Full electrical configuration

david.claassen's picture

Original forum: 

  • Member Discussions:Technical

I am pondering a much needed reconfiguration of my electrics on my 26M. I currently have the usual lights, chart plotter, autopilot, depth, vhf. I will probably install solar "next year".

Mains power....I am seriously considering one of the leads designed for camping that have an RCD, breaker, 3 mains outlets, and a couple of USB's. Simple and more than adequate for my needs.

12 volt (I have one starter and one house battery..both 12v)

Where to relocate my battery selector switch? Mine is cut into the battery cover...horrible place, IMO.

I Breakers vs fuses, or both? I currently have the stock 4 switch box in the original place, plus 3 more in a panel placed in the battery cover.

USB outlets in the cockpit and v-berth?

How sophisticated is your battery gauge?

Any advice would be very welcome.

David Claassen

"Logan's Run"

2006 26M

26 Comments

rick.jones's picture

Hi David

Hi David

Some interesting questions!

I have one of those camping extensions, it's all I've used since I first got a Mac. It's years old (more than 30), I did originally use it for camping, so it's done very well. Too old to have USB built-in though! I now have it mounted on a couple of brackets below the cockpit entrance. Make sure that the mains earth is never connected to any part of the 12V system, otherwise you'll need a galvanic isolator on your plug-in to stop your outboard dissolving. Any good mains battery charger will be fully isolated.

For battery management I very much favour auto cross-charging using a VSR (voltage sensitive relay). Out of sight, automatic, just works.

Breakers are always better than fuses. They trip faster in a fault condition, and can be reset. When a fuse blows you need to find a replacement, and it always seems it's the one you haven't got.

I have several USB outlets. You can find all kinds of configurations on eBay. I like the twin-fitting little panels where you can mix'n'match what goes in them. I like to have a 12V lighter socket plus a dual USB outlet. Make sure the USBs are at least 2.1A, preferably 3A. Many modern devices won't actually charge on less (e.g. 1A of current may be enough to keep the device running, but with nothing spare to charge the battery).

I have a sealed digital panel voltmeter wired directly to the house battery so i have a constant indication of charge level. They're quite cheap (eBay again).

Make sure to use sufficiently heavy gauge wire, you can loose a lot of volts over thin wire. Don't just go on the current rating, wire rated at, say, "1 amp" is so rated on the basis it won't overheat. But at a current of 1A you might loose 1V over a long length. If that's a mains system, 1V loss on a nominal 240V supply is nothing. But 1V loss on a 12V supply is 8% - much more significant.

A useful formula is "mV = 18LC/Q". Or voltage-drop in milli-volts = 18 * metres of wire * amps / sq-mm wire-size. Remembering that's the total amount of wire, so something 2m from the battery is actually 4m wire round-trip. Hope I've not got soo technical there!

Hope that all helps.

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

Hi David,

Hi David,

I agree with Ricks comments - We have a digital electronic relay (Cirex-ct 120A) to ensure the batteries are charged properly and the starter battery is given priority. It also has a override switch so that both batteries can be used in parallel if needed to start the motor. A simple cheap solar panel controller costs about a £10 on ebay and works fine with our 15W flexible solar panel that keeps the batteries toped up. We also wired in a lighter socked with heavy duty wire which is useful for 12 v car accessories - vacuum, polisher and normally has a 2 way USB charger in place.

We have our main isolation switch placed on the end of the port side bunks under the rear end of the sink unit. The wiring is easily accessible from the hatch and with the sink unit in any position. I thought it was a standard fitting but perhaps not. Make sure that if you have a separate automatic bilge pump (we have but have never needed to use it) make sure its wired before the isolator switch if you want it to work when your not on board. No way would I use fuses other than resettable ones from choice on a boat as if the main fuse blows its going to be when you really need it.

A cheap digital LED volt meter with a push button switch set into the battery cover allows routine battery monitoring at the touch of a button. We also have a camping extension lead with RCD but only ever use it with a battery charger occasionally as we have never found the need for 240V on board. We also replaced all the lighting with led bulbs which massively reduces the battery current drain as well as producing a much better quality of lighting.

I think Rick has already mentioned that you need to use tinned copper wire not just copper in a marine environment as copper oxidises - goes black and leads to bad connections.

Hope this helps.

Mike C - Tarka 26M (for sale!)

david.claassen's picture

Thanks to both of you for the

Thanks to both of you for the suggestions. I should have done this bit of work before. My vhf is currently above the forward table settee. The PO had the rotary switch, half of the breakers, the shore power lead and a mains outlet attached to the battery cover. There are at least 6 accessories wired directly to the positive post of the battery. Time to tidy it all up.

David Claassen

"Logan's Run"

2006 26M

john.pompei's picture

Whilst on the subject of

Whilst on the subject of electrics whenever I start the engine it knocks out the Garmin & old Navman chart plotters. I suppose this is due to a voltage change, is there a way to prevent this happening ?

david.claassen's picture

John, 

John,

Are you running only one battery? My instruments all run from the house battery and are (I think) unaffected by the current drain when starting from the starter battery.

David Claassen

"Logan's Run"

2006 26M

I agree fully with Rick's

I agree fully with Rick's love of VSR's and had them on my previous boat where they worked faultessly for 12 years without an issue.

On my new boat I have used a battery to battery charger. There is an issue with newer engines conforming to Euro 5 regs (and maybe Euro 4). Some of these have electronics which reduce the alternator charge while running to reduce emissions. There is a risk (dependent on the actual make and model) that the VSR will rarely kick-in as the flow is too small from the alternator. On RV's, these battery to battery chargers are now standard for exactly this issue.

I also attach a simple guide to wire sizing which may be of use. For most purposes. The 3% drop table is for sensitive and important equipment (eg VHF radio). To repeat Rick's comment, the distance is to AND from the unit.

Kind regards Chris

john.pompei's picture

Hi David,

Hi David,

You have given me a possible answer because I have been a bit careless as to where I set the 3 position switch - actually whilst I have identified which position is which battery I have not checked what is connected to each battery.

It is interesting because in the past I feel sure that starting the engine did not always knock out the instruments so I'll check this out.

On a further point I understand that when the engine is running you must have a battery connected otherwise the alternator may be damaged but should the 3 position switch be in the BOTH position or doesn't it matter ?

By the way I've used a 240V Caravan lead with 3 plug sockets and a circuit breaker and it clips on to the leg of the table which is quite convenient I bought it a few years ago from Go Outdoors and it wis quite cheap below £30 I seem to remember. The lead is a green/yellow sort of a colour about 40' long with a circular three pin plug as used in most marina's I believe.

Hope this helps,

Best Regards,

John

I think it would be a good

I think it would be a good idea if all you guys re-vamping you electrics to make wiring diagrams- so the next owner can figure it out !

david.claassen's picture

Excellent suggestion!

Excellent suggestion!

David Claassen

"Logan's Run"

2006 26M

That's a useful little chart

That's a useful little chart Chris. Personally I try to always wrt on side of heavier duty marine wire which for the short runs we are doing is not expensive compared to general running costs. Sometimes the alliance only has a thin wire but I reckon if I'm extending it then better to go bigger. I have two batteries on my M bothe housed airships in battery boxes having shifted the standard battery across. I find I can just manage to haul them out if necessary through the usual opening under the ladder. One is a dedicated starter battery and the other is for general house functions and the are connected using heavy duty .cables via a VSR but I also connect them through my 1/2/both switch so that can act as an override. Currently all nav equipment lights etc are controlled via reachable switchboard and main positive to that is fed from my 3 way switch plus any other cabin devices /cigar lighters etc. Hence the 3 way switch acts as a selector for which battery drives the house . This year I have realised there are a lot of cables on that switch post and it's hard to get at so I am planing to get a positive terminal post where they can all sit. All my negatives go back to a negative bus bar. This system makes it much simpler if I need to remove either battery.

I use a camping style plug board for shore power and have battery charger, fridge, and a short AC extension lead permanently plugged in ready.

There was a simple on off switch fitted by Macgregor situated at aft end of galley, near port bunk and I route the outboard connection through this so I can isolate it on leaving the boat. This year I have replaced one of my cigar lighter sockets with a dedicated twin usb and have added a socket by the v berth running the cable neatly along port side bilge secured with clips.

Hope that's helpful.

Roly , Aranah. 26M

rick.jones's picture

I'd also like to add a tip

I'd also like to add a tip regarding feeding cable through difficult runs (e.g. in the ceiling or through the bilge space). Once you've fed something through to find the route, pull a piece of strong synthetic cord (so it won't rot) through. Then use that to pull your cable(s) through, and at the same time include another length of cord. Leave this cord in place, with the ends tied off so they don't get lost. Then when you want to thread another cable (almost inevitably!) you've got the cord there ready to use.

And of course if you do use that cord, pull another one through to replace it!

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

david.claassen's picture

Great idea, Rick! I should

Great idea, Rick! I should get started on this plan later in the week, and will keep asking questions until I get it done. Has anybody placed their rotary selector switch directly under the last step of the companionway ladder? That seems to be the easiest solution cable-wise...my theory being that it is a pain to get at regardless...

David Claassen

"Logan's Run"

2006 26M

That's exactly where mine is

That's exactly where mine is Dave and I think also noted same on John Pompeii boat . It's easy to run thick cables to it from batteries but a bit awkward to reach to attach wiring. Ideally best to feed a single cable off the outflow terminal to go to a positive bus bar /fuse board / connection post.

Happy scrabbling!

Roly

john.pompei's picture

Hi David,

Hi David,

Yes, Roly is correct my 3 position switch is under the steps and it seems OK there.

During the lockdown I moved the bilge pump switch next to the 3 way one, before it was next to the other isolator behind the galley and was easy to knock on unintentionally.

Regards,

John

Can anyone tell me how to be

Can anyone tell me how to be sure that my coolbox does not bridge the AC/DC separation as noted by Rick. It is a proper Dometic cooler bought from yacht chandler and the manual says that it automatically cuts out DC once AC switched on. Hence I have both plugged in so that AC will take over once shore power connected. Manual makes no mention of the specific issue.

Roly

rick.jones's picture

Hi Roly

Hi Roly

Do you have a test meter that will measure resistance or continuity? (I.e. the ohms setting)

You need to unplug the coolbox, then measure between the earth pin on the mains plug, and the outer connection on the 12v plug. There should be no continuity (infinite ohms). That's to say no difference in reading between touching the pins and not.

If you get any measurable resistance then the circuits are not isolated.

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

Hi Rick. I do have a meter

Hi Rick. I do have a meter but Im not quite clear. It seems that the plugs will definately be isolated since one comes direct from shore power and one from the battery. Did you mean the sockets in the cool box? Otherwise the only way I could see a connection would be through my charger that is also lugged into the 3 socket camping style cicuit breaker box.

Roly

rick.jones's picture

Hi Roly

Hi Roly

Yes, I mean test the coolbox itself, when it's not plugged in. You're trying to determine if the circuitry in the box bridges the 12V and mains earth. I think it's highly unlikely that it would.

I would expect the charger to be fully isolated.

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

david.claassen's picture

I've started moving things.

I've started moving things. When removing the old shore power lead, I was a bit surprised to see the negative earthed to one of the 12v breaker panels. Is this normal?

David Claassen

"Logan's Run"

2006 26M

rick.jones's picture

Hi David

Hi David

Not sure what you mean by "negative" relating to the shore power lead. Mains has live (brown), neutral (blue), and earth (green/yellow). L & N should never be connected to anything other than 240V equipment. On, for example, a steel hull vessel, earth would be connected to the hull for safety. But this can set up an electrolytic circuit through the water, resulting in corrosion of the boat (which can be severe and fast).

With a GRP hull, there is nothing particular to earth, so there's nothing to be gained by connecting to the 12V circuit. But maybe that's what someone has done? It will create a corrosion problem with the outboard, so best to keep mains and 12V completely separate. If they are kept connected then you should plug shore power via a galvanic isolator.

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

david.claassen's picture

That is exactly what was done

That is exactly what was done. I have removed the connection...it just seemed quite unusual.

David Claassen

"Logan's Run"

2006 26M

rick.jones's picture

Definitely unusual - and

Definitely unusual - and wrong!

Has the boat actually spent much time plugged into shore power and with the outboard leg in the water? If so it's worth checking the sacrificial anodes on the leg, they might have partially dissolved and need replacing.

Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight

david.claassen's picture

Good point....I will!

Good point....I will!

David Claassen

"Logan's Run"

2006 26M

david.claassen's picture

Just back from a few days in

Just back from a few days in Suffolk....brilliant sailing and very happy with the electrics work.

David Claassen

"Logan's Run"

2006 26M

That sounds great David. Very

That sounds great David. Very pleased for you. Where did you venture to ? Any tales to tell?

Roly

david.claassen's picture

Pretty tame stuff...started

Pretty tame stuff...started at Titchmarsh and had two nice, slow sailing days. Then went to Woolverstone, stayed two nights there, sailed back and recovered. No drama at all...mostly 2-3 knot sailing in light air, but I did make 4.5 knots on a nice reach.

David Claassen

"Logan's Run"

2006 26M