LAPTOP BATTERY POWER FROM 75-150Ah ?

It depends on the laptop input requirements. Best bet is to go on line and look for an automotive adapter for your particular laptop.

If you are not running a charger or alternator, the laptop adapter will likely drop out as the battery voltage starts to sag due to discharge. Check the adapter's minimum input voltage. Some are designed to work with a battery floating on an alternator supply and may drop out pretty quickly.

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Paul Hovnanian     mailto:Paul@Hovnanian.com
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Who is General Failure and why is he reading my hard drive?

On a sunny day (Thu, 19 Mar 2009 17:37:12 -0700 (PDT)) it happened datakoll wrote in :

I actually desiged this PIC based solultion for just that:

10 to 15 Volt in, 9 V out

But it would be a lot easier to just buy one of those 12V to 230V DC-AC converters for in the car, as that will work with any laptop adapter, and your shaver too, if you are on the road:

I'm missing here. I'm concerned the 75aH and 2 75aH (150 aH) deep cycle batteries offering way too much dc power for the Dell 1705 laptop at est. 5 amps at 10.38 volts. Thus, a device is necessary between the battery bank and the laptop. The 10.38 voltage is from the standard lithium laptop battery. So a

75aH deep charge should have enough voltage to supply the laptop. My approach was a dc to dc connection saved power over an inverter. Using an inverter btween two dc devices is not logical. a transformer ?

The auto adapter suggested IS a DC/DC converter. Targus makes (OK, has made for them) a few models that take both AC and DC inputs, then supply power to the notebook using a tip that somehow instructs the DC/ DC to provide the proper voltage. My guess is the tips have a resistor to tell the power supply what voltage is required.

As a person that likes to run ham gear in the field, I'd be more inclined to roll my own LDO. These DC/DC make a hell of a lot of RF hash.

I will tell you that I had one Targus fail in the field. It failed quite dramatically, with the tip melting. It got so hot that the notebook power input hasn't been the same since. Unfortunately, there are not a lot of alternatives out there. Kengiston is another company that has these universal supplies built for them. I wish Belkin would get in the business. Not that Belkin makes (OK, has made for them) gear superior to anyone else, but at least Belkin has a lifetime warranty. I've had Belkin crap replaced no questions asked. All you pay is the shipping to the factory.

In theory, you can use an inverter, then the AC/Dc that came with the notebook. This makes even more RF hash. I friend the supply that came with my Fujitsu using an inverter, and I am gun shy about running any electronics on a modified square wave. However, an offline swticher, which just rectified the line voltage as the first step, should not care that the input is a crappy modified sine wave. Possibly the peak current in the diodes would be higher, but you would think the designer of the offline switcher would consider the possibility of a square wave being the AC source.

On a sunny day (Fri, 20 Mar 2009 17:34:35 -0700 (PDT)) it happened datakoll wrote in :

The idea is to use the AC adapter that comes with the laptop. The loss of efficiency exists, but it saves you designing and building something, so the solution of a DC-AC converter is cheaper. Whatever you like most.

Ok, you have a 10.38 volt li-ion batt. So why is that your criterion? Surely you don't intend to connect that lithium battery directly to a source of power. You will plug your COMPUTER into some power source. You should concern yourself with the voltage printed on your computer's power supply, or in the computer's owner's manual. Your computer calls for that voltage, and you should supply it with that voltage. Of course, your computer might actually run from a supply that provides several volts less than that. Mine does. I have a Toshiba that runs from a 15 volt power pack but also runs when I connect it directly to a 12 volt lead-acid battery. This computer has a li-ion battery with a voltage similar to yours. If the print on your computer's power supply says 15 volts, you may well be able simply to plug your computer into your RV battery. My Toshiba laptop uses a 15 volt power supply, and when I use it in my truck, I simply plug it into the cigar lighter with a power cord I made (I bought a barrel plug the right size to plug into the back of the computer). The computer runs on anything the truck's electrical system puts out, from 12 to 15 volts, depending on whether I have the engine running. Only disadvantage -- with the engine not running, I can't charge the computer's battery. I have been operating my computer like this for years, I even leave it plugged in when I crank the engine over. It has never done any harm.