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On Thursday 04 September 2008 20:18, Robin Cornelius wrote: > Mark Evans wrote: > > -----BEGIN PGP SIGNED MESSAGE----- > > Hash: SHA1 > > > > Tom Potts wrote: > >> Playing with my Viglen again and after yet another power outage > >> yesterday I was wondering if anyone knows of a very low power (LCD?) > >> monitor that would run of 12v - Black and white would do. > >> The viglen runs of 12v, my router runs of 12v and if I can find a 12v > >> monitor of low power than I can run the whole sheboodle of a car battery > >> connected to a charger. > > > > There are quite a few LCD monitors with external PSUs. Some of these are > > likely to be 12V or less. Though they might want a voltage regulator, > > given that a "12V car battery" can actually be more like 14V. Especially > > with a battery charger connected in parallel. > > > > You'd also want to avoid using a charger which is not designed to be > > used in this way. If you are lucky you will just wind up with a broken > > battery charger. If you are unlucky you will turn the battery into a > > hydrogen gas and spark generator... > > Car batteries are also not designed for deep cycle/long run operations. > They are designed to deliver very high current for short periods of > time. The sealed gel batteries are far more appropriate for battery > powered equipment and can deliver far more energy over longer periods of > time. Car batterys despite having a very high Ah rating will rapidly end > up at a voltage that can cause sulphation of the cells and knacker the > battery permanently. Just to get really pedantic here - total drain will be ~5A@12V on starting up all the equipment. It will run at nearer 2A so it will be a bit like listening to the radio in the car with the engine off*. Power outages are normally two or three hours at most. * not sure about the monitor yet. Gel cell seem to last three or four charges in my experience - they seem to think people who buy rechargeable drills etc only ever put up one shelf or have Homer Simpson for a next door neighbour! And here really should be a law about using invisible ink on receipts! > > An optimum system would use not only a regulator but a switched mode > system that can effeciently convert voltage up or down to the correct > level of 12.0v. Regulators lower the extra voltage by dissipating > current as heat, wasting your stored energy and with many types of not if you do it digitally - used to be about £3 worth of components and 10 minutes soldering if I remember rightly. Not sure how hard it is to get discrete components these days. I love the smell of (now illegal) flux in the morning! Tom te tom te tom -- The Mailing List for the Devon & Cornwall LUG http://mailman.dclug.org.uk/listinfo/list FAQ: http://www.dcglug.org.uk/linux_adm/list-faq.html