Did I do the math correctly?

[Pirate96]

If you plan on a 26 watt CFL on 120 AC that is the equivalent of a 100 watt incandescent light bulb here is how the math would work out:


26 watt light bulb /120 volts * 10(inverter conversion)= 2.167 amps after the inverter is used. This does not account for the losses of the inverter.


If you went to a 25 watt CFL on 12 V DC that is the equivalent of a 100 watt incandescent light bulb here is how the math works out:


25 watt light bulb/12 volts= 2.083 amps. You can cut it in half by switching to a 24 V DC bulb.


You can switch to the 12 V or 24 V DC CFL Flounder lights and not have the inverter. So our simple system would be a Marine Battery and 2 to 3 CFL Flounder Lights that would run approximately 12-20 hours (http://wokokon.com/cfl-flounder-lights-make-for-a-quiet-evening/) depending on the particular battery you choose.

[HuntingHawk]

The math is right but the comparison may not be right. I've a 120VAC 3watt night night in my storm shelter on commercial power plus a 3watt 12VDC night light off batteries & the 12VDC is brighter.

Ross

[HuntingHawk]

As a comparison, car headlights are 42watts low beam & 55watts high beam.
So 25watts 12VDC you are looking at a very bright light.

Ross

[Pirate96]

As a comparison, car headlights are 42watts low beam & 55watts high beam.
So 25watts 12VDC you are looking at a very bright light.

RossThat will be even better as currently we have 250 watt halogen in the socket. I was surprised at how close the comparison was, but even if the DC used a little more power due to simplicity it would win out.

[Westcliffe01]

Almost all incandescent bulbs have the same filament temperature. The "brightness" is a factor of how large the filament is and the power dissipated. The only exception here is the "rough service" bulbs which run cooler so that the filament can take harder knocks.

When you go to a CFL or any fluorescent bulb, the light emitting surface is the glass surface that has a coating on it. That glass surface is several orders of magnitude larger than an incandescent filament. So subjectively, it does not look nearly as bright, while illuminating a piece of white paper equally well (probably better since the illumination is more even).

Car headlight beams appear brighter of dimmer since the light is directed at the ground on low beam and closer to parallel to the ground on high. So really, the light just isn't entering your eye on low, whereas it does without anything getting on the way when on high.

Making sense ??

When calculating electrical loads, just add up the power of all the items on the AC side then multiply by 1/(inverter efficiency) that gives you the power draw from the battery. Then divide by 12 and you have (near enough) the current draw, but only if your bank is set up to provide 12V. It could just as well be 24V, 36V. 48V or 96V nowadays...

As a comparison, car headlights are 42watts low beam & 55watts high beam.
So 25watts 12VDC you are looking at a very bright light.

Ross

[12vman]

"26 watt light bulb /120 volts * 10(inverter conversion)= 2.167 amps after the inverter is used. This does not account for the losses of the inverter."

"25 watt light bulb/12 volts= 2.083 amps. You can cut it in half by switching to a 24 V DC bulb."

Both statments are true BUT 24 volts is an odd voltage to work with. 24 volt lighting can be difficult to find and you'll use twice the battery to achieve 24 volts..

[Pirate96]

I agree 12Vman in this case 24V makes no sense..... I tried to figure out how the Cold Cathode Lights would work in this situation. I think for one that this is one situation that would not work.


Gotta to keep that one on the shelf for when I get some solar panels to play with.

[12vman]

Mount them in a waterproof fixture and they'll be fine. I have a set that I use in an outdoor light and it's been out there for over 5 yrs. and still works great.

I have 2 sets in my kitchen area that replaced a 40 watt flourescent. 12 watts makes just about as much light as the 40 watt fixture.