Running your Equipment from Batteries

I’m having some work done in my garage. So as a consequence I’ve been forced to go through boxes of things I’ve blown up over the years. Oh, wait; experiments in progress that have yet to be returned to their original state of existence. At least that sounds like someday I’ll do something with all those bits and bobs.  

Going through the piles brings me to my home made Christmas tree lights. Not that the lights are homemade, the battery connection is. My friend plays the saxophone and was marching in a parade; he wanted something unique so I came up with the brilliant idea of mounting Christmas tree lights all over him. The idea was brilliant and the execution was almost as good. The lights went out in the middle of the parade. 

What we had failed to think about was how long the battery was going to be running the lights. We should have done this, next time we’ll do that bla, bla, bla. I need to know who long I can run a string of lights off a battery.

The process for answering the question can be applied to many other useful things. Most recently I have been asked about our TelePrompTers. I need to run it in a corn field. How long will it run from a battery?

Well this is the process that I used (your process may vary.)

AMP Hours /Draw = Run Time

First you’re stuff; how much power will it use.  All consumer electronics have some type of rating for the amount of watts they will require. On our standard monitors the draw is

 35 Watts for a 15 inch monitor,

40 Watts for a 17 inch monitor,

45 Watts for a 19 inch monitor and

50 Watts for a 20 inch monitor. 

Pretty standard stuff, this information is easily found on the back of the monitor, bottom of a plastic reindeer and on the air compressor for the Inflatable Santa. 

Now the battery; Batteries are rated in amp hours, except when they are rated in milliamp hours. Don’t ask me I don’t know either, maybe it looks better to the marketing people to have a bigger number here. But that the great thing about standards, there are so many of them. 

OK, let’s say I have a 14.4 volt brick battery with 95 Amp hour rating (95Ah) or 95 Amp hours for 60 minutes.  

95 * 60=5700 / 35=162 minutes for a 15 inch Monitor

95 * 60=5700 / 40=142 minutes for a 17 inch Monitor

95 * 60=5700 / 45=126 minutes for a 19 inch Monitor

95 * 60=5700 / 50=114 minutes for a 20 inch Monitor 

Now we’’ try a smaller camcorder battery on our LED 128 light. 

The battery is rated at 6800 mAh and the light is rated at 1.8W draw what is the runtime?

6800 mAh or 6.8 Ah or 6.8 * 60  

6.8 * 60=408 / 1.8 = 226 minutes or 3 Hours 46 minutes 

Your mileage may vary, of course this doesn’t take into account other electronic processes going on in the unit or that your battery isn’t pristine perfect from the factory.  But this does give you an idea of what the unit is capable of, and approximately what type of performance can be expected.   

As with any responsible journalist I cannot stress that battery life depends on many factors: battery chemistry, quantity and quality of the load on the battery, number of recharge cycles, and length of non-use, age of the battery and internal design of the battery will all affect how long a batter will last on your particular electronic device.


ValenzuelaKenny Valenzuela has been in television production for almost 25 years working for companies like NASA, ABC, AT&T and C|Net Television.  During that time he has developed a collection of shows from concept to completion for Sci-Fi and Discovery networks as well an ample assortment of commercials.

While his past experiences make him an excellent producer and director, Kenny feels most at home teaching novices how to take their productions to the next level and what to do when bad things happen to good productions.

Currently Kenny is dividing his time between working at Prompter People, Live Nation, and occasionally stepping in to assist with special documentary projects.