Mikes simple project

[mlke03]

I have a fairly simple task at hand. I need to power a 100 watt light bulb by batteries only. I am curious to what kind of battery i need and how much power. Also if at all possible i need this light bulb battery circuit to contain an automatic timer that can turn the bulb on and off every 12 hours. I could use some help. Please be as basic as possible

 

[Russlk]

I suggest you use a 12 volt flourescent lamp. If you use a standard 4 foot flourescent bulb, the light will be more than you would get from a 100 watt incandescent lamp with 1/2 as much power. A battery operated alarm clock would be your timer.

 

[J0HN1]

Hi mlke03,

There aren't many batteries that will supply 100 W,
except of course motor-car starter batteries.

So i am going to assume you mean them.

You can purchase 100 Watt 12volt lamps,
made for motor cars.

They are actually a little more efficient than
higher voltage lamps.

A single motor car battery would run a 100 watt lamp
for about three quarters of an hour before its charge
reduces the output to a mere glow from the lamp.

I reckon you would need five motor car batteries to
light a 100 watt lamp acceptably for twelve hours.

Unless i am mistaken,
and you really mean that you want it to turn on and
off every 12 hours.

Also if at all possible i need this light bulb battery
circuit to contain an automatic timer that can turn the
bulb on and off every 12 hours.

This is of course possible,
a timer could be made to turn it on, and then off again,
it could do that every twelve hours.
But i think you mean the lamp to run for twelve hours,
then to be off for twelve hours.
That would mean your batteries would have to be charging
for the twelve hours the 100 W lamp is off.

If this is for illumination during the hours of darkness
then i suggest using a strip lamp, maybe a 20 or 30 watt
unit would give similar light output. (needs small inverter)
Also consider using a PIR detector, or maybe two, so
that the lighting is only on when needed, then you
might be able to get away with only one car battery.

Most PIR units are low voltage, the mains units usually
have a small 'transformer-less' supply built in, you
could check their working voltage, varies a bit, i have
found some at fifteen volts, and some at nine volts.

The dearer ones often have a light sensor which turns
them off in the daylight, so maybe you could use that.

Best of luck with it, John

 

[J0HN1]

Hi Russ !!

i see you suggest a florrie lamp too.
I'm on dial up, so ive only just seen your post,

John

 

[ante]

Hi, John1

A normal car battery have a capacity from 54 to 70 Ah or if a diesel 70 to 120 Ah. A 100W lamp will consume 100W/12V = 8,33A and after 45 minutes you have used up 6,25 Ah. This means the battery will supply the lamp for a lot longer. But it is just mathematics .

Ante :roll: