On 08/08/2012 11:04, Vic wrote:
>> The original url showed a 12V to 240V converter.
> The conversation had moved to a PSU that has dual 240VAC or 12VDC inputs.
> The claim was that the 12V input is more efficient. It is not.
Oh I see.
I'd read through the mails a couple of times, but had failed to
recognise that the PSU to which you referred was capable of 12V or 240V
_input_.
The universal PSUs I usually see are, e.g., 12V to 24V input to
user-selectable output voltages.
I think you're right that in the context of your supply, any efficiency
difference will be minimal.
>> It's most likely that the USB output is single conversion, but a laptop
>> or similar would need powering via the 240V
> Not so. This is why I mentioned the 12VDC in laptop supply I was using at
> the time of my posting.
Agreed .. we were discussing different concepts.
I did say I thought there was a misunderstanding :-)
>> So at that rate you'll use half your car's battery capacity in a little
>> under 3 hours, and you really don't want to take a car battery much
>> below that.
> It gets worse than that if you start drawing serious power. A typical
> automotive alternator will develop something in the region of 100A max. My
> large inverter draws >150A...
>
Again my figure was based on the PSU in the url, which is 150W.
150A+ implies 1.5kW. As someone else said, you won't get that from the
lighter socket.
On a typical battery (without the alternator active), you'll also not
want to supply that for longer than a few minutes.
Gordon.
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