to the distribution board.

Presumably the absence of any other cable on the output terminal suggests the regulator is machine sensed, not battery.

Thanks,

Rob

Plastimo 1-2-B.jpg
 
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