Re: Power Inverters

On Tue, 06 Jun 2006 00:00:00 +0100, Neil <donotuse@xxxxxxxxxxxx> wrote:

|On Sun, 28 May 2006 20:44:11 +0100, Phil Cook
|<urcamp@xxxxxxxxxxxxxxxxxxxxxxxx> wrote:
|
|<snipped>
|
|>>5(a) = 60(w) ? 12(v) (Assuming 100% efficiency which it's not going to
|>>be)
|>
|>I'm glad you agree with my back of an envolope calculation. Yes 60 W
|>will draw 5 Amps from the car battery. The next thing needed is the
|>size and condition of the battery and how much of the capacity you
|>will need to start the car. If you have a 100AH battery you will
|>probably need 75AH to start the engine so you could run your lights
|>for about five hours. But I would park at the top of a hill, carry
|>jump leads or a tow rope. :-)
|>
|>Something else to consider is the use of a RCD which you may have
|>problems using with an inverter.
|
|Most inverters stop working and just cut out when the battery voltage
|drops below a certain value. This value is usually sufficiently high
|as to ensure that the car battery retains enough power to start the
|car engine(often around 11 or 10.5 volts).

Now that is something I would not bet on, even though I have up to date RAC
membership. *and* I carry a pair of jump leads.

|Residual Current Devices(RCD's) used to be called Earth Leakage
|Circuit Breakers(ELCB's), a term which described their function more
|accurately. Basically this device detects a small current(low
|milliamps) leaking to earth, possibly through a person's body due to a
|faulty appliance, and disconnects the mains voltage from said
|appliance before this leakage current to earth can cause a dangerous
|electric shock to the person.
|
|Since in a temporary or camping situation, it is unlikely that either
|pole of an inverter output will be earthed anyway, there can be no
|leakage to earth to cause a shock, and an appliance with, for example
|faulty insulation can therefore be used without causing an electric
|shock. An RCD in this case would neither work nor in fact be of any
|benefit.

Again I would not bet my life on that. In a tent, in a storm, dirty water
gets everywhere, and one pole or the other will be earthed. An RCD would
work just fine under those conditions.

--
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.

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