Boat wiring - will this work?

[PaulRainbow]

A quick rummage around the garage has turned up 2 lengths (1 x 3.4m and 1 x 1.7m) of what looks to be tinned battery cable of approx 35mm. I've got crimp ends, a hydraulic crimper, a VSR and a new negative post on order.

It's not the full re-wire I wanted to do, but as I'm positive (groan...) that the issue is on the earth side of the circuit, it'll do for now. The 1-B-2 switch will live on for the time being, but if I wire the VSR up and ensure that I switch to domestic as soon as I've started up each time, I should be fine.

12v DC is positive and negative, no Earths

The VSR is a step in the right direction, at least it cuts out the need to fiddle around to get the batteries all charged up. Two ways to do it with the 1-2-B now ;

1. Designate the batteries as "engine start" and "domestics". Start with the engine start, then switch straight over to domestics.
2. Designate the batteries "emergency start" and "batteries". Use the batteries setting for everything, the emergency start does what it says on the tin.

Either way, the VSR will take care of charging all batteries, with no user intervention required.

 

[Balbas]

12v DC is positive and negative, no Earths

Strange, I distinctly remember changing my old LandRover from positive earth to negative earth.

The VSR is a step in the right direction, at least it cuts out the need to fiddle around to get the batteries all charged up. Two ways to do it with the 1-2-B now ;

1. Designate the batteries as "engine start" and "domestics". Start with the engine start, then switch straight over to domestics.
2. Designate the batteries "emergency start" and "batteries". Use the batteries setting for everything, the emergency start does what it says on the tin.

Either way, the VSR will take care of charging all batteries, with no user intervention required.

I see the sense in using the engine battery as the starting battery. At least then if it starts to fail I'll know about it *before* it becomes a massive problem! And yes, given I'm going to be getting stuck into it all, it made sense to bung a Victron VSR in.

 

[Balbas]

I'm pleased to report that I've remade all of the earths and wired in the Victron VSR. All is now working as it should. At the end of this season I'll do a full rewire, cos it's still a complete rats nest.

Thanks for the help all.

 

[PaulRainbow]

I'm pleased to report that I've remade all of the earths and wired in the Victron VSR. All is now working as it should. At the end of this season I'll do a full rewire, cos it's still a complete rats nest.

Thanks for the help all.

Well done, hope you did the negatives as well

 

[Balbas]

And an update. Motor sailed (in light winds) for approx 7 hours this weekend (couple of hours there and 5 back). The VSR is working well, the engine started on demand each and every time and even though we left the fridge on maxi chat the whole night (froze everything, whoops!) the domestic bank had no problems in starting the engine the next morning.

Job jobbed! For the time being anyway, I still intend to sort out rats nest of domestic wiring over the winter.

Thanks for all of the help.

 

[PaulRainbow]

And an update. Motor sailed (in light winds) for approx 7 hours this weekend (couple of hours there and 5 back). The VSR is working well, the engine started on demand each and every time and even though we left the fridge on maxi chat the whole night (froze everything, whoops!) the domestic bank had no problems in starting the engine the next morning.

Job jobbed! For the time being anyway, I still intend to sort out rats nest of domestic wiring over the winter.

Thanks for all of the help.

Thanks for the update, nice to hear it's all working well for you :encouragement:

 

[Balbas]

And an update. Motor sailed (in light winds) for approx 7 hours this weekend (couple of hours there and 5 back). The VSR is working well, the engine started on demand each and every time and even though we left the fridge on maxi chat the whole night (froze everything, whoops!) the domestic bank had no problems in starting the engine the next morning.

Job jobbed! For the time being anyway, I still intend to sort out rats nest of domestic wiring over the winter.

Thanks for all of the help.

And... Now it's not working again... Had the family on board, so no chance to investigate yet (the wife doesn't like me pulling the boat to bits with everyone aboard and boy is rather too keen to be helpful and *always* seems to be in the wrong place...).

Engine battery seems to charge OK - voltage was showing 13.8 volts or so after 4 or so hours motoring, which would seem to be OK. But the Domestics were showing 12.15 when we set off, 12.15 at the end of our 4 hour motor sail and 12.15 when I switched off.

Obviously I need to check all of the connections, but are there any obvious 'gotchas' I need to be aware of? Eg, what is the switching voltage for the charge to flip from engine battery to domestic? Thinking about it now, that sensor wire has to be the first thing to check.

 

[lw395]

And... Now it's not working again... Had the family on board, so no chance to investigate yet (the wife doesn't like me pulling the boat to bits with everyone aboard and boy is rather too keen to be helpful and *always* seems to be in the wrong place...).

Engine battery seems to charge OK - voltage was showing 13.8 volts or so after 4 or so hours motoring, which would seem to be OK. But the Domestics were showing 12.15 when we set off, 12.15 at the end of our 4 hour motor sail and 12.15 when I switched off.

Obviously I need to check all of the connections, but are there any obvious 'gotchas' I need to be aware of? Eg, what is the switching voltage for the charge to flip from engine battery to domestic? Thinking about it now, that sensor wire has to be the first thing to check.

Is that 13.8V at the engine battery with the engine running or stopped?

The VSR is a prime thing to check, along with any fuses in that path between the two batteries.
If that's all sound, then either you have a battery fault dragging the domestics down, or the alternator is not charging or only charging very weakly?

Also check the black wires, AKA earth AKA negative, they should all be at the same voltage so if you can measure a voltage between one and another, there's some explaining to do...

 

[Balbas]

Is that 13.8V at the engine battery with the engine running or stopped?

The VSR is a prime thing to check, along with any fuses in that path between the two batteries.
If that's all sound, then either you have a battery fault dragging the domestics down, or the alternator is not charging or only charging very weakly?

Also check the black wires, AKA earth AKA negative, they should all be at the same voltage so if you can measure a voltage between one and another, there's some explaining to do...

13.8v on the engine battery with the engine running. Which seemed about normal to me. IIRC (I was tired and it was hot), the 'cold' voltage of the battery before we started the engine was itro 12.9-13v, which would again seem to me to be healthy. when we started the voltage went up to about 13.8v. So that suggests to me that the alternator *is* working - although there is another question related to that, see below.

The engine is a Vetus M4.14 - effectively a marinised Mitsubishi small tractor engine. It's a great engine (let down by poor marinisation) but has a low output alternator (40A I think) - I guess in it's tractor use it would have had minimal electrics and everything would have been driven by a PTO or hydraulics (driven off the PTO).

Alternator question - how do I test the diodes? I've got some dodgy wiring on the boat, so when the rev counter stopped working I paid it no serious heed and added it to the list of jobs for the winter - I just guess how many revs I've got on... I'm now wondering if these things are linked and actually the alternator diodes have packed up...

 

[lw395]

I would be looking for my DC clamp ammeter at this point, to check that the alternator is putting out a useful current.
13.8 is too low IMHO, what is the 'make' voltage of your VSR, is it engaging?

 

[Balbas]

I would be looking for my DC clamp ammeter at this point, to check that the alternator is putting out a useful current.
13.8 is too low IMHO, what is the 'make' voltage of your VSR, is it engaging?

I don't have a clamp ammeter. I've just googled them though and suspect that I may have one by the time I next get down to the boat.

The VSR is a Cyrix 120A job.

OK, so what voltages should I be looking at? A quick google suggests anything around 13.7 - 14.5ish volts for charging is OK and that anything between 12.6 & 12.9 volts is normal for a resting battery. So I seem to be within normal parameters on both resting and charging.

As an aside, it is a Yuasa battery, about 18 months old and specced well above the suggested CCA and AH rating for the engine.

 

[lw395]

To charge at a useful rate, the alternator needs to be capable of at least 14.0V, 14.4 is more typical for a lightly loaded modern alternator.
I'd check the documentation for your particular VSR but they typically kick in at about 13.7 to 13.9V.
It looks like yours is not kicking in because it's either not seeing enough volts or there is a fault?

 

[superheat6k]

If you want a decent clamp meter that includes DC amps then this is excellent for £30 (Ebay)

Uni-T UT210E

 

[Balbas]

I may be adding 2+2 and getting 857, but I can't help but think that the rev counter going intermittent and then stopping altogether is linked to the same issue. I'm now wondering whether one of the diode packs has given up.

I need to get back down to the boat and check all the connections and voltage drop etc, but I can't help but think I'll be needing a new alternator. I'll only pull the trigger on that if I eliminate everything else first, but I'm starting to think that may be the issue. Fortunately my local place is pretty sure they have one on the shelf - they just need the part number to double check. They're also looking into whether there's a retrofit option with 50 or even 60A, which would be nice.

Just out of interest if I put a clamp ammeter on the battery cables, what sort of readings should I expect to get? Presumably, although it's rated at 40A, it'll almost never chuck that out?

 

[lw395]

If the current is quite high, let's say 10A at tickover or 20A at crising speed that might excuse or explain the low voltage.
If the current is low, and the volts are low, it looks like an alternator problem.

I assume the alternator charge light is behaving normally? I.e. coming on with the 'ignition' and going out when the engine starts?

 

[Balbas]

If the current is quite high, let's say 10A at tickover or 20A at crising speed that might excuse or explain the low voltage.
If the current is low, and the volts are low, it looks like an alternator problem.

I assume the alternator charge light is behaving normally? I.e. coming on with the 'ignition' and going out when the engine starts?

Ah, got it thanks. From memory if the battery is really discharged then I'll get 12.something volts but lots of amps and then as the battery charges I'll be getting 14.something volts and minimal amps?

Yes, the battery warning caption behaves normally - shines brightly with the engine off and ignition on, and then extinguishes once the engine is running.

 

[Balbas]

I need to get one of those clam ammeters and get down there again. I borrowed an 'all singing, all dancing' battery and charge tester from the engineering officer at work.

I also used my multimeter. Got a charge showing of 14.4 volts on the engine battery at one stage with the multimeter, and was definately charging the domestic side with a reading of 12.9 or so - so I suspect low voltage high current as the bank is completely dead (showing 12.15 volts at rest).

Anyway, the interesting thing is that I suspected my alternator diodes of being goosed, but the clever meter thingy suggests otherwise, showing that the ripple is fine - although voltage does look low... I suspect I've a poor + connection from the cyrix VSR to the domestic battery bank too, which needs further investigation.

Carting the batteries around is a proper PITA, so I *may* opt for a night in a marina at some point next week and charge the batteries up whilst I'm connected to shorepower. Yes its an expensive way of putting charge into the batteries, but I did myself an injury last year lugging batteries around over the guardwires and into the dinghy etc. My back is worth £35 at least, possibly more...