Date: Thu, 11 Dec 2008 14:42:51 -0800
Reply-To: David Kao <dtkao0205@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Kao <dtkao0205@YAHOO.COM>
Subject: Re: Pure Sine Wave Inverter
In-Reply-To: <BAY132-DS59B3C69600FD5AEC64D2DA0F80@phx.gbl>
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I can imagine at least one reason why one will want an inverter of
an incredible kilo watts, despite the fact the battery is not
capable of energizing such an inverter.
Every inverter uses a transformer to convert the DC voltage of
12 volt to AC of 120 volt. This transformer is operating at above
100 KHz to maximize the conversion efficiency and also to eliminate
low frequency hum. The core of this transformer can be saturated
before the inverter reaches its claimed max wattage. When this
happens the output voltage will drop and the waveform (sinewave)
will lose its shape. The inverter will not function properly. Cheap
inverters tend to have this problem.
A 2 kw inverter probably will not have the problem when driving a
500 watt load, but a 1 kw inverter probably will. So I don't think it
is too crazy to use a 2 kw inverter. However, a 2 kw inverter will
draw a higher current than a smaller one when there is no load
connected. You definitely will want to turn it off when not in use.
I use a small 100 watt inverter for my laptop. It works great. The
laptop only sucks less than 30 watt. The inverter works really well
at this load.
David
--- On Thu, 12/11/08, Dennis Haynes <d23haynes57@HOTMAIL.COM> wrote:
> From: Dennis Haynes <d23haynes57@HOTMAIL.COM>
> Subject: Re: Pure Sine Wave Inverter
> To: vanagon@GERRY.VANAGON.COM
> Date: Thursday, December 11, 2008, 8:46 AM
> Obviously I meant to type 2kw. I guess the 000 was habit.
>
> You really size the batteries for the full load rating of
> the inverter. The
> surge rating is really for motor starting or other short
> term bursts. Some
> inverters can only support that surge for a second, minute
> tops.
>
> Ideally you want to size your batteries for supporting a
> load over a 6 hour
> rate. 4 hours can still be acceptable.
> 2 group 31 batteries will support a 1,000 watt inverter.
> 2 golf cart batteries (225 A/H) in series will work much
> better and last
> longer. They are available in AGM also.
>
> You also need to consider charging the batteries. From
> experience the stock
> Subaru alternators do not like large battery banks. As soon
> as they heat up
> they go into current limiting and watch the voltage drop.
> There are high
> performance alternators out there for the Subie. The
> problem with them is
> low output at idle.
>
> The battery you're looking at appears to be an absorbed
> glass mat, (AGM).
> These require some special charging cycles so an addition
> to alternator
> charging, you need a good smart charger to maintain these
> things. Plan on
> short life. This is an over stated technology.
>
> Unless you really like to be bothered with battery use,
> forget the selector
> switch and consider automation. Chassis battery, house
> batteries, and a
> charge control relay.
>
> Are you planning to hard wire the 110v into outlets
> installed in the van? If
> so the inverter needs to be designed and rated for that.
> Keep the stock group 41 battery for the chassis. Run a
> separate charge line
> from the alternator.
>
> Consider getting an inverter/charger with pass through/auto
> changeover of
> the 110v side. Now you can really get rid of money.
>
> For charging battery operated devices, almost all
> rechargeable devices have
> 12 volt car cords available. This is the best way to go.
>
> Dennis
>
>
>
>
> -----Original Message-----
> From: Vanagon Mailing List
> [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> M'obeechi
> Sent: Wednesday, December 10, 2008 11:30 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Pure Sine Wave Inverter
>
> Thats a good question. Let me ask my accountant.
>
> http://www.sears.com/shc/s/p_10153_12605_02850131000P?vName=Automotive&cName
> =Batteries+%26+Chargers&sName=Marine+Batteries
>
> I want three of these (dig those handles:)! Though I can
> combine all three,
> most usually only two will act as than house bank, or house
> battery.
>
> Honestly, not sure how you determine how much is needed to
> support a surge
> to 2000kw, and I've got this book next to me,
> Electricity and Electronics by
> G. Randy Slone. I've glad you asked though, because I
> was getting carried
> away lusting at even bigger units. Now that I'm
> grounded can you help me
> understand how to calculate this?
>
> You know those Exeltech's are said to be in every US
> Embassy in the world.
> So if I get one those, I might have an "in" with
> an overseas assignment.
>
> Pure sine wave, because my XM 1000 Xantrex states that it
> doesn't mix well
> with rechargeable devices, and I've already had a
> problem with batteries
> dying right after using with the Xantrex. Rather than
> debating and
> empirically determining the cause, I'd rather eliminate
> the possibility,
> which could actually end up saving me money. The inverter
> (pure sine wave)
> will be in the 500 dollar range.
>
>
>
> From: "Dennis Haynes"
> <d23haynes57@hotmail.com>
> To: "'M'obeechi'"
> <obeechi@RUNBOX.COM>,
> <vanagon@GERRY.VANAGON.COM>
> Subject: RE: Pure Sine Wave Inverter
>
> > Why pure sine wave and do you know how many batteries
> are needed to
> support
> > 2kw?
> >
> > Dennis
> >
> >
> > -----Original Message-----
> > From: Vanagon Mailing List
> [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> > M'obeechi
> > Sent: Wednesday, December 10, 2008 7:49 AM
> > To: vanagon@GERRY.VANAGON.COM
> > Subject: Pure Sine Wave Inverter
> >
> > I looked at the archives, but its not working right
> now.
> >
> > There aren't any reviews online that I can find
> regarding pure sine wave
> > inverters.
> >
> > For now it looks like Exeltech, Samlex, and Cotek
> might be good. But there
> > are others too. I'm wanting 1000 watt range with
> 2000 watt surges.
> >
> > Anyone have any leads? Thanks.
> >
> >
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> >
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