Ron Dippold <rdippold@cancun.qualcomm.com> (06/04/91)
On the subject of cellular modems and laptops, I've run into something that others might have encountered a fix for. It seems the high-powered laptops such as the Toshiba 5200 don't have any provision for running off of a 12-V DC input. I can imagine that your typical low-power 12-V input might be insufficient to run something like this, with a hard drive, 16 megs of memory, 25 MHz 386, VGA screen, etc. However, we need something that powerful (and we need the slots). Seeing as how a car battery can provide a substantial amount of power, I was wondering if anyone knew of any product that would allow us to run something like this off of the car's lighter jack, or even to hook directly to the battery if necessary. Or of any portable with that much power and a slot that you can take along with your cellular phone. Standard disclaimer applies, you legalistic hacks. | Ron Dippold
Dave Platt <dplatt@ntg.com> (06/04/91)
In article <telecom11.420.10@eecs.nwu.edu> is written: > On the subject of cellular modems and laptops, I've run into something > that others might have encountered a fix for. It seems the > high-powered laptops such as the Toshiba 5200 don't have any provision > for running off of a 12-V DC input. I can imagine that your typical > low-power 12-V input might be insufficient to run something like this, > with a hard drive, 16 megs of memory, 25 MHz 386, VGA screen, etc. > However, we need something that powerful (and we need the slots). > Seeing as how a car battery can provide a substantial amount of power, > I was wondering if anyone knew of any product that would allow us to > run something like this off of the car's lighter jack, or even to hook > directly to the battery if necessary. Or of any portable with that > much power and a slot that you can take along with your cellular > phone. There may be a very real, defensive reason (or two) for the lack of a +12 VDC power input. [1] Most of the "guts" of a laptop or cellular modem probably run on +5 volts. To be able to accept +12, one would need either a linear voltage regulator (which would dissipate, as heat, more than half of the power fed into it), or a switching regulator (which would add size, weight, and cost). [2] 12-volt power drawn from a car's electrical system is hazardous. If the engine is running, the accessory voltage is likely to be quite "dirty", with sags and spikes and high-frequency noise from the ignition, other loads cutting in and out, etc. The auto environment is considered to be "electrically hostile"... audio amplifiers, CD players, etc. which are designed to operate in this environment must include a good deal of overvoltage/spike suppression, etc. The CMOS components in a laptop are quite vulnerable to spikes and surges. If you want to run a laptop, cellular, etc. from an auto's electrical system, you'll probably have to buy an external high-amperage 12-volt- to-5-volt stepdown regulator (probably a switcher, with extensive surge protection and some big filter capacitors), and a "cheater" which will let you plug the regulator's output into the laptop's charger input or directly to the battery-compartment contacts. I'd suggest that you check your insurance and warranty, as well ... it'd be a shame if a spike from the ignition fried your laptop. If you were thinking of running your laptop from the car's battery, with the ignition off: be advised that most auto batteries are not intended for deep discharge. They're designed to provide large amounts of current in short bursts, and to be recharged immediately and kept "topped up" by the alternator. A "low maintenance" or "no maintenance" auto battery can be ruined by only a few deep-discharge/recharge cycles ... it will lose its ability to hold a charge. If you really want to run your high-amperage laptop from an external battery, you'll probably want to get something along the lines of a deep-discharge lead/acid battery, such as are often sold for marine or RV applications. These batteries are designed to be able to be discharged most of the way to zero, and then recharged fully, a large number of times (the tradeoff being that they don't have the same peak-current output as a lead/acid battery designed for automotive use). You could charge this battery from an auto's alternator, or with a standalone battery charger. - Dave Platt VOICE: (415) 813-8917 Domain: dplatt@ntg.com UUCP: ...apple!ntg!dplatt USNAIL: New Technologies Group Inc. 2468 Embarcardero Way, Palo Alto CA 94303
"Patton M. Turner" <pturner@eng.auburn.edu> (06/05/91)
> high-powered laptops such as the Toshiba 5200 don't have any provision > for running off of a 12-V DC input. I can imagine that your typical > low-power 12-V input might be insufficient to run something like this, > with a hard drive, 16 megs of memory, 25 MHz 386, VGA screen, etc. > However, we need something that powerful (and we need the slots). > Seeing as how a car battery can provide a substantial amount of power, > I was wondering if anyone knew of any product that would allow us to > run something like this off of the car's lighter jack, or even to hook > directly to the battery if necessary. In addition to an inverter, which will generate a square wave with the same RMS voltage as AC line current at up to several thousand watts, there is another solution: the Adapata80 and 30. These do not produce AC current, and only work with switching type power supplies. The adaptors produce 80 and 30 watts respectivly, and weigh about 1 pound. They include a cigrette lighter plug for the DC and a 110 volt receptacle for the output to the computer These adaptors being upstream of the power supply should avoid "noise problems" from the car's electrical system. One of these adaptors is being used by the Agricultural Engineering department here at Auburn, I'll check with them regarding their experience with it. The company's address is: Product R&D Corporation 1194 Pacific St. Suite 201 San Luis Obispo, CA 93401 I hope this helps, I'll E-mail any aditional information. Patton Turner KB4GRZ pturner@eng.auburn.edu
John_Richard_Bruni@cup.portal.com (06/06/91)
Aw c'mon guys, deep cycle batteries for laptops??? And warnings about running laptops off 12 volt 'hostile' environments. Any decent chip designed to convert DC-to-DC should handle this, and to h... with the power loss. We're talking *CAR* batteries running laptops for gosh sakes, not C cells running Honolulu Light & Power. Just do it!
Joshua_Putnam <josh@happym.wa.com> (06/07/91)
In <telecom11.424.5@eecs.nwu.edu> dplatt@ntg.com (Dave Platt) writes: > In article <telecom11.420.10@eecs.nwu.edu> is written: >> Seeing as how a car battery can provide a substantial amount of power, >> I was wondering if anyone knew of any product that would allow us to >> run something like this off of the car's lighter jack, or even to hook >> directly to the battery if necessary. Or of any portable with that >> much power and a slot that you can take along with your cellular >> phone. > If you want to run a laptop, cellular, etc. from an auto's electrical > system, you'll probably have to buy an external high-amperage 12-volt- > to-5-volt stepdown regulator (probably a switcher, with extensive > surge protection and some big filter capacitors), and a "cheater" > which will let you plug the regulator's output into the laptop's > charger input or directly to the battery-compartment contacts. A power inverter (like the guts of a UPS) will turn your 12v DC into 120v AC, letting you use your standard AC adapter. Not very efficient having so many power conversions, but probably one of the simplest to plug together. You could use it in a car, or with a separate 12v battery pack. You'd probably want to be sure the inverter produces a regulated sine-wave output considering the fluctuations in the car's electrical system. Some of the cheaper inverters produce noisy square wave power with no regulation or filtering. I don't think I'd want to run my computer on that. I can't recall the brand name, but I've seen lots of ads lately for a fairly compact 100 watt inverter that plugs straight into the lighter socket of a car. For any load larger than that, I wouldn't want to trust the car's standard wiring. If you always drive the same car, just install a 500 watt inverter and put a 120v outlet in your glove box. :) Watch out for dead batteries, though. Joshua_Putnam@happym.wa.com Happy Man Corp. 206/463-9399 x102 4410 SW Pt. Robinson Rd., Vashon Island, WA 98070-7399 fax x108 E-mail: patty@happym.wa.com
Dave Levenson <dave@westmark.westmark.com> (06/08/91)
In article <telecom11.424.5@eecs.nwu.edu>, dplatt@ntg.com (Dave Platt) writes: [ regarding the use of lap-top computers and cellular phones from an automobile 12-volt electrical system] > If you want to run a laptop, cellular, etc. from an auto's electrical > system, you'll probably have to buy an external high-amperage 12-volt- > to-5-volt stepdown regulator (probably a switcher, with extensive > surge protection and some big filter capacitors)... Perhaps I'm confused, but I thought that most cellular phones are designed specifically for operation from an automobile electrical system! Mine certainly is! On the subject of operating computers in cars, you might want to check out TrippLite and others who make inverters. These devices take 12-volt DC and deliver 120 volts AC. They are used on boats and in motor homes to operate small household appliances. Some inverter power supplies are clean enough to operate computers. Dave Levenson Internet: dave@westmark.com Westmark, Inc. UUCP: {uunet | rutgers | att}!westmark!dave Warren, NJ, USA AT&T Mail: !westmark!dave Voice: 908 647 0900 Fax: 908 647 6857