[Greenbuilding] DC stored power for Laptoops for grid outages

[LarenCorie]

From: "Eli Talking" <elitalking at rockbridge.net>


> Any experience on the list for running laptops off of low
> voltage direct current batteries?

Hi Eli

    I have two deep cycle batteries (one in the house,
one in my van)  that I use,  to keep my laptop running,
in case of a power outage.       I used to have a DC to
DC converter, but burned it out in my vehicle (they are
expensive and blow if you hit the starter with it plugged
in :O(  So, I now just use an inverter.  If power outages
were common, I might buy another of those converters,
but fornow, a $20 inverter works fine.

>  I checked into UPS and to get a 8 hours at 60 watts,
> the units were over a thousand dollars.

60Watts?  What kind of energy pig of a laptop do you have?
My 17" Toshiba uses less than 20W, through its converter.
The cheap inverter might add 15% to that, but the total
should still be under 25W. With a DC to DC converter
it is likely to be around 15W. 

> Reading the fine print on my power chord AC-DC adapter,
> it list the output at 18 volts, I assume DC. 

Yes....It is powered by its DC battery.

> This could be 3 deep cycle batteries hooked in series that
> could normally kept at full charge with a smart battery
> charger when the grid is proving power.

I choose to not go so fancy.  When my laptop battery
runs down, I simply plug my laptop into my deep cycle
battery, through the inverter (which I otherwise use to
plug into the lighter sockets of my van).     When it is 
charged, I unplug it. A Group 29 deep cycle battery
(under $100 at WalMart) should be able to run the
laptop for close to two day continually, on a full
charge.  Keep it simple.

 -Laren Corie-
 Natural Solar Building Design and
 Solar Heating/Natural Cooling/Energy
 Efficiency Consultation Since 1975
 www.ThermalAttic.com  (many new
 photos and pages, coming soon)

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