Alternator/battery/other shenanigans... any ideas please?

[Ewan123]

Edit to add more pics and a spare earth cable hanging around by the stbd alternator...

 

Two alternators - Port (primarily for starter battery and bow thruster I think) and Starboard (primarily domestic battery I think) (Starboard most do a bit of both I think...)

 

When the + is connected on the Port alternator, the starter battery voltage goes crazy (15V at idle, jumps up and down above that if engine revved higher and the engine also responds to the jumping voltage).

 

When the Port + ve is disconnected, the starter charges slowly (13V and slowly rising) at idle and higher revs. Domestics charge normally. 

While discovering this, the battery monitoring panel (Mastervolt Combi control panel,  connected to the shunt on -ve cable and to the inverter) died - no display shows at all now.

 

Prior to this, the engine STOP button stopped working, the switch and its nearest fuse is OK, need to check the solenoid and/or more fuses. I also swapped in a new starter battery as the old was going flat/ failing to start the engine. 

 

I can't think when that Port +ve might have been disconnected. 

 

No fuses I can find have blown.

 

I believe these original diagrams are still correct... except that solar has since been added.

 

 

Port

 

Starboard 

Edited February 12, 2022 by Ewan123

[Tracy D'arth]

Beta engine?

 

Check the multi plugs and sockets on the engine loom to control panel, there may be two pairs.

[David Mack]

8 minutes ago, Ewan123 said:

Two alternators - Port (primarily for starter battery and bow thruster I think) and Starboard (primarily domestic battery I think) (Starboard most do a bit of both I think...)

If those diagrams are correct then you have two separate systems, and so the port alternator charges just the starter and BT batteries, and the starboard just the domestic.

 

When you say the port + is disconnected, what are you actually disconnecting? If you have disconnected anything while the engine is running you could have damaged the alternator.

[Tony Brooks]

I don't understand

1 minute ago, Tracy D'arth said:

Beta engine?

 

Check the multi plugs and sockets on the engine loom to control panel, there may be two pairs.

 

This ^^^^

 

The only thing  can think that would give you a high charging voltage on the top diagram is if a field diode has failed in the alternator UNLESS it has been changed for a battery sensed one and in that case it may be a problem on the sense lead.

 

I can see nothing on the diagrams that would allow the lower diagram alternator to charge the top diagram batteries so I don't understand the gradually rising voltage unless the battery is warming up by engine heat.

 

Sorry, maybe one for @nicknorman or @Sir Nibble

[ditchcrawler]

It looks as if one is battery sensed and one machine sensed

[Ewan123]

32 minutes ago, David Mack said:

If those diagrams are correct then you have two separate systems, and so the port alternator charges just the starter and BT batteries, and the starboard just the domestic.

 

When you say the port + is disconnected, what are you actually disconnecting? If you have disconnected anything while the engine is running you could have damaged the alternator.

That was my initial understanding.

 

Disconnected the big red cable which I'm sure always was attached to the +ve. Only disconnected while the engine is off, did accidentally short between the alternator and starter motor when trying to connect the alternator +ve (forgot to isolate domestic batteries...)

 

I've updated with more photos and an earth cable that should maybe be attached to stbd alternator??

38 minutes ago, Tracy D'arth said:

Beta engine?

 

Check the multi plugs and sockets on the engine loom to control panel, there may be two pairs.

Isuzu engine, all multiplugs etc. seemed alright (recently cleaned out etc.) but I will check that tomorrow, thanks. 

Edited February 12, 2022 by Ewan123

[MtB]

42 minutes ago, Ewan123 said:

When the + is connected on the Port alternator, the starter battery voltage goes crazy (15V at idle, jumps up and down above that if engine revved higher and the engine also responds to the jumping voltage).

 

How are you measuring this please?

 

Hopefully a digital multimeter with probes on the battery terminals. Any other way and you are probably making assumptions about the true battery voltage!

 

 

[Tony Brooks]

Photos show a standard A127 with the standard regulator adaption for an external alternator controller. Nothing special but  when the controller is dealing with the regulation it is battery sensed so look at the sense wire. However we don't know about the alternator internal wirirng modifications, so the alternator's own regulator might have been disabled permanently. If it has or has not a faulty controller would only give a high charging voltage after a period of charging or well charged batteries. I still favor a failed field diode. But I still can't work out about that 13V gradually rising with the B+ disconnected.

 

That A127 looks like an earth return one to me and as long as both battery banks have a good connection to the engine block and hull that earth wire was probably left over from a previous insulated return alternator. f you are 100% sure it is an earth wire the fix it to an alternator mounting bolt.

Edited February 12, 2022 by Tony Brooks

[Ewan123]

Just now, MtB said:

 

How are you measuring this please?

 

Hopefully a digital multimeter with probes on the battery terminals. Any other way and you are probably making assumptions about the true battery voltage!

 

 

Yes, multimeter direct on the battery (which confirmed what the instrument panel was showing) 😀 I learnt that lesson the last time things went wrong! Also our normal battery monitor panel died in the middle of this mess. 

[Ewan123]

8 minutes ago, Tony Brooks said:

Photos show a standard A127 with the standard regulator adaption for an external alternator controller. Nothing special but  when the controller is dealing with the regulation it is battery sensed so look at the sense wire. However we don't know about the alternator internal wirirng modifications, so the alternator's own regulator might have been disabled permanently. If it has or has not a faulty controller would only give a high charging voltage after a period of charging or well charged batteries. I still favor a failed field diode. But I still can't work out about that 13V gradually rising with the B+ disconnected.

 

I'm trying to think back to the order things happened in... and I remember other things.

 

The first issue was the starter battery going flat and failing to start the engine (I jumped from the domestics twice before replacing starter battery).

 

The Stop button then failed to stop the engine but that's been intermittent for a while. 

 

I also created a brief sparkly short between the Port alternator and engine starter motor when trying to reconnect the big red cable to the +.

 

Is that any more illuminating??

Edited February 12, 2022 by Ewan123

[MtB]

Just now, Ewan123 said:

Yes, multimeter direct on the battery (which confirmed what the instrument panel was showing) 😀 I learnt that lesson the last time things went wrong! Also our normal battery monitor panel died in the middle of this mess. 

 

Thanks. And good! 

 

Looking at your diagram it is hard to image any way your symptoms could happen other than if the alternator is also bunging out the same voltage (or half a volt higher perhaps given your diode splitter). Have you measured the alternator voltage on the + terminal? 

 

(There must actually be more connections to it not shown on the diagram, I think...)

[Tony Brooks]

1 minute ago, Ewan123 said:

 

I'm trying to think back to the order things happened in... and I engender other things.

 

The first issue was the starter battery going flat and failing to start the engine (I jumped from the domestics twice before replacing starter battery).

 

I also created a brief sparkly short between the Port alternator and engine starter motor when trying to reconnect the big red cable to the +.

 

Is that any more illuminating??

 

No, and I don't think the spark as described could do any damage as long as the cable did not catch fire, but I bet it made you jump.

Edited February 12, 2022 by Tony Brooks

[Ewan123]

19 minutes ago, MtB said:

 

Thanks. And good! 

 

Looking at your diagram it is hard to image any way your symptoms could happen other than if the alternator is also bunging out the same voltage (or half a volt higher perhaps given your diode splitter). Have you measured the alternator voltage on the + terminal? 

 

(There must actually be more connections to it not shown on the diagram, I think...)

 

I'll measure that tomorrow too 👍

[Jen-in-Wellies]

1 hour ago, Ewan123 said:

The Stop button then failed to stop the engine but that's been intermittent for a while. 

See the comments on the multi-pin engine plug/socket above. Dodgy connections here will cause this. Can also affect the connections to the alternator warning lights on the control panel, which can prevent, or delay the alternator starting to charge batteries.

[Ewan123]

Thanks all so far.

 

Can anyone advise whether the starboard alternator (last pic) is missing an earth cable? 

 

I'll report back after further investigations into connections etc. tomorrow. 

[Tony Brooks]

2 hours ago, Tony Brooks said:

That A127 looks like an earth return one to me and as long as both battery banks have a good connection to the engine block and hull that earth wire was probably left over from a previous insulated return alternator. f you are 100% sure it is an earth wire the fix it to an alternator mounting bolt.

 

[Ewan123]

Just now, Tony Brooks said:

 

That makes sense, thank you. Yep it's a short wire coming straight from the main earth point. Will do.

[Tony Brooks]

1 minute ago, Ewan123 said:

That makes sense, thank you. Yep it's a short wire coming straight from the main earth point. Will do.

 And I bet it will make no difference.

[Tracy D'arth]

I would check any voltage sensing wire to the controller, we don't know what type it is.

[MtB]

Just now, Tracy D'arth said:

I would check any voltage sensing wire to the controller, we don't know what type it is.

 

There isn't one according to the diagram.

 

I'm now wondering where the diagram came from. Dear OP, did you draw it yourself for the purposes of this thread or did it come with the boat? 

 

[Alan de Enfield]

11 minutes ago, MtB said:

 

There isn't one according to the diagram.

 

I'm now wondering where the diagram came from. Dear OP, did you draw it yourself for the purposes of this thread or did it come with the boat? 

 

 

Maybe it is the wiring diagram as required in the "owners manual"

[MtB]

2 minutes ago, Alan de Enfield said:

 

Maybe it is the wiring diagram as required in the "owners manual"

 

You really think so?

 

Did you actually look at it, in the op?

[Alan de Enfield]

1 minute ago, MtB said:

 

You really think so?

 

Did you actually look at it, in the op?

 

Yes - its much better than some of the stuff I've seen in the RCD owners manuals.

Many of them seem to be a copy / photostat of someone elses boat manual and bears little resemblance to reality. This one looks / sounds as if it does give some idea of what's there

[MtB]

12 minutes ago, Alan de Enfield said:

 

Yes - its much better than some of the stuff I've seen in the RCD owners manuals.

Many of them seem to be a copy / photostat of someone elses boat manual and bears little resemblance to reality. This one looks / sounds as if it does give some idea of what's there

 

So could you see a battery voltage sense wire?

 

I can't, but I have a track record for missing stuff like that.

[ditchcrawler]

3 minutes ago, MtB said:

 

So could you see a battery voltage sense wire?

 

I can't, but I have a track record for missing stuff like that.