New voltage for cars - Ian Cook
Several days ago Stuart B posted an item about a forthcoming changeover to 42 volts (might have been 48 volts). Since then I've been wondering what will happen to caravan and other trailer electrics.

Caravans have quite complex 12 volt systems for lighting, battery charging, and fridges etc. and there are probably other trailers that derive power from the host vehicle.

British cars use the 12N and 12S trailer sockets and the Germans have developed a 13 pin DIN standard, but I wonder what will happen when we have to marry new to old.

I can't see it being as straightforward as putting new bulbs in.

Any body know?
Re: New voltage for cars - Darcy Kitchin

There must be enough expertise in this forum to design "fat" 12N and 12S sockets to step the voltage down. No problemo.

Obviously by then we'll be restricted to travelling during the hours of darkness so correct electrics will be essential.

Anyone know what the 24V recovery vehicles do when connecting up to a 12V caravan?

Now just waiting for the anti-caravanners to start up ...
Re: New voltage for cars - Ian Cook
Oh, I know, Darcy - they will. But it's a serious topic, nonetheless.
Re: New voltage for cars - andy bairsto
This will be introduced over the next few years ,the problem is that there is so much electrical equipment in cars today and more to come 12 volt is not a good transmission medium. I think 24 volt will be favourite allthough most research depts are being pretty flexible on the matter.Caravans will not be a problem as step down transformers are readily available.My brother in laws American mobile home runs at 12, 24, and 220 the main clima and water heating are 220 the vehicle is 24 and the ancillary lighting is 12.
Re: New voltage for cars - Phil P
transformers only work with AC
Re: New voltage for cars - andy bairsto
Rubbish,the voltage of all vehicles today is generated ac then converted to dc, the ac voltage can be converted by diferent means up or down to stay as ac or converted to dc ,as you will see if you study any vehicle wireing diagram .My caravan accepts 12v dc 24v dc and 220 ac all put through one compact voltage convertor.You can convert ac to dc, dc to ac ,modern electronics shows no bounds.
Re: New voltage for cars - Bill Doodson

Just to be a pedant, Phil P is correct, transformers do only work on AC. But Andy you are also correct in that DC and AC can be converted back and forward easily these days with transformers and inverters. Most fork lift trucks work on 48V DC but the newer ones coming through use inverters to bring up the voltage so that smaller AC motors can be used with thinner and hence cheaper wiring. I am looking forward to 48V all round no more 60A fuses, 15A will do just as well etc, but I not sure how its going to affect the bikes, I wait to see.

Re: New voltage for cars - Andy

My two penith,

The new voltage will be 42Volts - not 48. 12V is not a good transmission medium, especially when lots of amps are needed. The major driving force for this is the USA. Their cars use lots of amps, mainly from things like air conditioning.

Secondly, another problem is cold cranking. Cold starting your vehicle in sweeden results in the volts dropping dangerously low (6V). Electronics have to work between typically 6V and 36V. The high limit is to protect if the regulator on the alternator fails.

12V was chosen as traditionally producing cells was expensive/difficult, so only six were needed for 12v.

As to switching between AC and DC - you can do it, but it is inefficient.

If you wanted to convert 12V to 24V DC, you would have to convert it to AC, then put it through a transfomer then convert back to DC.

These DC-DC convertors are expensive and have considerable losses.

Converting downward is not such a problem. 230 ac (we no longer have 240 in UK) just goes through a transformer and rectifier to produce 12V DC.

Dropping 24V DC to 12V DC is a matter of having a regulator with a big heat sink to loose the excess power.

Re: New voltage for cars - steve paterson
What sort of batteries will be needed? To supply 40 odd volts a conventional battery will need about 20 cells. Presumably the battery would have to be three or four times the present size for the same current capacity.
Re: New voltage for cars - Robert
Apparently the new BMW 7 series is the first vehicle to have this system. Apparently the increased battery weight is more than offset by the need to have smaller cabling.
Re: New voltage for cars - Andy Bairsto
This is not quite true the battery is lighter on certain models,plus the use of muliplex wireing has had a tremendous weight saving
Andy's right (Multiplexing) - David Lacey
Multiplexing has reduced the amount (and weight) of the vehicle wiring loom today.

This 12 to 42V change seems to give us the ideal opportunity to dig a huge hole and bury all the bl**dy caravans in, for good.


Snails - Guy Lacey
That's spot on Dave.

As a resident of the South-West of England and a daily commuter on one of the many Holiday Routes (or is that Roots) to the coast I fully support Dave's campaign to rid the roads of these plywood/balsa-wood mobile chicanes.

The number of RTA's caused by snails on the M5/A38, especially around Telegraph Hill at Exeter (Caravan Graveyard) should surely result in the banning of these vehicles during the hours of 04:00-23:30?
Re: Andy's right (Multiplexing) - Ian Cook
No chance - we can always revert to gas!
Re: Andy's right (Multiplexing) - Darcy Kitchin
Just bought a new one ;-)

Value my car