JBJ - at full whack they are normally more efficient - with only about 5-10% losses. On that basis it's won't draw more than 15 amps, which is fine so long as the car is running, as a typical alternator is producing 60-70 amps.
The problems can come when you stop, and don't disconnect the inverter, as many cigar lighters are not switched off by the ignition.
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The one I've got, which was not costly, is supposed to be 90% efficient (in:out), and is supposedly OK for things like laptops. It takes 1/2A just to run, & switches off if the "battery voltage" drops below a certain figure. It's quite handy - but, I have wondered about the power output available from the cigarette lighter!
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Yes, don't think the cigar lighter socket is designed to carry more than 3A , from memory.
Also, a 240V supply at the end of a lead ,without RCD protection may have fatal consequences . (Thinks of puddles and camping.)
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" cigar lighter socket is designed to carry more than 3A" yes, you need to check as the fuses are sometimes hidden away from the main panel and a pain to get to. Some sockets also are designed primarily as power outlets, I have two in my boot which say 15A on each.
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without RCD protection may have fatal consequences
As the inverter has no connection to earth (unlike household supplies) an RCD would do nothing (trips on difference between live and neutral current in the cable).
You can happily shove you finger in the "live" pin of an inverter, singing in the bath and nothing would happen.
Now grabbing both connections - that is a diffent and considerably more dangerous matter.
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As the inverter has no connection to earth (unlike household supplies) an RCD would do nothing (trips on difference between live and neutral current in the cable). You can happily shove you finger in the "live" pin of an inverter singing in the bath and nothing would happen. Now grabbing both connections - that is a diffent and considerably more dangerous matter.
Can you explain this further for me, please? Struggling to get my head round it but very interested nonetheless!
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Can you explain this further for me please? Struggling to get my head round it but very interested nonetheless!
to get an electric shock you need a return path. Now as your neutral at home is bonded to an earth somewhere, if you grab the live YOU become the neutral/earth.
With an inverter the neutral is NOT bonded to earth, so if you grab the inverter live you are not providing the return path. grab the neutral pin as well THEN you become the "load" across the mains - a human lightbulb if you like.
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to get an electric shock you need a return path. Now as your neutral at home is bonded to an earth somewhere if you grab the live YOU become the neutral/earth. With an inverter the neutral is NOT bonded to earth so if you grab the inverter live you are not providing the return path. grab the neutral pin as well THEN you become the "load" across the mains - a human lightbulb if you like.
That makes sense AE, thanks - so why do they not use an isolation transformer on houses rather than RCD's? Would that even work? Or would that just be a cost issue?
Thanks!
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That makes sense AE thanks - so why do they not use an isolation transformer on houses rather than RCD's? Would that even work? Or would that just be a cost issue?
Actually there is - but its in that little locked substation at the end of your road. The problem is heat. The car inverter is providing 150 watts and it gets hot. At a peak (with the cooker on and an electric fire or two) you could be consuming 5kw. Thats a lot of heat, the transformer needs to be big, and expensive, and will have losses.
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Actually there is - but its in that little locked substation at the end of your road. The problem is heat. The car inverter is providing 150 watts and it gets hot. At a peak (with the cooker on and an electric fire or two) you could be consuming 5kw. Thats a lot of heat the transformer needs to be big and expensive and will have losses.
Dur, of course forgot about the sub-station! So in theory a house having it's own isolating transformer would be safest? (But utterly unfeasible)
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Dur, of course forgot about the sub-station! So in theory a house having it's own isolating transformer would be safest? (But utterly unfeasible)
In theory you could have an isolating transformer for all the sockets and exclude heavy loads like cookers. ISTR that shaver sockets have small transformers inside. School science labs and the like use them as well AFAIK.
This is similar to the yellow isolation transformers on building sites (and my garage) in addition they stepdown to 110V for reduced shock hazard and the earth is taken from the centre tap of the transformer so in theory the highest voltage is 50V to earth. I thkn the earth only exists to cover possible fault conditions within the transformer itself.
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>> That makes sense AE thanks - so why do they not use an isolation transformer >> on houses rather than RCD's? Actually there is - but its in that little locked substation at the end of your road. .
We have our own transformer, supplying just our (isolated) house. It is on a pole underneath the main cross-country high voltage lines in the next field. Two wires come into the house, and one then branches into Neutral and Earth, so they are in our case the same thing.
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" It takes 1/2A just to run, & switches off if the "battery voltage" drops below a certain figure"
That's pretty good, so I may have been unduly pessimistic. As for the power available from the cigarette lighter, I think they're usually fused at 10 or 15A - cigarette lighters themselves must draw most of that!
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This one was fifteen quid from Aldi a couple of years ago - better and possibly cheaper might be available now.
I are do be have toyed with the idea of mounting the thing in the car somewhere, possibly under the dash, and wiring it in permenantly via a surplus fuse way (it's got an on/off switch on it).
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"I are do be have.."
Is that dialect? :-)
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He's got one in his milk float, it's the fastest in the west
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FT, please may I ask, why DO you need to charge up your toothbrush in the car?:)
Pat
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Yes, we're all agog!
JH
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But it is not illegal to charge it but I'd like to see the police response to using it whilst driving. And does charging show intent?
I am wondering if FT is onto a cost saving here... car produces electricity anyway so why not charge phones, iPod/MP3, toothbrush, sat nav, vacuum cleaner, razor, etc.
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I liked AEs idea of a human light bulb. I suppose if you didn't thrash around on the floor whilst you were dying you would be an 'energy saver'
Ted
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FT is clearly of combined Scottish and Lancastrian stock, and has company-provided petrol. He doubtless has a 12v kettle for his morning cuppa, and charges all his gismos when on the move, and thus saves a good 8p a day on his domestic bill. Over a lifetime of driving and charging he'll save about £700, I calculate.
I'd pick that up in the street, if I found it. But then I'm from Lancashire too.
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It doesn't charge very fast.
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Perhaps it's a hands-free toothbrush.
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"Perhaps it's a hands-free toothbrush."
Perhaps it's a bluetooth-brush?
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to get back to the original :-)
electric toothbrush chargers are typically plugged into 'shaver sockets'
as has already been stated - these contain an isolation transformer - which is limited to 20VA.
If your charger is capable of drawing more power than this, then it will do so from the inverter supply, but will not from the shaver socket.
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My charger unit (Braun 5000) is normally plugges straight into the mains, using an adapter. There's no "limiting" device. The charger doesn't get hot from the mains - it does from the inverter!
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The charger doesn't get hot from the mains - it does from the inverter!
Only cool answer would be:- Get a decent sinewave inverter. Your charger has a transformer that doesn't like square-wave AC.
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Martin123 - which is where we came in! See the second post.
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I know, just restating the obvious.
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Why not ust put the aforementioned teeth in a jam jar, put the lid on with a little cleaning fluid and let the motion of the car clean them ?
Ted
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You cheeky (snip)!
Edited by FotheringtonThomas on 13/03/2009 at 12:29
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