If you want to build or buy a 12v DC to [some other DC voltage] converter for every machine you might use at the range that is great. But you’re missing the point. The DC to DC converter is an extra cord you have to build or buy. The multi-voltage, multi end-plug DC converter to which you linked is “is OBSOLETE and no longer available.” The same company makes DC to DC converters for particular laptops and those converters (with one end plug design) START at $48.00 and some are over $100.00. See: http://www.powerstream.com/dc-3318.htm

The inverter gives you one universal fitting for about $22 that can be used with any device that has an AC cord. The other factor to consider is, with inverter-supplied AC output from the vehicle, you can use an ordinary outdoor extension cord to run power 20′ or more to the bench.

We really DO understand that, from an engineering standpoint, a DC to DC converter makes more sense than converting from 12v car battery to AC then back to DC. But the inverter lets you use the charging/power cord that comes with the machine.

If you want to go out and purchase or fabricate a DC to DC converter for each machine you may want to operate from the car battery, that’s fine.

DC curent to DC

Similar to this one
http://www.powerstream.com/dc-3318.htm

We KNOW that most devices run on DC. Read my last comment. The problem is simply that the power cord that comes with the machine is set up to use 110-120 Volt AC at the plug end. Yes if you were to cut off the cord, remove the internal transformer circuit and set up a step-down DC-DC circuit to deliver what the machine runs internally, you could do it. But you might have to create a different step down to give the right DC voltage for each machine you have — some 3V, some 5V, some 6V, some 9V. With the inverter you can run any machine that comes with an AC power cord.

Is it intelligent to go from DC (in car) to AC (from inverter) back to DC (device internals)? NO, but unless you create your own custom cord for each device, plugging in to an inverter is simple.

I understand what you’re saying though. I’ve got someone working right now on trying to run a PVM chronograph from the DC USB ports on my laptop, rather than using AC power. Problem is that the USB ports deliver 5V and the chrono needs 12v, so I still need a transformer.

Most items that like a laptop, digital scale, or a ChargeMaster work from DC power. Just like I described above. Both the Chargemaster and its scale work on DC power. Yes the have a power cord that plugs into a wall, which has a transformer that plugs into the wall. It is the black square thing that plugs in the wall that gets warm, and has a cord running out of it. Same concept as a AC cell phone charger. If you have ever taken a cell phone car charger a part you will see resisters inside. All this does is drop the voltage from the cigarette lighter from 12 volts DC to whatever voltage that required to charge your cell phone most likely around 3v DC. The Chargemasters input it 110 to 120 input with an output of 9v DC. A better source of power would be to get an cigarette lighter adapter the steps down the 12v DC to 9vDC to power the Chargemaster. Doing the you would not be able to use the power cord that comes with the Chargemaster

The main purpose of the inverter, in this situation, is not to charge the laptop — though that is one possible function. A Chargemaster requires 110-120 volt AC power, likewise many other devices, though they may run on DC internally, are set up to draw AC current through their power ports/cords. Yes you could have a step-down DC transformer that would give you 5v or 6v DC for your computer, but most laptops are NOT set up to handle DC power sources in (unless you were to get a custom charging cord or you were to remove the battery and try to jury rig something).

What the inverter does is let your car replace an AC outlet if the range doesn’t have one. That lets you run any device which normally “plugs into the wall socket”.

If you look on your laptop power cable and fine the block that has a power cord running in one side and out the other side. Take a look at the writing on the back of it. You will see INPUT POWER 100v –240v AC / OUTPUT 20v DC.

You will have better luck just getting a car charger for you computer