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| 12VDC wattage requirement for 120VAC light http://dcaudiodiy.com/phpBB3/viewtopic.php?f=5&t=1625 |
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| Author: | mix4fix [ May 13th, 2020, 11:42 pm ] |
| Post subject: | 12VDC wattage requirement for 120VAC light |
I have a pair of 120V under cabinet plug-in lights. My plan is to use them in my work van since the crappy battery powered ones keep failing down (magnetic) and they break since they are cheap. My plan is to use a bigger power inverter than I normally use, but I am not sure on what size. 400watt? 750watt? |
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| Author: | Roscoe Primrose [ May 13th, 2020, 11:49 pm ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
How many watts are the lights? |
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| Author: | mix4fix [ May 14th, 2020, 2:12 am ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
Bulb: F15T8-WW 15watt each 30watt total. Plan was to use a dedicated power strip to switch them both on or off. Plus a second power strip charge the laptop and charge the portable air blower (Hurricane). |
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| Author: | tomp [ May 14th, 2020, 9:40 am ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
If you only draw 30 watts, this is a cost effective inverter that should have enough spare capacity to work with the fluorescent ballasts and it is quasi sine wave. https://www.harborfreight.com/80-watt-c ... 66944.html |
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| Author: | tomp [ May 14th, 2020, 9:42 am ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
BTW, assuming close to the 87% efficiency claimed, the draw off the battery would be around 3 amps. |
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| Author: | mix4fix [ May 14th, 2020, 2:54 pm ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
Can you break done the math, so I get an idea of what I need to work with? Two lights, laptop brick, wall-wart, and a little bit to spare. |
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| Author: | tomp [ May 14th, 2020, 3:27 pm ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
Steve: First determine the total load in watts of all things you want to power from 12 volts. Then look for an inverter that will take the 12 volts and convert it to 120 volts AC with enough power to cover the loads plus probably a factor of 2. In the case of your two lights that took 30 watt, the 30 X 2 = 60. The inverter I mentioned is rated a continuous 80 watts which should be sufficient. As far as how much current is being drawn by the inverter, take the output power of the inverter and divide it by the efficiency of the inverter. This one was 87% or .87. Divide the 30 watts by .87 to get roughly 35 watts. Divide the 35 watts by 12 to get to the input current or in this case 35 /12 or roughly 3 amps. So the power supply must be able to supply at least 3 amps to run the lights off that inverter. A 5 amp supply would probably be better. If you are using a battery, to see how long the battery charge will last, determine the amp hour rating of the battery at the expected load. Rated amp hours are normally rated at a 20 hour rate. If you were using a 7 amp hour battery, the actual capacity at 3 amps would probably be more like 4.5 amp hours. Dividing the 4.5 by 3 amps to get a run time of 1.5 hours. |
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| Author: | mix4fix [ May 15th, 2020, 11:45 am ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
tomp wrote: If you only draw 30 watts, this is a cost effective inverter that should have enough spare capacity to work with the fluorescent ballasts and it is quasi sine wave. https://www.harborfreight.com/80-watt-c ... 66944.html Any other brands you recommend? |
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| Author: | tomp [ May 15th, 2020, 12:31 pm ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
First make sure you know all the loads you will put on the inverter and then figure out what size you need based on what I previously said. Then go out to the great prophet in the sky (Google) and search for an inverter that will fill the bill. I don't use them so I don't have any personal recommendations. |
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| Author: | mix4fix [ May 18th, 2020, 7:40 pm ] |
| Post subject: | Re: 12VDC wattage requirement for 120VAC light |
tomp wrote: If you only draw 30 watts, this is a cost effective inverter that should have enough spare capacity to work with the fluorescent ballasts and it is quasi sine wave. https://www.harborfreight.com/80-watt-c ... 66944.html I stopped by there and I was looking at the 200/400 and 400/800 versions. I can't figure out the fusing needed for them. https://www.harborfreight.com/200-watt- ... 66967.html https://www.harborfreight.com/400-watt- ... 66814.html |
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