Charging A Laptop on 12V?

GordonThree wrote:
Here's a hard pill to swallow. Using the DC to DC converter might actually waste more energy. their designs are likely only be 70% efficient, especially for the cheapest unit you can find on Amazon / eBay.

Good point, GordonThree. That actually is something I've been wondering. I've read several comments on Apple forums where people are saying that their converters can keep their MacBooks operating but do not charge. As far as I've been able to see, I haven't found a vendor that produces Apple converters and is endorsed by Apple. That looks like any Apple converters for sale are grey market and likely to have questionable quality.

I'm curious, though, if someone has had a contrary experience.

The inverter, inefficient it may be is still very convenient and it's one less power brick and cord set to haul around.

How much is the double conversion really costing you? A few watts for a small inverter idle maybe? The laptop off-line converter (ac to dc) is going to be VERY efficient, because of all the red tape out there on such things.

Here's a hard pill to swallow. Using the DC to DC converter might actually waste more energy. their designs are likely only be 70% efficient, especially for the cheapest unit you can find on Amazon / eBay.

The DC to DC converter is a unitasker too, ALL it can do is power a specific laptop. A small inverter is a great multitasker. Space is a premium in an RV of any size, avoid things that only have one (small) purpose.

MacBook Air car charger on eBay for $18.

I once had a friend who, before he went crazy, posited what he called the law of requisite variety: You can live only so long as TOTAL CHOICES is greater than FATAL COICES... Makes sense to me. (the moral is Choice is good by the way)

You have choices

Now I use (normally) A True Sine Wave Inverter to provide 120vac,, Better than power company quality, There is absolutly NO problem using this type of inverter but.. You are correct.. at most it's 90% efficient and the power brick likewise.


I also have used, on occasion a MSW inverter, also at most 90% efficient, but the brick ran much warmer.. Almost "HOT" (Hot is bad Warmer is ok)


I also have a couple of DC/DC c onverters and more coming.. These take 12 (or rather 9 to 16 volts) DC and convert to ... Whatever it says on the power brick for yhour computer (often 19 volts but I've had a few "OTHER" volts) Depending on the DC/DC converter it may have adjustable output voltage, or fixed, and the effiency can be higher than an inverter and is always higher than dual conversion. (they can hit 95% I suspect) I will know more when I get the new buck/boost converters waiting in my mail box next week and have a chance to look at 'em.

WHat I suspect is conversion to high frequency AC.. then back to DC, (high frequency means more than 60 HZ. like 400 or 500).

They make a transformer that goes from 12V DC to 19V DC. I have had one for 10 years or so.

mike-s wrote:
You really should say which laptop(s) you want to power. There are quality DC chargers available. I've used ones from Targus.

Good point! I added that to my initial post. One is a Dell, and it looks like Dell makes an adapter for that model. Mine, however, is a MacBook Air and charges at 14.85 V.

Mike-s, gulf coast, and tenbear got it right. Amazon and eBay have plenty of inexpensive 12VDC -19VDC laptop chargers available.

I have 12v charger for my ACER laptop. AFAIK I bought it at Amazon many years ago. It wasn't expensive but I don't remember the cost. Works fine.

My DELL laptop 12v charger converts the 12v to 19v or whatever, and simply plugs into a cig lighter. I've used it many times over the past 10 years and it works perfect. You don't need to spend lots of $$$ to charge the laptop.

Simply get the correct charger for your laptop from Amazon or eBay... easy.

you can buy whats called a airline/auto adapter for use on airplanes and on 12v auto power. they have a dc to dc upconverter in them. have to get the right plug and voltage. some of them select proper voltage with the laptop plug you enter the model of laptop when ordering it. not real cheep though. easier to get a dedicated small inverter for the laptops they don't draw that much powering a laptop