12v Basic Circuit.. help needed

[tigglestiger]

Hi All,

This is my first post and i am hoping there is the knowledge out there to help me.

I have a Seafarer 18' Day Sailor which currently has no electrical system on-board.

I want to install a basic system with a cabin light, depth finder and mast light. I have 85 amp battery and i am looking for some help as to what else i need.. can i run dirct from the battery or should install a switch panel?

 

[VicS]

An isolator switch and a main fuse close to the battery would be sensible ( fuse rated to protect the wiring.)

Feeding a simple switch panel with switches & fuses, or circuit breakers, for each circuit.

Remember wiring has to be heavier than you would use for the same current on mains circuits to avoid volts drop., but use heavy-ish wiring for robustness any way.

Consider LED lights to keep power comsumption to a minimum.


Electrical systems tend to grow so allow for that to happen.

How you going to charge the battery?

 

[William_H]

Electrical system

On a small boat you don't need very much. As said it is vital that there be a fuse to protect wiring. All circuits on one fuse is Ok. and you need an isolation switch.
Charging is your biggest concern. If you take the boat home a charger off the mains is the best bet.
If the boat stays on a mooring then a solar panel will keep it charged. Or alternatively you have to take the battery home for charging. If you use an outboard for a lot of time then a charge circuit may help a bit.
Solar panel power depends if the boat is on a swing mooring or is always oriented one direction so panel can be angled to face the sun. I would suggest a 10w would probably suit most people who only sail on weekends. Whatever you do don't let the battery go flat and stay flat that will kill it.
PS fit a VHF radio also as the very best safety bang for your buck. good lcuk olewill

 

[VicS]

PS fit a VHF radio also as the very best safety bang for your buck

I said elecrical systems tend to grow..... begun growing already !

For a day-sailer I'd suggest a hand held VHF would be adequate.

 

[Dipper]

My old Hurley 22 had a pretty basic electric system but it did have the ability to charge the battery.

I am not an electrical expert (as you will see later) but in simple terms you need a battery (tied down securely), an isolator switch and suitably sized cable leading to a simple switch panel with fuses. Any electric items can then be wired into the switch panel.

I had an isolator switch like this. I kept the key attached to my key ring so I couldn't leave the boat without isolating the battery:

An isolator switch of some kind is essential. Before I fitted one I accidentally caused a short circuit in a wire leading to the bicolour light. The short proceeded rapidly along the wire like a fuse with sparks, smoke and flames issuing from it. I had no quick means to isolate the supply and it eventually went 'pop' in the voltage regulator and stopped.

This type of switch panel seems popular (and cheap) although not of the best quality so keep it dry.

 

[tigglestiger]

Thanks everyone.

I have a Raymarine Handheld VHF for safety. It is the 'comfort' i am hoping to improve.

My outboard does have a charging facility - does that connect straight to the battery?

I have seen you can get 'all in one' battery boxes with an isolator switch and 12v socket on them, would this be any good for my needs?

 

[--ice--]

A fuse needs to be put as close to the + side of the battery as possible, then a cut off switch where it is still close to the battery but get-at-able if you need to in a hurry. As pointed out, make sure that the cable is capable of taking all the current loaded when everything is switched on and then fused appropriately, remember, cable has its own resistance therefore the longer the cable the more resistance the lower the voltage at the other end. Over spec the cable, cost a couple of quid more but less hassle and less effort for future proofing!!
Just for your reference, might help with your planning;

21w 12v bulbs draws 1.75 amp
5w 12v bulbs draw .41 amp
I = W / V, where I is Current, W is Watts(power) and V is Voltage

Now all we need are wireless batteries

hth

 

[John100156]

I would definately recommend a battery isolator switch. I would not recommend a single fuse/breaker, otherwise all cabling upstream would need to be sized/rated to carry the current of that rated fuse. A main fuse close to the battery then a small fused switch panel is the preferred option IMO. Just seen ICE post all good advice.

Also note if you are adding a charger or PV array, then you would need to make sure your battery box or enclosure is vented.

 

[Stu Jackson]

There are a number of basic boating electrical resources on the internet, Google is your friend. Draw a wiring diagram first to figure out how it all goes together before you buy anything. Read the engine manual to learn how to connect the engine to the battery.

 

[TQA]

AND PRETTY PLEASE WITH SUGER ON IT

Use different colour wires for the diffferent jobs.

Make a labelled circuit diagram with wiring colours make copies one of which should be laminated and stuck somewhere near the switch panel. .

 

[Barry Jones]

My advice would be to buy a decent battery isolator switch - the cheap ones don't stay the distance and shouldn't be near your engine or fuel tank due to sparks.