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06-03-2019, 11:55 PM
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#1
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Junior Member
Join Date: Jun 2019
Posts: 7
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100W 120V LED vs 100W 12V LED Electrical Question
I’m exploring electrical setups for my future RV. Let’s say I have a 3000W inverter and a 100 amp-hour battery. Of two led lights, a 100W 120V and a 100W 12V, which would drain the battery faster?
Thanks,
Mike
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06-04-2019, 12:44 AM
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#2
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Senior Member
Join Date: Feb 2012
Location: Lake County, IL
Posts: 1,584
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The 100W 120V LED would drain the batteries faster, because you would have to power it from an inverter, which would not be 100% efficient so there would be significant losses.
That being said, are you sure that you have your numbers correct? I have never come across a 100W LED for any voltage. A 10W LED is a big one.
Joel
__________________
Retired electronics engineer. Avid paddler & birder.
2011 Silverado 2500HD, diesel, 4x4,crew cab, 8' bed
Palomino Puma 253FBS (27' 5er) & '94 19' Class B
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06-04-2019, 02:32 AM
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#3
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Senior Member
Join Date: Jul 2014
Posts: 35,446
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The 100 Watt, 120 volt LED will draw .8 amps.
Creating 120 volts from 12 volts, thru an inverter is a 10 to 1 conversion, so it will draw 8 amps at 12 volts. Add the 10% to 20% losses thru the inverting prosses ( no inverter is 100% effecent ), and your looking at another about 1.5 amps. Next you need to add the 1/2 to 4 amps the inverter draws just being on. Depends on the inverter.
8 amps for the LED + 1.5 for inefecency + 2 amps inverter draw = 11.5 amps.
11.5 amps for 1 hour is 11.5 AH, so your battery will light the light for 8.6 hours before its dead.
The 100 Watt, 12 volt LED will draw 8 amps. Leave it on for 1 hour and it will draw 8 AH.
You battery will light the LED for 12 hours before your battery will be dead.
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06-04-2019, 03:55 AM
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#4
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Member
Join Date: Mar 2018
Location: Highland, Ca
Posts: 36
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I have to say....it is so comforting that we have so many people here that can break down complex scenarios for those of us that are “complexed challenged”.
Yes am truly grateful for those that do, and hope I will be able to understand the info they share.
Mike
__________________
2001 Rexhalle XL 3550 BSL
Demco Kar Kaddy SS
2015 Chevy Spark
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06-04-2019, 05:17 AM
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#5
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Senior Member
Ford Super Duty Owner
Join Date: Dec 2010
Posts: 1,799
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TwinBoat is right on the money, but I think the whole question is probably academic. Most coaches have all the accomodation lighting on the 12 volt side. It would be a serious customization to feed them with 120 volts anyway.
Either way, LEDs are low voltage, DC devices so keeping them on the low voltage DC side is the best solution anyway.
__________________
Scott Brownstein
Palm Island, Florida
2015 Georgetown 335DS
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06-04-2019, 08:35 AM
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#6
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Senior Member
Join Date: May 2018
Location: Benson AZ
Posts: 512
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LEDs are low voltage DC devices that run about 3.6v each. Don't try that directly, it would be too easy to fry it.
__________________
Retired Engineering Technician, 2023 Artic Fox 25Y TT
SOLD 2017 Winne Minnie 2201DS TT
SOLD 2010 Chalet XL1930 A-Frame TT
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06-04-2019, 11:21 AM
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#7
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Junior Member
Join Date: Jun 2019
Posts: 7
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Quote:
Originally Posted by twinboat
The 100 Watt, 120 volt LED will draw .8 amps
8 amps for the LED + 1.5 for inefecency + 2 amps inverter draw = 11.5 amps.
11.5 amps for 1 hour is 11.5 AH, so your battery will light the light for 8.6 hours before its dead.
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Don’t you mean 0.833 amps + 1.5 + 2 = 4.3?
Where can I find the numbers for the inverter? Would I have to contact the manufacturer?
Also, would a 4000 watt inverter use more power than a 2000 watt inverter?
Thanks,
Mike
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06-04-2019, 11:24 AM
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#8
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Junior Member
Join Date: Jun 2019
Posts: 7
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Joel, I was looking at outdoor floodlights, not individual leds.
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06-04-2019, 11:38 AM
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#9
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Senior Member
Join Date: Jul 2014
Posts: 35,446
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Quote:
Originally Posted by Sailmike
Don’t you mean 0.833 amps + 1.5 + 2 = 4.3?
Where can I find the numbers for the inverter? Would I have to contact the manufacturer?
Also, would a 4000 watt inverter use more power than a 2000 watt inverter?
Thanks,
Mike
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The idle current should be listed in the specs. May be listed as amps or watts.
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06-04-2019, 11:45 AM
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#10
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Senior Member
Ford Super Duty Owner
Join Date: Dec 2010
Posts: 1,799
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Quote:
Originally Posted by Sailmike
Don’t you mean 0.833 amps + 1.5 + 2 = 4.3?
Where can I find the numbers for the inverter? Would I have to contact the manufacturer?
Also, would a 4000 watt inverter use more power than a 2000 watt inverter?
Thanks,
Mike
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Inverter efficiency is a moving target. However, the bigger the inverter the higher the idle current. If you only need 300 watts, a smaller inverter will waste less than a bigger one. Low load on a big inverter probably has pretty high losses in efficiency as well.
Two small ones is better than one great big one.
__________________
Scott Brownstein
Palm Island, Florida
2015 Georgetown 335DS
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06-04-2019, 12:04 PM
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#11
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Junior Member
Join Date: Jun 2019
Posts: 7
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Does the idle current include both inefficiency and inverter draw? Or do I just have to assume 1.5 amps lost?
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06-04-2019, 12:10 PM
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#12
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Registered User
Join Date: Oct 2017
Posts: 4,985
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Quote:
Originally Posted by Sbrownstein
Most coaches have all the accomodation lighting on the 12 volt side. It would be a serious customization to feed them with 120 volts anyway.
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We have 2 plug in 120V table lamps in our fifth wheel that we added.
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06-04-2019, 12:28 PM
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#13
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Senior Member
Ford Super Duty Owner
Join Date: Dec 2010
Posts: 1,799
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Idle current is with no load. Efficiency is another thing and I think it gets better as the load increases on a given design.
__________________
Scott Brownstein
Palm Island, Florida
2015 Georgetown 335DS
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06-04-2019, 12:54 PM
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#14
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Junior Member
Join Date: Jun 2019
Posts: 7
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Looking at a few inverter specifications, I didn’t see any listing for idle current for any of them. What do I look for?
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