240v inverter from 12v side of generator

Submitted: Sunday, Mar 14, 2010 at 09:48
ThreadID: 76838 Views:2949 Replies:5 FollowUps:6
This Thread has been Archived
hello. can anyone tell me if i can use a 240v inverter ( say 1000w , but only using 500w draw ) straight from the 12v output on a portable generator.
Back Expand Un-Read 0 Moderator

Reply By: Member - Barry (NT) - Sunday, Mar 14, 2010 at 10:01

Sunday, Mar 14, 2010 at 10:01
Not portable generators to the best of my knowledge

my 1000 w inverter can draw up to 70-80 amps DC from the battery so this is clearly out of range of the portable type generators

even 500 w AC draw is likely to draw 5 A Dc from batteries just to run the ineffcient inverter

however the experts may prove me wrong, but unless something has changed recently the answer is no

AnswerID: 408748

Follow Up By: qubert - Sunday, Mar 14, 2010 at 10:05

Sunday, Mar 14, 2010 at 10:05
yeah thanks. just did calcs as well. way out of range of what it makes . was silly idea........
0
FollowupID: 678693

Follow Up By: Battery Value Pty Ltd - Sunday, Mar 14, 2010 at 10:41

Sunday, Mar 14, 2010 at 10:41
240VAC gennies with an additional '12VDC' output generally produce a raw rectified sine wave. You could call this a pulsed DC voltage.

Your 12VDC/240VAC inverter most likely has some smoothing capacitors on the input side.
This means you can start the inverter, with a very small load of say less than 0.1A on the 240VAC (<25W)
Any more load, and the inverter will probably undervolt.

One trick you could do is to wire a flooded type battery of any capacity in parallel to the inverter input which effectively smoothes out the high ripple from the gennie and your inverter will be happy to produce the Watts needed by the 240VAC appliance.

Just be aware that the '12VDC' output won't give you a lot of juice, maybe only 4 or 5 amps, before the voltage becomes too low to charge the battery and supply the inverter.
This means you have to limit the 240VAC loads to around 40 Watts time averaged (this allows for ~20% inverter inefficiency), or the battery will get drained.
Because of the battery acting as an energy buffer you can draw up to your inverter's maximum rating, but only in spurts (keeping the time averaged draw to below 40 Watts).

Hope this gives you some fresh ideas.

Best regards, Peter
0
FollowupID: 678699

Follow Up By: Battery Value Pty Ltd - Sunday, Mar 14, 2010 at 11:04

Sunday, Mar 14, 2010 at 11:04
Forgot to mention this:
The only situation when a setup similar to the one above would make sense, is when you have a small generator, and high inrush 240VAC power tools like big angle grinders or similar.

Then you'd want to have a 25A battery charger running off the gennie 240VAC, charging a 12V battery which is used to power your beefy inverter.

That way you can start your inrush hungry power tool without stalling/tripping the gennie.

Best regards, Peter
0
FollowupID: 678700

Reply By: dbish - Sunday, Mar 14, 2010 at 10:06

Sunday, Mar 14, 2010 at 10:06
Hi qubert, definetly not 300w inverters draw about 30Amps at full load. Daryl
AnswerID: 408749

Follow Up By: Member - Barry (NT) - Sunday, Mar 14, 2010 at 10:20

Sunday, Mar 14, 2010 at 10:20
not necessarily so

my 400 modified wave inverter draws 8A DC and then trips off due to overload, so not anywhere near 30 A

one size doesn't fit all,,, inverters are notorious for inefficiency
0
FollowupID: 678695

Follow Up By: dbish - Sunday, Mar 14, 2010 at 11:25

Sunday, Mar 14, 2010 at 11:25
Hi Barry, I also use a 300w MSW inverter a Power house from Altronics, It draws 30Amp when powering a 300W flood light. If yours is triping out at 8Amp its probably from low voltage as 8Amp is only about 90Watts. cheers Daryl
0
FollowupID: 678701

Reply By: Member - Fred B (NT) - Sunday, Mar 14, 2010 at 10:44

Sunday, Mar 14, 2010 at 10:44
the 12v outputs of gensets are rarely pure and nver designed for "load". They are (normally) to be used for battery charging only.... read your handbook...
regards
Fred B
VKS 737: Mobile/Selcall 1334

Lifetime Member
My Profile  My Blog  My Position  Send Message

AnswerID: 408750

Reply By: Member - Allan B (QLD) - Sunday, Mar 14, 2010 at 11:03

Sunday, Mar 14, 2010 at 11:03
Hi Qubert, I imagine that your generator is the usual 240vac plus 12vdc outputs, so why would you want to derive 240vac via an inverter when you already have it available directly from the gennie?

Cheers
Allan

Member
My Profile  My Blog  My Position  Send Message

AnswerID: 408753

Reply By: Member - Doug T (NT) - Sunday, Mar 14, 2010 at 12:39

Sunday, Mar 14, 2010 at 12:39
Like the post above, got me whacked why you would use an Inverter , why not just plug the appliance into the gennie.

.
still going strong with 836,179 K's

Lifetime Member
My Profile  My Blog  Send Message

AnswerID: 408768

Follow Up By: Member - Doug T (NT) - Sunday, Mar 14, 2010 at 12:43

Sunday, Mar 14, 2010 at 12:43
I think I know where this is heading, 1000w gennie, 500w Inverter = 1500w .
Haaa Haa.

.
still going strong with 836,179 K's

Lifetime Member
My Profile  My Blog  Send Message

0
FollowupID: 678712

Sponsored Links

Popular Products (14)