Clearly this has to be a common problem for people. What is the run time
with the current laptop battery, its mAh rating, and how much more would
you need to extend that by? Take a look at
http://www.laptop-battery.org/universal-battery.htm
for what is possible that way.
If you really need a lot of Ah's then you may need to follow Simon's advice
and most laptops have a DC-DC converter for using in the car for less
than $100. The harder part is getting another 12V battery and keeping
it charged possibly via Dave's suggestion.
But if you want more portability with wall charged systems with battery,
for example:
http://www.laptop-battery.org/universal-battery.htm
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=1494
which has a 5Ah NiMH battery and does what you need.
http://www.hp-laptop-batteries.com/universal-external-battery.htm
is a 20Ah Li-polymer version for $119
For car battery DC-DC:
http://www.powerstream.com/ADC-Toshiba.htm
Not that I recommend these sites, they were google results
and I would use resellerratings.com to check them out.
Try searching resellerratings site for "external laptop battery"
You might even find a high capacity battery that can be charged
via the laptop and use as a second battery.
WayneS
----
CH is correct. DC-DC switching regulators are in everything, from your
cell phone to your laptop, anything with a battery, even LED flashlights
have them. The LED flashlights even mimic dimming as the battery gets
weaker. There are several types of converters, depending on input/output.
Boost converters are switching regulators that convert lower DC voltage
to higher DC voltage. Buck goes higher to lower, and Buck-Boost can do
both. I have designed many of these in the past. Including one that can run
at 1V input to 3V output, and runs in burst mode when the output current
gets low for low power applications.
Although they do have a "sort of" inverter in them, they run at frequencies of
200kHz to 2MHz, there is usually only a single inductor and no transformers.
Flyback transformers are only used for isolation or high voltage converters.
The higher frequency allows for smaller inductors to be used. They are efficient
when under load. <www.linear.com> can show you hundreds of designs.
There is usually a resistor ratio that sets the output voltage, some even have
an adjustable pot to trim the output voltage.
WayneS
At 03:58 AM 7/16/2009, you wrote:
>DC-DC power invertor is available for a long long time, either up or down
>conversion is possible using switching technology, basically no AC is
>necessary in between.
>
>A good DC-DC invertor can have over 90% efficiency, with the up invertor
>more efficient than down converter usually.
>
>C.H.Ling
>
>----- Original Message -----
>From: "Moose"
>
>
>> Moose wrote:
>>
>> Unless someone has developed a new way to directly increase DC voltage,
>> such a power pack must include an inverter.
>>
>> Whether inverting to a lower AC voltage and converting to DC is more
>> efficient than going up to 110v (here) and back down for DC, I don't know.
>>
>> Moose
>
>--
>_________________________________________________________________
>Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
>Archives: http://lists.thomasclausen.net/mailman/private/olympus/
>Themed Olympus Photo Exhibition: http://www.tope.nl/
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|