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Starter Battery, cut off switch? Help


Clodi

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Every mooring seems to have an 'expert' who dosn't hesitate to venture their opinion & guidance. Our 'expert' has just informed me that unless I insert a cut-off/ isolation switch between the starter and the starter battery it's now a "certain BSS fail"

Is this true? given the plethora of ridiculous rules and regulations I don't know what to believe but I don't fancy adding any more connections than necessary.

TBH the guy has a nice new shiney boat but, whilst he may be an engineer I don't really think he's much of a boater, more of a caravan on the water type.

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Yep he's correct. To pass the BSS, every boat needs a battery cutoff switch with a sign above the deck, visible if any deck boards/hatches are closed.

 

https://www.boatsafetyscheme.org/requirements-examinations-certification/non-private-boat-standards/part-3-electrical-installations/battery-master-switch/

Edited by cheesegas
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Does this switch have to be on the wire between the starter and the battery? I have a single alternator and do have battery cutoff switch but not one on the cable in question. I actually have 2 cut off switches 1 for the domestice and the other is between the vsr and the starter battery, It's been that way for the last 2 BSS with no problems.

 

Edited by Clodi
to clarify
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31 minutes ago, cheesegas said:

Yep he's correct. To pass the BSS, every boat needs a battery cutoff switch with a sign above the deck, visible if any deck boards/hatches are closed.

 

https://www.boatsafetyscheme.org/requirements-examinations-certification/non-private-boat-standards/part-3-electrical-installations/battery-master-switch/

You are quoting the non-private boat requirements there. That said, the requirements are virtually identical for private boats. See 3.6.1 of https://www.boatsafetyscheme.org/media/299273/bss-examination-checking-procedures-core-private-boat-public-interim-complete-compress.pdf

Edited by David Mack
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The requirement is to be able to isolate ALL the batteries, this can be done with a single switch in the (common) negative, but more usually there would be two, one on the domestic bank, the other on the starter. Don't be tempted by the cheaper ones with red removable keys - particularly for the starter as it has to carry a high current when cranking.

 

springy

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1 minute ago, David Mack said:

You are quoting the non-private boat requirements there. That said the requirements are virtually identical for private boats. See 3.6.1 of https://www.boatsafetyscheme.org/media/299273/bss-examination-checking-procedures-core-private-boat-public-interim-complete-compress.pdf

Ooops. Didn't see that, thanks.

 

 

8 minutes ago, Clodi said:

Does this switch have to be on the wire between the starter and the battery? I have a single alternator and do have battery cutoff switch but not one on the cable in question.

One side of the switch needs to go to battery positive, the other to the engine - starter/alternator/control panel etc. You're allowed some things to go direct to battery bypassing the switch though - solar/bilge pumps/alarms/critical nav stuff but this must be fused seperately.

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1 hour ago, springy said:

The requirement is to be able to isolate ALL the batteries, this can be done with a single switch in the (common) negative, but more usually there would be two, one on the domestic bank, the other on the starter. Don't be tempted by the cheaper ones with red removable keys - particularly for the starter as it has to carry a high current when cranking.

 

springy

Can I ask about the 'common negative'?. My engine is bonded to the hull as shown in the picture, but my domestic side of things is not. There is no continuity between my Domestic busbar and the negative in the picture. Should there be?

PXL_20220119_155629805.jpg

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Yes, provided you are referring to the Domestic negative busbar. However bonding, and being able to isolate the starter are separate things.

 

The BSS requires that all your batteries can be isolated.  This can be done by a switch in each battery positive lead,  which should be close to the relevant battery, or by joining the negatives together at a busbar then connecting one side of  a switch to the busbar  and the other side of the switch to all of the batteries negative terminals.  Again the switch should be close to the batteries.

Bonding is a safety feature.

N

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I understand about the need for the switch to be between the starter + & the starter battery+. The boatyard that fitted the batteries did not do this and I am in the process of changing  things. As I mentioned it's gone though 2 BSS without this. However the negative Busbar on my domestic side of things definitely does not show any continuity when I connect to the hull bonding point as shown in the photo. The batteries do charge OK. I've never really thought about  it as obviously we do not use the hull as negative as in autos & the basic circuits were installed professionally & it is only now I'm able to really go into it. Just lately I have questioned weather the Cyrix VSR is working ok, but that largely was due to the starter battery being 9 years old😁

Should I add a negative lead from the domestic busbar to the hull bonding point? It will be very easy to do & I'm in the process of re-jigging my engine bay anyway.

I must say that I'm quite disappointed at the quality of the work that didn't come cheap, but, at the time my disability stopped me from accessing the engine bay. As they say if you want a job done properly do it yourself.

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If your battery isolators are in the positive you should have a wire connecting the negative terminal of the domestic battery to the negative of the starter battery, and then from there a chunky cable which leads to a terminal on the back of the starter motor, and from there another cable to the earthing point on the engine bed.

Your earthing point has two wires connected to it. Where do these go?

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1is from the engine block to the earthing point then on to the starter negative.

Looking at the workshop manual for my Bukh DV36 the aforementioned attachment on the engine block next to the Jabsco water pump is the neg for the Starter Motor. So the neg from the starter motor runs from the battery to the hull then on to the starter.

 

Edited by Clodi
to clarify
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12 minutes ago, Clodi said:

1is from the engine block to the earthing point then on to the starter negative.

 

I presume that's the negative terminal on the starter battery, rather than a negative terminal on the starter motor body ?

 

Are there any other sizeable negative connections on the engine - for example on the alternator ?

 

springy

Edited by springy
add word motor
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If there really is no continuity between the domestic negative and the hull bond then if a domestic system short to the hulli occurred no fuse would blow and the hull would become live with domestic battery positive. That might have hull corrosion potential.

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4 minutes ago, springy said:

I presume that's the negative terminal on the starter battery, rather than a negative terminal on the starter body ?

 

Are there any other sizeable negative connections on the engine - for example on the alternator ?

 

springy

Yes the starter battery & no there are no other negative connections.

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To reply to Tony, There is definitely NO continuity between the domestic negative & the hull. There will be in the morning mind you. 

As I already mentioned, surprisingly I have had no problems to speak of since I had the batteries and Cyrix installed. The only reason I didn't do the job myself is due to my disability, at the time I was physically unable to carry out the work. I didn't specify the details as I assumed the boatyard was competent. At the same time I had the Trojan Hydrolink system installed & it was the first time they had come across that bit of kit, I wonder if they simply forgot as there is an empty stud on the negative busbar just waiting for an appropriate connection.

I'm reluctant to name and shame as they were doing me a favour and it was a 'Cash in hand' job. I guess you get what you pay for. Thankfully there's no real harm done as I'm certain there has been no domestic short as until recently there has been no domestic circuits due to fitting out.

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If the domestics are being charged by the alternator then there must be continuity between the negative terminal on the domestic bank and the negative terminal on the starter battery. 

 

I don't understand why that would not also show continuity between the negative domestic busbar and the engine block assuming the domestic systems are working.

 

The fact that it starts gives confidence in the large negative conductors between the starter battery negative terminal and the engine block. 

 

springy 

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2 minutes ago, springy said:

If the domestics are being charged by the alternator then there must be continuity between the negative terminal on the domestic bank and the negative terminal on the starter battery. 

Quite. Unless the domestics are charged by a separate alternator with insulated return (I.e. proper marine rather than car type), and the entire domestic system operates as a floating system.  Still doesn't comply with the BSS.

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28 minutes ago, Clodi said:

I wonder if they simply forgot as there is an empty stud on the negative busbar just waiting for an appropriate connection.

 

Depends what you mean by the negative busbar but the normal way is to link the domestic and engine battery negatives, battery terminal to battery terminal by a length of battery cable (25sq mm CCSA minimum). This is what anyone in the future will expect see so if you do something different they may take time working it out.

Edited by Tony Brooks
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I don't understand how you can have a negative busbar connected to the domestic batt negative which is connected to the starter battery negative and then bonded to Hull then apparently have no continuity between bus bar and Hull ? 

 

I'm reading negative bus bar and assuming you mean where all the negatives for the domestic cicuits come back to. You also say that there are no domestics installed yet due to fitting out ? So do any of the domestic circuits work ? 

 

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  • 2 weeks later...

Finally, solved. My 6 Trojan batts, wired for 12v are in 3 purpose made battery boxes. The domestic neg goes to a shunt & then busbar. I moved the batteries out to clean etc and found a battery cable from the neg side of the shunt leading to the starter battery (neg) but instead of being connected it was coiled and tucked away out of site. The only route to the hull/ engine bond was though an 'earth' lead from a cheap Chinese inverter which was installed at the same time. Needless to say all has been rectified now. Surprising enough the cheap inverter still works but has been replaced.

Thank you to everyone who commented.

  • Greenie 3
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