Installing 12v system- advice for someone who can't understand electric

[Greedyheron]

Hi all

Could anyone offer some advice- worded for someone who does not understand electric- about installing a new 12v system please?

There were 2 leisure batteries, a starter battery and one of the red key isolator switch things and a fuse board onboard. We replaced all the wiring in the boat and are putting new 12v lights, pumps etc in.

We have ;

starter battery and 2-3leisure batteries (replacing all batteries as they are very old and may add one- not sure yet)

We are on shore power most of the time and have a ctek charger

Have a battery isolator switch (off,1,1&2,2)

We have a 12 volt circuit breaker panel

 

There will be a couple of things wired straight to batteries- bilge pump comes to mind.

We are ok with the wiring around most of the boat I think but a bit confused at the battery end.

 

 

Questions wise: other people have split charge things for charging batteries from engine- do I need one? How do I know what I need? Does the alternator not charge both sets of batteries anyway?

People seem to have a mega fuse - what is this, do I need it, where does it go?

Anything wired straight to the battery needs it own fuse- correct?

 

We haven't touched the engine wiring so that's all as it was, best leave that be I think as it works. Anything else obvious I haven't mentioned?

 

Thank you!

[nicknorman]

Split charge thingy - not essential with your selector switch, the only thing is you have to remember to isolate the engine battery when you stop the engine (off shore power) and reselect it after starting. Split charge makes the process automatic, good if you are forgetful. Yes in your case the alternator should charge both sets, but only in the 1+2 position (probably, depending on how its wired).

 

A mega fuse is a proprietary name for a high current fuse with beefy connections for fat cable. You may not need one if you don't have heavy consumers like inverters. It would typically go in fat +ve leads from the battery to a heavy consumer to protect the wiring in case of short circuit. Yes, anything wired direct to battery ( eg bilge pump) should be fused in +ve wire near the battery but not such that when it fuses, it could ignite battery gasses.

 

Overall I would suggest that you don't have sufficient knowledge to satisfactorily rewire and get it right first time. Perhaps you should get a marine electrician in to at least give advice on your particular installation?

[Chris Pink]

Questions wise: other people have split charge things for charging batteries from engine- do I need one? How do I know what I need? Does the alternator not charge both sets of batteries anyway?

People seem to have a mega fuse - what is this, do I need it, where does it go?

Anything wired straight to the battery needs it own fuse- correct?

 

 

 

The 0-1-2 switch takes care of the charging. Assuming engine battery on 1. You start the engine on 1 switch to both after it's started. Leave it on both for half and hour then switch it to 2. when you stop the engine leave it on 2 (domestic)

 

If you want an overall fuse it goes between the isolator feed out and the next thing in line.

 

yes, all things connected straight to the batteries need their own fuses, as close as possible to the batteries.

[Greedyheron]

Marvellous thank you and in words I know the meaning of.

There's no chance I'm touching any of the electric things unless someone watches me do it (I have rubber wellys and a special coated screw driver if I have to , usually with much sending of photos of the offending broken bit before I touch it) but it does help to know what I need otherwise I struggle telling anyone what I want doing and then understanding what's there. I should be able to cope with turning a switch- mind you on my old boat I never worked out which was 1 and which was 2- I will write it down this time.

[OldGoldy]

Hi all

Could anyone offer some advice- worded for someone who does not understand electric- about installing a new 12v system please?

 

Some useful theory here:- http://www.tb-training.co.uk

 

There is somewhere here on CWDF, some notes on how best to interlink your batteries by Gibbo

 

Although I have had formal training on low-voltage electrikery (in communications) I have, on occasions, referred to a book called 'The 12-Volt Bible for Boats' but I suspect that there are many variants with this title.

 

You may be able to find a legitimate one via Google.eBay/Amazon, or if your conscience allows, a download from 'elsewhere' on the 'net! (but I recommend you don't download anything that involves using an 'exe' file due to possibilities of malware)

 

Try - http://motoren.ath.cx/Download.php?filename=/_electrical/12volthandbook.pdf (but I don't know if it's legit or not)

 

ETA warning & link

Edited June 11, 2013 by dave69700

[The Bagdad Boatman (waits)]

1: voltage drop. On any long run of wire the voltage can be 12v at the battery and only 11v or less at the other end of the boat. Multistrand wire is used on 12v systems and the thickness is depending on the demands Amps on each length of wire and the length of the run.

2: your starter battery is isolated to prevent it discharging when the leisure batteries are used to power all the different electrical items. You have to reconnect it to the system to start the engine.

3: if you run all the electrics through the fuse systems you can fuse both the neg and pos sides.

4: use different plug design for 12 v and 240v and run a 240v circuit with plenty of plugs from a 240v circuit breaker.

[bigste]

By your own admission you do not understand electric. You should be aware that 12v is well capable of setting your boat on fire. Leave well alone if you don't understand the stuff. If you do carry on why not contact your insurers and tell them you are not up to the job but are doing it anyway. They will probably run a mile. lol

[Chris Pink]

What a pathetic couple of posts;

 

to paraphrase the last: don't worry your pretty head about it dear, get a man to do it.

 

Were you born knowing everything bigste? or did you perhaps have to learn a thing or two along the way?

How would you suggest a boat-owning amateur goes about learning about electrical systems?

 

As for the man with the funky moniker; most of what you have said is wrong, the one piece of correct information is put in a way that confuses me, and I know what you're talking about.

[smileypete]

What a pathetic couple of posts;

 

to paraphrase the last: don't worry your pretty head about it dear, get a man to do it.

 

Were you born knowing everything bigste? or did you perhaps have to learn a thing or two along the way?

How would you suggest a boat-owning amateur goes about learning about electrical systems?

 

As for the man with the funky moniker; most of what you have said is wrong, the one piece of correct information is put in a way that confuses me, and I know what you're talking about.

 

There was a similar request for help about 3 days ago, which to save repeating it I'll just link to the post:

 

http://www.canalworld.net/forums/index.php?showtopic=57391&p=1087686

 

Only thing I'd add is that the BSS requires certain battery and starter circuits to be a minimum of 25mm², and for inland boats there's less of a need to use wire with tinned strands.

 

My advice the OP would be along the same lines, namely draw a wiring diagram as mentioned in the above post and post it up for comments. If it's too much time trouble to for the OP do at least do an initial attempt at some kind of diagram then, well, hmmm.

 

cheers, Pete.

~smpt~

Edited June 11, 2013 by smileypete

[RickH]

Split charge thingy - not essential with your selector switch, the only thing is you have to remember to isolate the engine battery when you stop the engine (off shore power) and reselect it after starting. Split charge makes the process automatic, good if you are forgetful. Yes in your case the alternator should charge both sets, but only in the 1+2 position (probably, depending on how its wired).

 

A mega fuse is a proprietary name for a high current fuse with beefy connections for fat cable. You may not need one if you don't have heavy consumers like inverters. It would typically go in fat +ve leads from the battery to a heavy consumer to protect the wiring in case of short circuit. Yes, anything wired direct to battery ( eg bilge pump) should be fused in +ve wire near the battery but not such that when it fuses, it could ignite battery gasses.

 

Overall I would suggest that you don't have sufficient knowledge to satisfactorily rewire and get it right first time. Perhaps you should get a marine electrician in to at least give advice on your particular installation?

I maybe wrong , but should you not reselect before starting the engine ?

[Chris Pink]

Which does raise the question - Do communication skills play a part in general 12V electrics or simply in getting focussed help?

 

Personally I would expand on your comments on neatness in wiring. Often when asked to sort people's system the first step is to comb the spaghetti. Most of the problems experienced reveal themselves at this stage.

 

I've done a fair amount of stage work and whenever working alongside the BBC three things strike me; one they allocate sufficient people, time and resources, 2nd they are fanatically neat and tidy and 3rd almost all of the times their systems work first time and reliably. It's the connection between these three things that is the most useful thing to bring to a boat electrical system. And consultancy can work a treat if someone is practical to start with.

Edited June 11, 2013 by Chris Pink

[Greedyheron]

The usual half helpful comments half rants then- I'm always prepared to take the flack when I ask a question here. Thank you to those who explained things in a way I can understand or at least tried- really helpful and I now know what we do/ don't need at the battery end. To reassure the rest, I'm neither lazy nor nuts enough to just try it anyway. Given a choice between paying someone else do it and never understanding how things work or asking some questions so I can try and understand I will go for the second. I've been slowly learning for about 4 years and have got to the point that I can do quite a few things around the boat- but not electric, yet.

I have a wiring diagram for most of the boat- it tells me where to run what wire (not sure how to get it off paper and on here) checked by an electrician who has inconveniently gone cruising, he also checked out the 240 system before we plugged anything it to make sure it was safe. However we had a number of decisions still to make so didn't get as far as the battery/charging bit- hence asking here.

[RickH]

As far as Im aware , and please correct me if Im wrong is that switching from position 1 to position 2 on a battery splitter whilst the engine is running may well blow the alternator as at that moment power is not going to either leisure or starter battery

[Chris Pink]

You should always go through both rather than off. Which is why it's a good routine to switch to both after starting and then to domestic after around half an hour ( if it was an easy start)

 

And yes, Nick wrote 'after' when he meant 'before'

Edited June 11, 2013 by Chris Pink

[RickH]

You should always go through both rather than off. Which is why it's a good routine to switch to both after starting and then to domestic after around half an hour ( if it was an easy start)

 

And yes, Nick wrote 'after' when he meant 'before'

Thanks Chris .

[smileypete]

I have a wiring diagram for most of the boat- it tells me where to run what wire (not sure how to get it off paper and on here) checked by an electrician who has inconveniently gone cruising, he also checked out the 240 system before we plugged anything it to make sure it was safe. However we had a number of decisions still to make so didn't get as far as the battery/charging bit- hence asking here.

OK.

 

There's a few books around on 12V boat electrics, try to borrow, beg or buy them, they should have info on typical boat wiring. Also have a look a the course notes on the TB training web site, there's some electrical info there too. Finally a google image search on the right terms may get some helpful info too:

 

https://www.google.co.uk/search?q=1+2+both+battery+switch+wiring+diagram&hl=en-GB&tbm=isch&tbo=u&source=univ&sa=X&ei=hnC3UZH-N-z30gWCjoHoDA&ved=0CDoQsAQ&biw=1018&bih=650

 

cheers, Pete.

~smpt~

Edited June 11, 2013 by smileypete

[nicknorman]

I maybe wrong , but should you not reselect before starting the engine ?

You're probably right, but it depends on how its wired. It might be that the selector switch only affects charging and doesn't disconnect the engine battery from the engine, however more likely it does and so mine was a typo!

[smileypete]

Which does raise the question - Do communication skills play a part in general 12V electrics or simply in getting focussed help?

It most certainly does, if there's not a lot to go on or it comes out in dribs and drabs.

 

I'm always interested to see how willing the OP is to spend their own time and effort to help themselves. Some sort of diagram is a most welcome sign, or even use of the search facility or google. Is this too much to ask?

 

If there's nothing forthcoming maybe the best you can do is offer some blanket advice and advise the OP seeks local help from someone competent and experienced or a marine electrical professional. Is that reasonable?

 

Personally I would expand on your comments on neatness in wiring. Often when asked to sort people's system the first step is to comb the spaghetti. Most of the problems experienced reveal themselves at this stage.

I'll wager the spaghetti almost always comes from doing things in a random ad hoc way. Which is why it's good to have at least some sort of wiring diagram in the first place. Easy to get a neat diagram then do the wiring to match, surely.

 

If the quality of the connections isn't all that good I'd rather rip the spaghetti ball out completely and redo it, reusing what I can. Even just moving the wiring can open up bad connections, and having touched the mess it may be expected you've assumed liability for it working OK.

 

Going back to the OPs question I'd rather wire the alt to directly to the domestics via a big fuse and then use a split charge relay to connect the start batt when the engine is running. The 1-2-both switch would be used to isolate the domestic loads and/or parallel the domestics to the start batt for emergency starting. But there should be some way of isolating the engine electrics, so an extra isolator may be needed there too.

 

cheers, Pete.

~smpt~

Edited June 12, 2013 by smileypete

[WotEver]

3: if you run all the electrics through the fuse systems you can fuse both the neg and pos sides.

Not only is this unecessary it could, under certain circumstances, cause a fire. Never fuse the negative on any circuit on a boat.

 

Tony

[gazza]

As far as Im aware , and please correct me if Im wrong is that switching from position 1 to position 2 on a battery splitter whilst the engine is running may well blow the alternator as at that moment power is not going to either leisure or starter battery

Good quality changeover switchgear should be make before break, meaning no harm will be done to alternator. The only caveat to that is you must not select off position with the engine running.

 

Chris pink and I have both commented on the advantages of this system over automated split charging systems. It's only downfall is it requires a little human intervention to make sure you don't end up with a flat battery. Namely remembering to switch from start to domestic supply, not that difficult really!

[Chris Pink]

I thought about this and decided that the "both" position must be arrived at by a quadrant of copper that overlapped and therefore would always be make before break.

[nicknorman]

I thought about this and decided that the "both" position must be arrived at by a quadrant of copper that overlapped and therefore would always be make before break.

But with frequent use, I wonder if it would eventually wear and cause intermittent contact as it was operated?

[gazza]

But with frequent use, I wonder if it would eventually wear and cause intermittent contact as it was operated?

No, good quality kit lasts an age. Cheap crap red key isolators are a different kettle of fish though.

[WotEver]

Cheap crap red key isolators are a different kettle of fish though.

For a fish kettle though, surely you'd need a wood-burning stove...?