What size fuse for 12v Lighter/Accessory socket?

[gandy]

Hi,

Our boat had a car-type cigarette lighter fitted, but no longer connected or working. I want to get that reinstated, and I am planning to wire it straight from the main battery switch with a separate fuse. I was just wondering what sort of current can be safely drawn from this sort of socket, so that I can size the fuse and wiring correctly.

I was thinking maybe 30A, does that sound about right?

 

[Guest]

[ QUOTE ]
Hi,

Our boat had a car-type cigarette lighter fitted, but no longer connected or working. I want to get that reinstated, and I am planning to wire it straight from the main battery switch with a separate fuse. I was just wondering what sort of current can be safely drawn from this sort of socket, so that I can size the fuse and wiring correctly.

I was thinking maybe 30A, does that sound about right?

[/ QUOTE ]

The Electric cool box at 7A melted the wires going into my socket - when I first bought boat ... Guy who sold boat and box - reckoned he used without trouble. First time out - "What's that smell of burning ?????"

Had to rewire and fit a new socket ... card it came on reckoned up to 10A if I remember ... few years ago now. 30A is a lot ... that's 360W .... without thinking about losses etc. Probably not the socket that would be limiting factor here - but the wires connecting it !
I do occasionally run an inverter of 150W max through mine ... and it is ok ... ...

 

[andy01842]

30amp is defiantly to high I would not go over 15amp cheap sockets 7 amp max. As always the wire should have a higher rating than the fuse as other wise the wire becomes the fuse!

 

[davidpbo]

These sockets were probably only designed for intermittent use. Be conservative with the fuse rating and use the heaviest practical cable 2.5mm minimum. Mine gets warm with the cool box drawing 5 amps for any length of time so whilst I might consider fusing it 15amps if I was going to use it as a lighter, I would make sure the plugs of any appliances were fused at less, ideally around the 5 amp mark. You can get fused pugs for lighter sockets.

 

[VicS]

I agree with suggestions that 30amps is way too high. These auxilliary sockets and plugs do not latch together positively like the cigar lighter does into into the socket in your car. Consequently the contact is poor and can easily overheat if subjected to high loads.

What ever you decide the fuse value MUST be no greater than the rating of the wiring you use to connect it up. Fused plugs should be used if the equipment plugged in has wiring rated less than the value of the circuit fuse.

 

[pappaecho]

The problems with cigar lighter sockets, is that the plugs make little metal to metal contact, and often the positive is unsprung so that it fails to make a proper low resistance contact with the socket.
My 9 amp rubber dinghy inflator, got the socket( a "proper marine one") so hot that the plastic melted. I strongly suggest that you rethink the idea. Cigar sockets are fine for low wattage items such as mobile phone chargers etc, but for higher wattages I would strongly suggest gold plated sockets from Maplin. These take banana plugs in the end, have knobs which unscrew and so will clamp on spade connectors, and at worst case will clamp onto bare wires.
I put a pair on my wheel house and cunningly spaced them accidently so that a 2 pin socket for the vacuum cleaner fits, and so does my Philishave 12 volt razor.
These sockets work fine for the dinghy inflator, and do not get even warm. I still have the fuse set at 15 amps. The only cigar lighter on the boat is set at 4 amps

 

[VicS]

[ QUOTE ]
I would strongly suggest gold plated sockets from Maplin.

[/ QUOTE ] I have been thinking about these, but not necessarily gold plated ones. Have you thought of any way of ensuring that the polarity is not reversed. I know they are colour coded but mishaps can happen! It used to be possible to get small non reversible 2 pin plugs and sockets, probably only rated at 2 amps, maybe 5, but jolly useful nevertheless. They looked quite neat.

I think you are suggesting Maplin N48AQ and N49AQ. The plain 4mm sockets N32AP and N35AP would look neater but are not gold plated and only accept 4mm plugs not spade terminals or bare wires.

Maplin do not quote current ratings for any of these but I notice that the small terminal posts FD69A and FD72P are rated at 15amps and even the 2mm sockets HF44X and HF47B are rated at 10 amps.

 

[webcraft]

Ours was fused 10A when we got the boat and has been blown a couple of times, both times when powering a laptop - once through a dodgy inverter and once through a dodgy 12V-17V 'car' power supply.

So - I reckon 10A is about right and we have stuck with it.

- W

 

[bluedragon]

I've had so many problems with cheap plugs wobbling and losing connection with these sockets that I'm changing over to a proper marine outlet with screw-on retainer for anything critical or high current. As others have said, these are rated at best 10-15A and I don't think I'd risk that much going through anyway.

 

[gandy]

Thanks for the comments. The heavy current things I was thinking of were cool box, and possibly a dinghy inflater (I don't have that at the moment). Both these would need to be able to run off the car as well as from the boat on occasion, so the cigarette lighter plug would be convenient. Chargers and things won't draw much current.

I also have a 300W inverter, but that won't need to be used except on the boat, so it could use any form of plug and socket. Its not a priority to get that set up in any case.

On consideration I think I'll connect up the lighter socket with heavy cable so that it could be changed for a heavy-duty socket in due course, but meantime fuse it at 10A.

 

[Drascomber]

Don't get a car type socket. They rot in no time and you can't latch the plug in. If you can afford it get a Marinco one. Stainless and if you use their plug it will latch which is better for higher currents.

I wouldn't fuse it any higher then the max your dinghy inflator needs and half the currrent your wiring will take.

 

[gandy]

Trouble is that a huge number of devices use the lighter plug as a power source. Using a different format means replacing the plugs on those devices, and also fitting a different accessory socket in the car.

 

[FullCircle]

As a Ford worker bee, I can confirm that NORMAL cigarette lighter sockets are rated at 10amps.
However, if you pop along to your Ford dealer and ask for an Auxilliary Power Socket from a Transit post 2003, it is rated at 20amp and says so on the lid. No need to buy the ciggy thing either, as it hasnt got one, just a closing flip lid. It is of proper manufacture, and not one of the car shop clones which are shoddy and cannot handle high amperages.
We invented the 20amp socket as our customers like BT, British Gas etc were plugging lap top, dash top fans, phone chargers and cool boxes through multi sockets into the single 10a sockets, just like your Granny did to 5 amp sockets at home in the 50s.
Suggest 30a fuse and 6mm cable and good practise would be through a relay to your switching.

Beware the power consumption though - under 3 hours for an 85aH battery at full tilt!

 

[gandy]

Cheers, that sounds ideal. I notice that the Freelander lighter socket is fused at 20A as well. There seems to be some variation!

 

[FullCircle]

In the spirit of cooperation, they will be the same item, as they are the same Company that owns the two brands/models.

 

[gandy]

Right, so whose spares are cheaper, LR or Ford?

 

[FullCircle]

Ahem, Sir I think they may be the same.
I will have a root round tomorrow to see if one can be liberated for training purposes.

 

[Drascomber]

Should have made it clear that the Marinco marine spec 12vLighter/accessory socket accepts normal cigar lighter plugs too.

 

[gandy]

Is this the thing?

http://www.marinemegastore.com/jump/28/cat_id/ECLSHO004/product-product-BUR_187530.htm

 

[Drascomber]

Yep, that's the socket but buy a plug and socket set and then you'll have one plug at least that will stay in - for your most critical accessory - presumably not the dinghy inflator.