Power was out for about three hours today.

Got to looking at my options for getting back online, with least effort.

My netbook would easily have lasted three hours.

And the phoneline was still up and running.

The problem today was the modem. I am on DSL. The modem requires 12v 1a in.

I got online last winter, when BOTH the power and the phone lines were down. How... I have no idea. The power was out, and there was no dialtone on the phone line. But once I had everything running on a generator, the DSL worked flawlessly. I could get online, but I couldn't make a phone call. Go figure...

So, next time, I figure that if I can get the modem powered up, I'll be able to get online for at least as long as the netbook battery lasts.

A car battery puts out 10 to 14 or 15 volts, at a bunch of amps.

I need a way to get from that to a regulated 12 volts and one amp.

Simplest, "buy something" solution, is going to be to get a universal power adaptor meant for a car, and use that.

But I'd like even simpler. Cheaper. Etc. The only real caveat being that of course I do not want to burn up the modem.

Can anyone steer me in the direction of the correct resistors, regulators, diodes, caps, etc... needed, and a crude diagram of how to put them together?

If you've got a car battery handy, an inverter to give you 110ac might be easier. An example:

http://www.amazon.com/inverter-blackber ... y+inverter

You could probably buy or build a voltage regulator, but why? Get an inverter that'll give you 120 VAC to work with. If all you're interested in is your modem, a car battery will probably drive that for a few days on an inverter. Even cheap ones are relatively efficient. I have one on our boat that's not much bigger than a cigarette lighter USB charger to use with a laptop if needed. Not that we really need it any more, we've both got tablets & smart phones, so can just run those straight off of a 5 VDC USB plug into the cigarette socket.

Think about that, guys.

Convert from 12 volts dc, to 120 volts ac. Just so I can plug in a wallwart, and convert back to 12 volts dc...

A big waste of resource. You waste energy going from dc to ac, and then waste more going from ac back to dc.

I just need to regulate whatever semi-predictable voltage I get off of a car battery, into a predictable 12 volts, one amp.

Jeff, Take a look at the Xtend Micro Products,inc line. Check out the model E660.
I use this in my truck, car and when the power is out.
Output Voltage 5.0 to 24VDC
Out power 60 W max
Input voltage 12-16 VDC
Input current 6.5A max
Overload protection 2 fuses
Weight 11.2 oz
Dimensions 1.3" x 2.3" x 4.8'
Complies with RTCDO-160c SECTIONS 18, 19,20,21 and FCC part 15 Class B