12V power

[RollingFoggy]

Good afternoon,

 

Just a quick question.

As most electrical stuff on the boat uses 12V, I'm guessing its is not directly from the alternator as it would give out 14/15 Vdc for battery charging. Do you need a 10-20Vdc to 12Vdc transformer to stabalise the voltage so you don't blow the head off of all your 12v appliances ?

 

Cheers.

[Alan de Enfield]

No, just run everything using the battery.

 

Some things like 12v TV's are voltage sensitive and such are supplied with their dedicated stabilised power supply.

Edited January 28, 2020 by Alan de Enfield

[dmr]

It can go up to 16v or so if you have a fancy charger/alternator controller that does equalisation charging.

 

There is NO stabilisation, almost all 12v devices (designed for automotive use) will be ok with the higher voltage. If you use cheapo eBay LEDS or a domestic TV intended to work off exactly 12 volts then they may well fail.  12 volt stabilisers are available for individual sensitive devices but are not normally fitted into the boats 12 volt system.

 

...............Dave

[RollingFoggy]

2 minutes ago, Alan de Enfield said:

No, just run everything using the battery.

Thank you,

By that i'm guessing a 12v tvbilge pump or fridge will sit quite happily supping at 14.8V from the battery bank.

That makes things ohh so very easy and simple.

1 minute ago, dmr said:

It can go up to 16v or so if you have a fancy charger/alternator controller that does equalisation charging.

 

There is NO stabilisation, almost all 12v devices (designed for automotive use) will be ok with the higher voltage. If you use cheapo eBay LEDS or a domestic TV intended to work off exactly 12 volts then they may well fail.  12 volt stabilisers are available for individual sensitive devices but are not normally fitted into the boats 12 volt system.

 

...............Dave

Thank you Dave

[dmr]

Some devices aimed at the boating (and maybe truck) market are able to work of 12 volts or 24 volts without adjustment. This includes most LEDs and "proper" 12 volt fridges.

 

............Dave

[Jen-in-Wellies]

10 minutes ago, RollingFoggy said:

By that i'm guessing a 12v tvbilge pump or fridge will sit quite happily supping at 14.8V from the battery bank.

You guess right for bilge pump and fridge. TV; maybe yes, maybe no. Depends. If it is one designed to run off a nominal 12V, like those made by Cello for the caravan, vehicle and boat market, then no problem. Ones that have a 12V input socket from a supplied mains power brick may not cope with the fluctuating voltage and spikes from a boats nominal 12V supply.

10 minutes ago, RollingFoggy said:

That makes things ohh so very easy and simple.

It certainly does.

Welcome to the forum by the way.

 

Jen

Edited January 28, 2020 by Jen-in-Wellies

[RollingFoggy]

7 minutes ago, dmr said:

Some devices aimed at the boating (and maybe truck) market are able to work of 12 volts or 24 volts without adjustment. This includes most LEDs and "proper" 12 volt fridges.

 

............Dave

So automotive and marine stuff is fine then.

I'll be installing one fairly sensitive land based 12v appliance but I have a bespoke dc/dc stabiliser rated for the current draw fof this one device.

As long as i don't need to make a stabilised 12v ring main rated for the current draw of all the appliances it makes things very simple. 

2 minutes ago, Jen-in-Wellies said:

You guess right for bilge pump and fridge. TV; maybe yes, maybe no. Depends. If it is one designed to run off a nominal 12V, like those made by Cello for the caravan, vehicle and boat market, then no problem. Ones that have a 12V input socket from a supplied mains power brick may not cope with the fluctuating voltage and spikes from a boats nominal 12V supply.

It certainly does.

Welcome to the forum by the way.

 

Jen

Thank you Jen.

 

I'll try not to cause too much trouble, but i'm not making promises mind. ?

Edited January 28, 2020 by RollingFoggy

[Alan de Enfield]

4 minutes ago, RollingFoggy said:

As long as i don't need to make a stabilised 12v ring main rated for the current draw of all the appliances it makes things very simple. 

If you do make a stabilised 12v ring main then make sure you use 'huge' cables, the problem on boats is not current carrying capability, but Volt drop.

You could easily start out with 12v and end up with 10v at the other end of the boat.

 

I had that problem with a fridge that was only about 9 feet from the battery, it would not work unless the engine was running. The 'qualified' electrician who had done the wiring had used the correct wiring for the current, but it was far, far too small when volt drop is taken into account.

I ended up using 8.5mm2 cable and it worked perfectly.

[RollingFoggy]

8 minutes ago, Alan de Enfield said:

If you do make a stabilised 12v ring main then make sure you use 'huge' cables, the problem on boats is not current carrying capability, but Volt drop.

You could easily start out with 12v and end up with 10v at the other end of the boat.

 

I had that problem with a fridge that was only about 9 feet from the battery, it would not work unless the engine was running. The 'qualified' electrician who had done the wiring had used the correct wiring for the current, but it was far, far too small when volt drop is taken into account.

I ended up using 8.5mm2 cable and it worked perfectly.

Very true, I had a similar incident after running a 240v supply 55 meters down the garden to the summer house.

Installed a proper distribution board for lights and a couple of sockets , one for the chicken rottissery on the BBQ. When I was checking it out with the meter some of the voltages had fell out into the grass somewhere, I spent the afternoon rounding the little blighters up and putting them into a bigger cable.

Edited January 28, 2020 by RollingFoggy

[Alan de Enfield]

2 minutes ago, RollingFoggy said:

When I was checking it out with the meter some of the voltages had fell out into the grass somewhere, I spent the afternoon rounding the little blighters up and putting them into a bigger cable.