Tidy up/improve my electrics

[ditchcrawler]

19 hours ago, nicknorman said:

 

I think Brian’s is the relevant point. If LA batteries are well discharged, say down to 50%SoC, then it takes a very long time to properly charge, say 8 hrs or more. This is because the chemicals deep inside the plates have reacted during discharge, and they need to reverse-react to fully charge, which takes time due to their “inaccessibility”.

 

But if a battery is only discharged a bit then no discharge reaction deep within the plates has taken place and so recharging happens quite quickly. The extreme example of this is of course the starter battery which will be fully charged again just a few minutes after starting the engine. We call it “surface charge effect”. But in reality, “surface charge” or “not surface charge” is not a binary thing, it is a sliding scale.

Here are 2 photos, one taken at 4 hours and one at 5 hours

 

[robtheplod]

Now in final (i think!) stages of drawing up how the electrics will all connect on the leisure side of things. I understand that the Solar & Bilge are permitted to connect to the batteries direct (with just master fuse in between) according to BSS. I'm still unsure if the Webasto is also permitted to be unswitched?  Can anyone advise?   Also, am i right in thinking the +ve from the leisure alternator definately needs to be switched as I'm getting different advice on this?

 

Out of interest, is anyone on here a BSS examiner?  Just thinking would be good to run these by them if so?

 

thanks everyone!

[GUMPY]

14 minutes ago, robtheplod said:

Also, am i right in thinking the +ve from the leisure alternator definately needs to be switched as I'm getting different advice on this?

The letter of the bss says via isolator however;

Its a charging source so you could argue that a fuse would be sufficient.

In a two isolator/alternator setup I would not have it via a switch as the chances of running it without it being connected are high.

Edited July 25, 2021 by Loddon

[robtheplod]

11 minutes ago, Loddon said:

The letter of tge bss says via isolator however;

Its a charging source so you could argue that a fuse would be sufficient.

In a two isolator/alternator setup I would not have it via a switch as the chances of running it without it being connected are high.

This is what I'm finding confusing... in my current messy setup the leisure alternator goes direct to the battery terminal with no fuse but I'm a little concerned this has passed due to the examiner not really prepared to trace cables possibly? (understandable!)  Once I tidy things up might this go against me where its obvious where things connect?  Keen to do this once and correctly....

[nicknorman]

The alternator should go via the isolator, no need for a fuse. This is because someone might want to work on the engine / alternator etc and having switched off the isolators it would be reasonable to assume that the B+ fat cable (capable of passing 1000s of amps into a short) would be “cold”.

 

That said, it doesn’t on out boat!

 

No fuse because a fuse blowing out of old age, boredom and thermal fatigue would take out the alternator.

 

[GUMPY]

Just wire it to the batteries but make the cable long enough to go via the switch if it ever gets picked up.

Or have two cables from the fuse one long enough to go to the switch the other long enough for the batteries and swap it out if it gets picked up.

Mine goes to the batteries and has done for 20years on two boats, its never been queried.

[nicknorman]

32 minutes ago, robtheplod said:

Now in final (i think!) stages of drawing up how the electrics will all connect on the leisure side of things. I understand that the Solar & Bilge are permitted to connect to the batteries direct (with just master fuse in between) according to BSS. I'm still unsure if the Webasto is also permitted to be unswitched? 

 The solar and bilge can be connected direct to battery + via a fuse, but that is one fuse per item, appropriately rated for the cabling. I suggest that it’s unlikely that bilge pump wiring and solar wiring are of a similar size, and thus two appropriately rated fuses would be required. Also, you don’t really want a fault with the solar taking out the bilge pump and vice versa.

[Tony Brooks]

3 minutes ago, robtheplod said:

This is what I'm finding confusing... in my current messy setup the leisure alternator goes direct to the battery terminal with no fuse but I'm a little concerned this has passed due to the examiner not really prepared to trace cables possibly? (understandable!)  Once I tidy things up might this go against me where its obvious where things connect?  Keen to do this once and correctly....

 

Connect it to the battery side of the switch but leave enough slack so if an examiner does not like it you can undo a couple of nuts and put the cable where he wants it. What you do after that is up to you.

 

Things are not a bad re running an alternator disconnected, as Loddon's post can be read to suggest. Running a disconnected alternator should do no harm at all - whatever "common knowledge" may tell you. The complete no-no is taking the load off it while it is running. When you do that, it can produce a voltage surge that may not only take the alternator electronics out, but might do the same for some of the onboard equipment. Luckily the batteries ten t damp such surges to a degree and also modern alternators seem fairly good at clamping the voltage to a safe level.

[robtheplod]

Thanks everyone, getting a good picture of the way forward re alternator wiring. What's the consensus re Webasto?

[GUMPY]

1 hour ago, robtheplod said:

Thanks everyone, getting a good picture of the way forward re alternator wiring. What's the consensus re Webasto?

My Eberspacher is fed from a 30amp fuse in the fuseboard  but then I never turn the master switch off  especially not when the Eber is running

 

[nicknorman]

From the BSS list of things that can be connected direct (via a fuse of course)

 

any other equipment where the manufacturer’s instructions indicate or specifically require direct connection to a battery, such as diesel‐fired central heating boilers;

 

If the Webasto is running and someone turns off the battery switch feeding it, it may be damaged and cause local boiling / expulsion of scalding steam and water from the header tank due to no cool-down cycle. Therefore I would not put it through the isolator switch. Read the manual, it probably says the same.

 

Edited July 25, 2021 by nicknorman

[robtheplod]

Thanks again for the replies. I emailed my last BSS examiner just on the off chance of a reply and I surprisingly got one this morning!

 

He said:

 

It is ok for the leisure alternator to connect directly, as it only produces power when the engine is running.

Webasto is ok as well as some have a frost start setting to come on auto when it is freezing.

[ditchcrawler]

16 hours ago, robtheplod said:

    Also, am i right in thinking the +ve from the leisure alternator definately needs to be switched as I'm getting different advice on this?

 

On my boat it does, I like the thought of that length of cable and the bunch of electronics in the end of the alternator  being isolated when I am not there. The only reason I could see for having the Webasto straight to the battery is if it was for frost protection. Personally again I would like it dead when the boat is left.

3 minutes ago, robtheplod said:

Thanks again for the replies. I emailed my last BSS examiner just on the off chance of a reply and I surprisingly got one this morning!

 

He said:

 

It is ok for the leisure alternator to connect directly, as it only produces power when the engine is running.

 

Does the rest of the boat that has to be isolated produce power then? 

[Tony Brooks]

34 minutes ago, robtheplod said:

Thanks again for the replies. I emailed my last BSS examiner just on the off chance of a reply and I surprisingly got one this morning!

 

He said:

 

It is ok for the leisure alternator to connect directly, as it only produces power when the engine is running.

Webasto is ok as well as some have a frost start setting to come on auto when it is freezing.

 

That sounds like more making it up as he goes. That cable, when connected direct to the battery positive, is lime all the time, engine running or not. It is also thick so will carry loads of amps if short-circuited and it will burst into at least loads of smoke if not into flames. If it is in a harness, the other wires will burn as well.

 

If you do this, please make sure the cable is well protected throughout its run so the potential for short circuits is minimised. I am with Loddon on no fuse for the reason he gives.

 

Edited July 26, 2021 by Tony Brooks

[Alan de Enfield]

3 minutes ago, Tony Brooks said:

 

That sounds like more making it up as he goes. That cable, when connected direct to the battery positive, is lime all the time, engine running or not. It is also thick so will carry loads of amps if short-circuited and it will burst into at least loads of smoke if not into flames. If it is in a harness, the other wires will burn as well.

 

If you do this, please make sure the cable is well protected throughout its run so the potential for short circuits is minimised. I am with Loddon on no fuse for the reason he gives.

 

 

Lime = Live ?

 

He sounds a right Lemon !

Maybe the examiner thinks that leccy only flows one way down the cable, maybe he thinks it has a big diode fitted ?

[robtheplod]

OK this is worrying. A BSS gives his views and they don't appear to be correct?  I think I'm going to go with your views and make it switched/fused. I do wish things were black and white...

[Alan de Enfield]

Just now, robtheplod said:

OK this is worrying. A BSS gives his views and they don't appear to be correct?  I think I'm going to go with your views and make it switched/fused. I do wish things were black and white...

 

 

They are - the problem is that many BSS examiners are colour blind and everything is just a murky 'grey'

[nicknorman]

2 minutes ago, robtheplod said:

OK this is worrying. A BSS gives his views and they don't appear to be correct?  I think I'm going to go with your views and make it switched/fused. I do wish things were black and white...

One can always apply common sense too! I decided not to route the alternator through the isolator for a few reasons:

 

1: the cable run is very short, from the engine stud to the switch is a short straight line not passing near any negative cable or hull structure so no feasible risk of chafing /short circuit

 

2: I found that the 175A max charging current was dropping a bit of voltage across the isolator, not now significant for the Li batteries with my remote sensed regulator but it was for LA with the original regulator.

 

3: If the engine is running and something bad happens on the large runs of wiring serving the boat and/or a bit of equipment, turning off the isolator in a panic would have no effect - the alternator would continue to supply whatever was smoking etc.

[robtheplod]

Maybe I need to make a poll about this! 

[Tony Brooks]

11 minutes ago, robtheplod said:

OK this is worrying. A BSS gives his views and they don't appear to be correct?  I think I'm going to go with your views and make it switched/fused. I do wish things were black and white...

 

The problem is that risks are not black and white. An old, much modified by a bodger, type boat stands a higher risk of short circuits than one that was built to the RCD and has not been modified.

 

Alan has given you chapter a verse re the BSS that your BSS bod should have quoted. Others of us have laid out the risks of wiring via the master switch or direct, and suggested ways of minimising the risks implicit in each method. It is for you to decide and carry out the work needed to minimise the risks.

 

Nick has restated them, and I agree with his views (not that that means much).

Edited July 26, 2021 by Tony Brooks

[robtheplod]

1 hour ago, Tony Brooks said:

 

The problem is that risks are not black and white. An old, much modified by a bodger, type boat stands a higher risk of short circuits than one that was built to the RCD and has not been modified.

 

Alan has given you chapter a verse re the BSS that your BSS bod should have quoted. Others of us have laid out the risks of wiring via the master switch or direct, and suggested ways of minimising the risks implicit in each method. It is for you to decide and carry out the work needed to minimise the risks.

 

Nick has restated them, and I agree with his views (not that that means much).

Thanks for your Sage words Tony, as ever!

[robtheplod]

Hi All

 

Been at the boat this weekend and have put up the boards for the re-arranging electrics, but it got me thinking.... where I've put them is above the batteries, but its very hard to get to that area and they will have isolating switches on them. Thinking out loud is there any reason why i cant put a big board and mount all this on the back of the cabinet/engine bay wall as indicated. My hesitation is the gap between the electrics and the drive belt will be about 6 inches.... too close??  anyone see why this couldn't work??  shame if not at much easier to get at.......

 

thanks!!

 

 

Edited August 1, 2021 by robtheplod

[Jen-in-Wellies]

I don't see why not. Suppose a disintegrating drive belt could cause some damage, but if you replace the belts before they look too tatty, the risk is very low.

I moved the house battery isolation switch, current sensing shunt and megafuse to a similar spot.

Jen

Edited August 1, 2021 by Jen-in-Wellies

[robtheplod]

34 minutes ago, Jen-in-Wellies said:

I don't see why not. Suppose a disintegrating drive belt could cause some damage, but if you replace the belts before they look too tatty, the risk is very low.

I moved the house battery isolation switch, current sensing shunt and megafuse to a similar spot.

Jen

thats all very neat and clean Jen! - I've got something to aim for now!!!

[David Mack]

The BSS requires that battery isolators are located "as close as practicable to the batteries", but then goes on to note "accessibility takes precedence over proximity to the batteries", so I guess it depends just how (in)accessible your current location is.