How do I run 12v appliances off the boat's battery?

[Kelpie]

I have one or two appliances that generally run on 12v through an adapter off the mains. Obviously I could bring an invertor aboard and use my existing adapter, but would it be possible to go straight to the boat's existing 12v supply? Do I need some kind of regulator to stop it from receiving too much voltage?

 

[TradewindSailor]

I have one or two appliances that generally run on 12v through an adapter off the mains. Obviously I could bring an invertor aboard and use my existing adapter, but would it be possible to go straight to the boat's existing 12v supply? Do I need some kind of regulator to stop it from receiving too much voltage?

Before I start I am no electronics engineer, but based on my experience:

Your 12 volt supply can vary between 11.8 V and 14.5 V depending on how your regulators are configured. They can also spike down if a heavy load is applied like a refrigerator.

You can buy dc controllers, their cost depends on how much power (watts) they have to regulate.

I probably wouldn't bother too much .... but it does depend on what you are supplying. I remember a dc converter (changing a nominal 12V to 19V) whining when the supplied voltage was too low, but it didn't blow. Bulbs, electric motors are unlikely to be a problem.

If you are charging batteries though, you'll almost certainly need a controlled input.

Whatever you end up doing, you need to make sure the supply has the appropriate sized fuse. The cigarette lighter type sockets may have 15 amp fuses to protect the wiring behind the socket. It does nothing to protect a smaller capacity device plugged into the source.

It would be good to get the above confirmed by someone else more qualified though.

 

[elton]

Any appliance designed to work from the cigar lighter socket of a car will work just the same, and just as reliably from the 12V supply of a boat. You don't need any kind of regulator - the boat's regulator will take care of things when the engine is running. You just need to wire in a fuse and a cigar lighter socket or multisocket to the swiched 12V main supply from the battery. i suggest you use something like this. Chop the plug off and connect it directly to the swiched 12V supply through a 10A inline automotive fuse.

See top right of this photo inside my boat -

 

[SeamanStaines]

I have one or two appliances that generally run on 12v through an adapter off the mains. Obviously I could bring an invertor aboard and use my existing adapter, but would it be possible to go straight to the boat's existing 12v supply? Do I need some kind of regulator to stop it from receiving too much voltage?

This statement provided without any warrenty, actual or implied!!!!

In my experience most electronic equipment has a fairly wide acceptance of voltage and is unlikely to complain about the differences from your battery. Generally, if the voltage is to low it will simply not work and will quite happily accept the 14+V when charging. You wont get a spike higher than that voltage (unless your alternator has gone berserk) anyway.

I have several pieces of consumer equipment on board that where supplied with 12v mains power adapters (My TV is a Teac unit that had a 12v DC supply for example) and they all have worked very happily for years.

I do however usually make sure they are turned off before I start the engines.

 

[Barnacle Bill]

If you go to a radio parts / electronics shop you can buy a device that "steps up" 12V to the voltage of your choice - I have successfully run a laptop from this. In fact they are marketed to people who want to run laptops from their cars. The only danger is setting the output voltage too high and thereby destroying the item you're trying to run.

 

[SAWDOC]

A fused cigarette lighter is sufficient for me to run various 12v items on board such as searchlight , phone charger. and car vac. Just be careful in terms of draw down of your battery charge - you still need to start your engine!