Slashdot Mirror
Providing 12V Power to RV-Based Hardware?
jp93023 asks: "I am putting together a mobile computer lab in a converted RV. RVs have a 12v DC system for running most interior lights, built-in appliances, fans and so forth. They have a parallel 120v AC system for providing normal outlets, which is great when you are plugged in. It strikes me that when I am running from battery power (which will be most of the time) I will be expending precious watts converting the 12v from the marine batteries up to 120v, only to convert it right back down to 5, 9, 12, and 20v DC for all the PCs, laptops, etc. The equipment package will include desktops, laptops, digital tape decks, etc., so I'd be planning on bypassing the built-in transformers for everything but the laptops. Have any slashdotters put together a unified low voltage DC power distribution system for such a situation? Would the power savings be worth it? Any pointers to products or plans would be great!"
If battery conservation is important, stay away from the inverter- a large portion of the power will go away as heat- look into switching power supplies, which can run up to 80-90% efficiency. Look through surplus catalogs and so forth, buying them factory new will probably be prohibitively expensive, but they can be quite reasonable in surplus.
Also, try to stay away from linear power supplies- they also will convert a lot of your precious power to heat.
Running a desktop computer off a 12V system looks to be pretty easy at first, especially when you look at the common voltages (+/- 12, 5, 3.3V) But the problem starts when you look at how much current each one of those voltage rails use, it's pretty amazing- 30, 40 amps is not unusual.
With lower voltage DC supplies, you have high currents for the same amount of power delivered, so you're also going to want to use pretty thick wire to distribute the power around. This will minimize the loss of power to the resistance of the wire.
...because this is a project that a lot of amateur radio folk undertake in building emergency communications or stormchaser vans. Most amateur radio equipment runs on 12v DC, and these vehicles also usually pack a number of computers for digital text communications modes, processing weather info and satellite tracking.
Suggested keywords: "communications van", "emergency communications", "stormchaser", "RACES", "ARES"
-=Maggie Leber=-