Battery Drawdown

Submitted: Thursday, Oct 30, 2014 at 16:52
ThreadID: 109990 Views:1791 Replies:4 FollowUps:15
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A Question for the Electronics Guru's.
If I run a standard 240v Spotlight with a 16 watt LED Globe through an inverter, does it use the same amount of power amps as a 16 watt 12volt light?
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Reply By: John and Regina M - Thursday, Oct 30, 2014 at 17:02

Thursday, Oct 30, 2014 at 17:02
No
It uses more
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Follow Up By: Mazdave - Thursday, Oct 30, 2014 at 17:04

Thursday, Oct 30, 2014 at 17:04
Any idea how much more?
I am sure there is an equation to work it out that someone out there will know
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Follow Up By: Notso - Thursday, Oct 30, 2014 at 18:14

Thursday, Oct 30, 2014 at 18:14
It depends on how efficient the inverter is.

If it was 100% efficient then it would be about the same, if it was 80% efficient it would theoretically use 20 watts of power to make your useable 16 watts. There are probably other variables that would affect it too, but you'd need an proper electronics guru for that.
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Follow Up By: Gronk - Thursday, Oct 30, 2014 at 18:35

Thursday, Oct 30, 2014 at 18:35
It will use about the same ( except for losses mentioned already ), but it's far easier to use a 12V globe seeing as it looks like you want to use 12V as the power source.

Everyone has a fixation with inverters, but if you can avoid them, the better, as 240 V is not something to have around a camper or vehicle if not absolutely necessary ..
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Follow Up By: Bludge - Thursday, Oct 30, 2014 at 19:22

Thursday, Oct 30, 2014 at 19:22
I cheated and used

Volts - Watts - Amps calculator

12 volts @ 16 watts = 1.33 amps

240volts @ 16 watts = 0.066 amps plus the inverter losses.

so with 20% for the loss through the inverter
240 v @ 20 watts = 0.083 amps

So all in all its down to carrying inverters and 240v items against pure 12v items
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Follow Up By: Life Member - Terry 80FTE - Thursday, Oct 30, 2014 at 21:35

Thursday, Oct 30, 2014 at 21:35
I think the inverter would draw more than 0.083 amps just to turn on.
Did you factor in the fuel usage to cart the extra weight of the inverter around or do you just carry it anyway, they are quieter than a genny that said, unless you need to run the vehicles engine to charge up the battery :)
I use2x 10 amp LED floods straight off 12v as it saves mucking about,
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Follow Up By: Allan B (Member, SunCoast) - Thursday, Oct 30, 2014 at 21:48

Thursday, Oct 30, 2014 at 21:48
Terry, I think you mean 2x 10 WATT floods, not 10 amp.
At 20 amps, you battery would be flat in a couple of hours!
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Follow Up By: Life Member - Terry 80FTE - Thursday, Oct 30, 2014 at 21:59

Thursday, Oct 30, 2014 at 21:59
Haha Yeah! you're spot on there Alan.
I think I need a better proof reader, they would put out a lot of light though.
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Follow Up By: The Bantam - Thursday, Oct 30, 2014 at 22:01

Thursday, Oct 30, 2014 at 22:01
Don't forget you have two conversion losses.

you have losses in conversion from 12 to 240v and you have losses from 240 back to 12 volts ( or whatever voltage the led works at).

The whole point of LED is the rediculous effiency that can run at.

You may find converting from 12 to 240 and backagain will produce more losses than the LED consumes in the first place....AND a 16 watt led is a pretty bright thing to have arround the camp site.

Oh and consider too...even if the LED light you have runs direct off 240v and not thru a transformer or electronic converter...it will most likely be less efficient than a light running 12 volt native.

Led lamps and lights that run 12 volt native are soo cheap these days, why would you fiddle with double conversions and unnecessary 240V power.

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Follow Up By: Allan B (Member, SunCoast) - Thursday, Oct 30, 2014 at 22:03

Thursday, Oct 30, 2014 at 22:03
LOL Terry. 120 watt LED floodlights don't bear thinking about!
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Follow Up By: The Bantam - Thursday, Oct 30, 2014 at 22:04

Thursday, Oct 30, 2014 at 22:04
OH as for exactly how much more power will be consumed...thet will depend a great deal on exactly what equipment is being used.

Some inverters will have more than 16 watts idling consumption.

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Follow Up By: Zippo - Friday, Oct 31, 2014 at 12:23

Friday, Oct 31, 2014 at 12:23
Bludge: "so with 20% for the loss through the inverter 240 v @ 20 watts = 0.083 amps"

Yes, but that's the current @240V. It's still 20W (in your example) ex the 12V source.

To the O/P, as others have suggested always try and get a 12V device rather than an inverter/240V combo, for both efficiency/battery draw and SAFETY reasons.
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Follow Up By: Bludge - Friday, Oct 31, 2014 at 12:51

Friday, Oct 31, 2014 at 12:51
Zippo

With all due respect.

At no stage have I suggested using an inverter, I purely used a calculator with a link for Mazdave, to put in the figures presented by the OP and Notso after Mazdave posted:
"Any idea how much more?
I am sure there is an equation to work it out that someone out there will know"

I ended with
"So all in all its down to carrying inverters and 240v items against pure 12v items"

I did not express an opinion either way so I do not understand your post to me.
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Follow Up By: Zippo - Friday, Oct 31, 2014 at 13:15

Friday, Oct 31, 2014 at 13:15
Bludge, all I see is a calculation leading to an amps figure (@240V). For the O/P this info can be either useless or misleading him into thinkingthat it will be that drain on his 12v system. Maybe a tad more than the figure would have avoided that.
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Follow Up By: Bludge - Friday, Oct 31, 2014 at 13:45

Friday, Oct 31, 2014 at 13:45
Thanks again Zippo,

I cannot help it if you see only what you want to see.

Did you see "12 volts @ 16 watts = 1.33 amps" ?

His question was about running 240v through an inverter and some equation to find out what it would be.
Hence
240volts @ 16 watts = 0.066 amps plus the inverter losses.
so with 20% for the loss through the inverter 240 v @ 20 watts = 0.083 amps

The calculations are just that calculations. This is what the OP asked for.

There are sufficient people on here with opinions who can fill in gaps, Bantam did so with "conversion loss and that some inverters will have more than 16 watts idling consumption".

Allan B has said basically the same thing, although he has said he wouldn't do it.

Again I offered no opinion either way. I don't see anywhere in the forum rules where I must offer an opinion, or one that suits you.

Deal with it.



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Reply By: Allan B (Member, SunCoast) - Thursday, Oct 30, 2014 at 21:44

Thursday, Oct 30, 2014 at 21:44
Anything run through an inverter will use about 20% more from your battery than a 12v model of the same rating run directly from the battery.
So inverters are useful if your appliance only comes in a 240v model.
If you already have the inverter and the 240v spotlight and don't want to replace it with a 12v spotlight, then fair enough, but not good.
The other issue is that you will be running a 240v appliance in conditions that may be hazardous. Not the best idea for safety.
To sum up.......... I would not do it!
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Reply By: olcoolone - Friday, Oct 31, 2014 at 08:16

Friday, Oct 31, 2014 at 08:16
Mazdave....... can I ask why you want to do it that way and not just buy a 12v light.

The more things you add in a circuit the more complicated it becomes and the more chance of a problem developing.

Is it to save a bit of coin?
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Follow Up By: Mazdave - Friday, Oct 31, 2014 at 11:50

Friday, Oct 31, 2014 at 11:50
No not really, I have just purchased a 120w folding solar panel to charge my batteries and am doing away with the Generator. As a result of allways having a camp set up with the generator we used the spot lights for camp light. I all ready had the inverter and thought well I can just use the existing spots through the inverter. But upon trialling it it appeared to use more power than a general 16w 12v light. The answers given basically confirms my thinking and I have ordered a 12v LED spotlight which will plug into an existing Narva outlet.
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Reply By: Mazdave - Friday, Oct 31, 2014 at 14:27

Friday, Oct 31, 2014 at 14:27
Thank you to all contributors for their advise and "lively Debate"
As is all ways the case, you post a question you will get a variety of answers, but ultimately you will get the right answer
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