Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Maximum current draw on 12v supply?
Hi
Does anyone know what maximum current draw the 12v supply in the back of a Discovery can sustain?
I want to run a (preferably 1Kw) pure sinewave inverter from this supply and was just wondering what the maximum load was that I could run. Basically if it's not high enough i'll have to buy a small generator, incidentally, I plan to have the engine running whilst i'm using the inverter.
The vehicle also has the white power socket available as part of the towing electrics. Is this a more robust supply than the internal 12v?
The cables attached to the back of 12v cigar plug supply are no way heavy enough to pull the sort of current you are suggesting. The supply to the tow-bar electrics will possibly make more sense but I'm still dubious about suggesting this. Just what do you need 1kw for, and for what sort of duration? Generator would make a lot more sense IMO. At least you will be able to start the car after using it. The older I get, the more I realise that people confuse wrinkles for wisdom
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4th May 2009 3:59 pm
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Thanks for the reply JMC.
I pretty much figured the internal supply wouldn't be any good.
I need to run a specialised outdoor projection system from an adapted mount on the car roof. There will probably be no more than 500watt (if that) maximum draw on a continuous basis, there may be a peak current draw when the unit is switched on.
I'm still waiting on final specification from the manufacturer of the system so I can't be any more specific at this moment in time.
The reason for the 1Kw inverter is that is what the make I was thinking of getting comes in, well, that and 1.5Kw
Cheers
Jem
4th May 2009 4:16 pm
SJR
Member Since: 09 Aug 2006
Location: East Manchester
Posts: 4030
I think JMC has it spot on TBH
For that sort of drain get a generator
If you put up a new generator thread, someone is bound to know what to buy, from where, and for how much that will suit your needs 8)I believe that every human has a finite number of heart-beats. I don't intend to waste any of mine running around doing exercises.
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4th May 2009 4:25 pm
DiscoDunc
Member Since: 08 May 2006
Location: Bristol
Posts: 16390
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4th May 2009 4:31 pm
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
WOW
Generators have certainly come a long way since I last looked at them !
Pure sinewave from a generator... If it's as good as the blurb makes out this would do the job nicely. However... It would still be nice to run straight from the power outlet on the Disco
Cheers
Jem
4th May 2009 5:09 pm
drivesafe
Member Since: 23 Feb 2006
Location: Gold Coast, Australia
Posts: 867
Not sure how long you want to operate the inverter for but even at 500w, a hour would be about it and not only would your cranking battery be close to flat but a continuous current load of that size would also stuff your cranking battery.
You either need a generator or a bank of at least 3 x 100 A/H batteries wired in parallel and then you could supply your 500w for a few hours.
Even with a three battery set up, I still wouldn’t consider trying to pull a 1,000w from them.2008 TDV8 RR Lux + 2009 D4 2.7
6th May 2009 12:53 pm
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Thanks for the info guys, it's really helped
Having taken your replies into consideration I think a good generator is the way to go. I contacted Honda who have sent me load of tech spec sheets. It does indeed look as though the output from the little Honda generator that DiscoDunc recommended is pure sinewave. Taking that into account it's also a pretty good price when compared to a good quality (not Eb*y) pure sinewave inverter.
Also, a generator will probably prove a pretty useful thing to have about the place .
Thanks
Jem
6th May 2009 4:16 pm
dick dastardly
Member Since: 29 May 2007
Location: wiggleigh bottom
Posts: 1112
Back to school !
Power (watts) = Voltage(Volts) x Current (amperes)
So to get 1000 Watts you will need to draw 83 1/3 Amperes at 12 Volts. The 12V sockets will be fused at 20-30 Amps I guess (please advise).
If you draw 83 amps from the battery, it'll be theoretically dead in just over 1 hour, practically dead probably in 15 minutes.
Get a generatorThere's one wheel on my wagon, but i'm still rollin' along, it's the cherokee, they're after me, but I'm singing a happy song
6th May 2009 11:06 pm
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Decision made... A generator it is going to be. Going to get a Honda EU20i
One final question though... The generator will of course be used outside, what happens if it rains?, those electrical sockets look pretty exposed to me. Is there some sort of cover that you can put over it while it's running to protect it from the elements?, or am I supposed to switch it off when it rains
Well if you're planning on running a projector outside in the rain, can I come and watch?I know it's not considered "kind" to say no these days, but no. Just no, ok? And if it's not ok, still no.
7th May 2009 1:13 pm
Rescue01
Member Since: 14 Jan 2008
Location: Aberdeen
Posts: 2449
Hi Jem i noticed that costco are doing these gennies for £862 all in so may be worth a look.
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7th May 2009 1:24 pm
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Ahhh... but this is no normal projector, and it's weatherproof
Costco's price at £862 is very good. The best quote i've had is from an official Honda dealer in Normanton, West Yorkshire, called Seddons Ltd. They can do it for £897 inc. V.A.T.
Cheers
Jem
7th May 2009 2:44 pm
robsmith
Member Since: 02 Sep 2007
Location: Staffordshire
Posts: 2393
Jem wrote:
One final question though... The generator will of course be used outside, what happens if it rains?, those electrical sockets look pretty exposed to me. Is there some sort of cover that you can put over it while it's running to protect it from the elements?, or am I supposed to switch it off when it rains
Jem
Umbrella?
You are quite right, the outputs aren't rain resistant so would need some protection from the weather. I've used quite a number of small gennies outside and have found that it best to go up a size from what the calculations suggest, that way you don't suffer a frequency or voltage dip when you turn on the load, which can result in the failure of some electronics
Other things not to forget are an earth stake, and a good ELCB for protection - I've had a few tingles even with an earth stake in place. Depending on what the environment is like, and how noisy the gennie is an "L" shaped pile of straw bales can help a lot in cutting down noise getting to the wrong place. A tip here, try not to put the gennie with a hard surface reflecting the noise toward the crowd, much better a hedge.Rob Smith
Silver rools OK
8th May 2009 11:20 am
Jem
Member Since: 02 May 2009
Location: Yorkshire
Posts: 59
Thanks Rob, great and very welcome advice
I've just picked up the Honda EU20i generator from our local distributor this morning, hopefully i'll get time to fire her up over the weekend!
Great idea about the straw bales, ELCB's and the earth spike, i'll get that sorted out as well.
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