Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!van-bc!ubc-cs!alberta!mts.ucs.UAlberta.CA!David_Halliwell From: userDHAL@mts.ucs.UAlberta.CA (David Halliwell) Newsgroups: comp.sys.laptops Subject: Re: Can Laptops be powered from Car Batteries? Message-ID: Date: 22 May 91 06:28:13 GMT References: <18820001@hpspdra.spd.HP.COM> <18820003@hpspdra.spd.HP.COM> Organization: MTS Univ of Alberta Lines: 56 In article <18820003@hpspdra.spd.HP.COM>, tomm@hpspdra.spd.HP.COM (Tom Menten) writes: >|In article cpetterb@glacier.sim.es.com (Cary Petterborg) writes: >|> >|>I saw in a magazine (or catalog) a converter which you could plug into >|>a car cigarette lighter and get 110V AC out. Anyone else know about >|>... >|> >|The thing you're talking about is a "voltage inverter" - Radio Shack has >|been selling these things for years, as have any electronics supply companies. >|All it is (basically) is a transformer that steps 12V to 110V with a few >|rectifiers and assorted filters. > > Well, this weekend, I heard the "voltage inverter" (12DC to 110AC) > described as a preferred solution, allowing all sorts of things to > be plugged in. Then I spoke with a technical support person for one > of the mail order laptop companies who pointed out some problems: > apparently the inverters (at least some of them, presumably including > the less expensive variety most of us would consider purchasing) cause > a radio frequency "hash" that could cause problems for some plugged in > appliances, and also for nearby electronics (especially boat electronics!) > He was much more comfortable with generating systems than inverters. > One consideration in looking at "cheap" inverters is the type of waveform output. I believe that some generate a square wave instead of a sine wave. (This at least used to be true for uninterruptable power supplies from some manufacturers.) If so, you may want to confirm that your laptop will be happy with a square wave output. All this discussion has been oriented toward provision of 110V AC power. I assume that the laptop in question requires AC power and does not run off a battery. For people with battery-powered laptops, check the voltage level provided by the battery. If it is a 12V system, then you can hook it up to a car battery directly. All you need is a cable that plugs into your DC input (likely where the charger attaches) and has clips to hook up to the battery terminal. Make sure the polarity is correct! I have run my Zenith this way for hours, with the battery hooked up to a solar panel for recharging. (AC power was 5 miles away, across a river, with only a footpath for access. Can you say "3 hour cruise"?) For non-12V systems, you may want to be careful. 12V may be all right if applied to a charging connection (the charger MUST put out more volts than the nominal battery rating to charge it), but if a DC connector is hooked directly to the computer guts, a high voltage may fry it. You would then need a DC-DC step-down transformer. These are easy to find (e.g Radio Shack) if you need less than 500-800 mA, but if you need more then it can be a bit tough. Does anyone else have success or failure stories about running computers off solar panels or other alternate DC sources for long periods of time? Dave Halliwell