/ Camper question: ac to dc conversion

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woolsack - on 24 Dec 2012
A quick electrical question: if I transform mains 240 volt AC to 12 volts AC, if I then want to rectify this to end up with 12 volt DC does the rectification always involve a voltage drop? What is the best way to do the AC to DC conversion.

It's to give us the same 12 volt DC lighting from mains hookup in a camper electrical installation
Hairy Pete on 24 Dec 2012
In reply to woolsack:
> A quick electrical question: if I transform mains 240 volt AC to 12 volts AC, if I then want to rectify this to end up with 12 volt DC does the rectification always involve a voltage drop? What is the best way to do the AC to DC conversion.

Yes. Every conversion involves some loss. The best way of converting mains to 12V DC would be to use a switching power supply. If you're thinking of using a transformer you need to be aware that 240 and 12V are the RMS value of the AC voltage. You'll get sqrt(2) x 12V as the peak value. Also, 50Hz transformers are much heavier than the transformers used for high-frequency switching - something to take into consideration if you intend to transport the thing.
Cheese Monkey - on 24 Dec 2012
In reply to woolsack: Run it off your leisure battery connected to a mains charger that runs when on hookup. Much simpler and keeps your battery full. Just an idea, not sure how it would work but I think probably much easier.
beth on 24 Dec 2012
In reply to Cheese Monkey: That's how most camper's are wired. Mine is.
Led lighting also takes very little power so less need for hook up.
damo5000 - on 24 Dec 2012
In reply to woolsack:

Just a get a PMS unit, couple hundred quid, controls everything and gives you breakers for your 240v stuff. Works well I've used them loads
needvert on 24 Dec 2012
In reply to Hairy Pete:
> (In reply to woolsack)
> [...]
>
> Yes. Every conversion involves some loss.

Not sure I agree. He asked will there always be a voltage drop. Agreed on every conversion will have waste *energy*, but his output doesn't inherently have to be of some lower voltage.

> The best way of converting mains to 12V DC would be to use a switching power supply.

Agreed!
yeti on 24 Dec 2012
In reply to woolsack:

lights don't care if it's ac or dc so long as it's only lights...
Hairy Pete on 24 Dec 2012
In reply to needvert:
> (In reply to Hairy Pete)
> [...]
>
> Not sure I agree. He asked will there always be a voltage drop.

True. Perhaps I was assuming too much about the nature of the question.

needvert on 24 Dec 2012
In reply to yeti:

Incandescent lights, you mean.
woolsack - on 24 Dec 2012
In reply to woolsack: Thanks for the replies. The battery charger kills two birds so that will be my choice. I will have a look at PSMs
Cuthbert on 24 Dec 2012
In reply to woolsack:

Not sure how you could only step down to 12AC as most inverters will produce DC if going to 12V.

The best way to use 240V to provide power for your 12V system is to have a mains hook up>into van>consumer unit with RCDs>smart charger such as the CTEK 7.0>leisure battery.

This way you will just be charging the 12 system through the hook up. To then get usable 240V you could connect an inverter to the 12V circuit to produce mains voltage or have a spur from your consumer unit to a socket which only takes supply from the consumer unit. This way you can still use your 12v circuit without a hook up, charging from alternator, and also when it is hooked up to mains voltage.
Cuthbert on 24 Dec 2012
In reply to damo5000:

Total rip off though. You can do it much cheaper and better by using a combination of smart chargers and consumer units etc.
Hairy Pete on 25 Dec 2012
In reply to Saor Alba:
> (In reply to woolsack)
>
> Not sure how you could only step down to 12AC

Pah! Youth of today ... no idea!
Once-upon-a-time, a simple transformer would have been used - none of your fancy, la-di-da, modern inverter bollocks. Hook-up electricity! Pah! Last time I ventured into camping it involved scouring the countryside to find a late opening shop that sold the appropriate mantles to fit those newfangled gas lights. Electricity, pah! Luxury!
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Cuthbert on 25 Dec 2012
In reply to Hairy Pete:

Aye but like the Whillans Harness and any Talbot Campervan, they were crap!

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