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MG Midget and Sprite Technical - Mains Power from Car Battery

Hi,

So I was wondering how possible/easy it would be to run electrical products that normally run from the mains off of an extra car battery?
For example, I know a friend said that I could run high-quality mains powered speakers off of an extra car battery in the boot?

Lastly, please don't get the impression I want to 'chav up' my gorgeous car; I really don't. I'm just checking out the options!

Thanks everyone!
Josh 'Midget Mad' Spooner

In my first car ( a metro) I had large speakers in the back from a hi-fi setup. They were passive though, with just the two little wires, rather than directly mains powered. Different impedance as well so were quieter, but the radio had a front back balance so that was OK.

for mains powered stuff you'd need an inverter as far as I know :)
Rob Armstrong

Hi Josh

Without getting too technical it is possible to convert 12volts DC to 230Volts AC but is IMO totally inpracticle.

The issue is not one of voltage or amps but is simply one of power or in other words the ability to do work.

As an example there is hardly enough power stored in your battery to boil a kettle of water but would work if the engine was running with an alternator not perhaps a dynamo.

Speakers on the otherhand do not need to be mains powered anyway. Plenty of high powered ICE designed specifically for cars, just make sure you don run the system too long with the engine off.
Robert (Bob) Midget Turbo

You would use an inverter for this. 12V DC input 240V AC output. They produce a 'modified sine wave' output which some mains powered equipment do not like. What they should really call it is a modified square wave! Pure sine wave inverters are available but they are much more expensive.

They also draw a lot of current from the battery. For example a 1kW device may draw approx 4 amps at 240V, but this equates to 80 amps at 12V. Assuming 100% efficiency of the inverter which won't happen. Probably more like 80%. So you need a big battery or keep it charging which means paying attention to your charging device.

They're ok for charging your laptop or portable drill though.
Steve Church

You would need an inverter to convert the DC battery power to AC, to power the mains speakers, and possibly a feed from the alternator/dynamo (or a split charge system that caravans use to keep an auxiliary battery charged) to keep your second battery charged up.

A bit complicated really!

Here is an example of a Maplin inverter:

http://www.maplin.co.uk/300w-dc-12v-to-ac-230v-power-invertor-48723

Maybe someone else has a better way of doing it...

Sorry, many others have contributed while I was writing this, so forget my ramblings...
JB Anderson

Surely 'mains powered' speakers don't actually need mains power? I would guess that they are only mains powered in order to be convenient for home use and probably step the voltage down and convert to DC.

I'm only guessing, though!
Dave O'Neill 2

Having spent proportionally as much on "hi-fi" as cars I've no idea of what you want and what your mate means

Others here will be able to tell you the technical details - but I'm at a loss as I suspect is your mate

Most "home" speakers are "powered" by the amplifier some have built-in amplifiers (like subs)

With a Spridget the music comes from the exhaust, carbs, tappets, gearbox and back axle - plus of course everything you hear and smell with the roof down
Nigel Atkins

Amen Nigel.
Richard Reeves

Nige
Sadly with a turbo the exhaust note tends to lose it's "RASP" and ROAR

However AC/DC Deep Purple or Blondie? at max output does tend to make up the shortfall.
Bob Turbo Midget England

I'm not a big fan of ICE in classics but I must admit when I had a '74 Rover P6 a few years ago it had already fitted a period radio with MW and LW and listening to music from that period on the MW classic pop station did seem right and took me back to when I was a kid

but what I'd forgotten was the lack of amplifer power, the radio wandering off station and the hissing and whistling

Whilst looking to buy the P6 I did go to see a very little used original car with an original radio that had a period booster amplifer and second (mono) speaker, that did go very loud

My wife always has music playing in her car so for the sake of long boring journeys in the GT6 I bought a NOS period radio and NOS deluxe 3w! speaker, the radio's only about 2w output and the car exhaust was so loud you couldn't hear the radio when on the move

Deep Purple and the like would find me driving faster

The few long boring journeys we both do in my wife's car we've fell into the habit of listening to Jeff Wayne's War of the Worlds
Nigel Atkins

Josh,

If you want speakers in your midget, I'd suggest just going for whatever in-car amplifier and speakers you can afford. There are stacks of good amps on eBay - there are plenty of Chavs out there convinced that an extra 500 Watts will make them more attractive to women and hence it's worth ditching the already-ridiculously-overpowered one they have.

You can fix it in the boot where it will be secure and simply run a headphone jack socket from a convenient spot in the car, where you can connect an MP3 player of your choice.

Has the advantage of not leaving an expensive head-end in the car and making it a theft target and maintaining an original look.

I've not done this in the Midget, but have done this type of setup in a couple of minis.

I work in audio-visual, and there are many spectacularly good self-powered studio monitors available, but they would be completely ruined by the dirty power from the inverter and you wouldn't be able to appreciate them above the racket your car is making anyway.

Do what i've done; spend the money on a pair of decent in-ear headphones which you can wear if you want tunes while you're driving, and will be useful out of the car too!
MarkH1

This thread was discussed between 16/03/2011 and 25/03/2011

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