Full electrical configuration

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david.claassen
david.claassen's picture
Full electrical configuration

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

rick.jones
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) 1994 Mac 19 "White Lightning", Isle of Wight

mike.clarke
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
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
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
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

chris.harnan
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
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

david.phillips
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
david.claassen's picture
Excellent suggestion!

Excellent suggestion!

David Claassen

"Logan's Run"

2006 26M

roly.simpson
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

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