On Thu, 10 Dec 2009 12:21:06 -0800 (PST), sid
wrote:

I have a project to decorate the family "Little Red Wagon" with
Christmas lights. So I stated experimenting with LED light strings and
battery combinations. I finally decided to use an Inverter and not
cut up any light strings. The LED light set that I found has 80
lights and the specs state it uses 12 watts. So as a test I connected
two 6v lantern batteries in series and ran the leads to the inverter
(rated at 100watts), connected a lamp with 40 watt bulb.

The inverted started up and seemed to be working, but when I connected
the lamp, the green led on the inverter turned to red and lamp glowed
at 60% of what it should. The voltage from the battery dropped from
12.6 to 11.5v. I need a battery with less internal resistance.

What would make a better 12v source ? Most NiCad drill batteries are
up around 18v+
What is the voltage of battery in APC backups ?
The liitle crap is 12 volts - the bigger stuff 24 and up. Most use
multiple 12 volt batteries. 12v8Ah batteries are common and can be
easily recharged. 12V 5aH batteries are also readilly available.
Often the cheapest way is to by a 12 volt "booster pack" when on sale
at WallMart or wherever. Usually 18 Ah or better, often available for
$49 or less. Come with 110 volt charger and a cord to charge them in
the car from the "convenience outlet" (aka Cig lighter)