On Wed, 27 Jan 2010 11:49:49 -0700 Michael Torrie <torr...@gmail.com> wrote:
> Charles Curley wrote: > >> Anyone know of a good PORTABLE AC power source? Something like a > >> UPS or something, but smaller. It doesn't have to be big, just > >> enough to power a couple of external devices to my laptop. > > > > Simplest solution: an inverter. Get one specifically designed for > > solid state electronics, e.g. laptops, etc. It must produce a sine > > wave, and if the salesman doesn't know what a sine wave it, it > > doesn't. For what you are doing, a 140 watt inverter is fine. My > > Lenovo R51 is rated for 70 watts and actually draws around 40. > > Of course converting DC to AC back to DC is convenient, but not > efficient. If his portable hard drive is 12 V (many are these days), > then maybe he could run it directly off his car electrics with a > regulator. Hmmm, it might work. He wants 12V DC, nicely filtered and very quiet. The car's alternator provides 14.7 volts nominally. So nominally a regulator should be able to handle the conversion. Depending on the state of the battery and other factors the voltage could be anywhere from 8 to 15 volts, and very noisy. I for one would not care to chance it. (I once started a marine diesel engine with a nearly exhausted battery. The ship's voltage went down to 8 volts, but the engine started.) You are correct that it is inefficient. Buying a new external drive or laptop every so often would be even less efficient. > > I've used el-cheapo inverters for years (probably square wave instead > of a nice sine) and they seem to work fine, although they induce some > noise in my computer's audio. A ferrite choke helps that though. OK. How well do the batteries charge? I'd also be concerned with electrical noise. I may well be over-protective here, but I've learned to spec out equipment for applications where the nearest land was over a mile away. Straight down. I spec conservatively. -- Charles Curley /"\ ASCII Ribbon Campaign Looking for fine software \ / Respect for open standards and/or writing? X No HTML/RTF in email http://www.charlescurley.com / \ No M$ Word docs in email Key fingerprint = CE5C 6645 A45A 64E4 94C0 809C FFF6 4C48 4ECD DFDB /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
