[RE-wrenches] Magnum inverters (not really a power factor issue)

Darryl Thayer daryl_solar at yahoo.com
Sat Aug 1 20:32:15 PDT 2009


BoB are you saying that wires that are so fat and really not very long less than 10 feet can have significant inductance?  I thought that inductance was from small wires wrapped into coils?  

Anyhow I thought the problem was battery internal resistance, and the building of the sine wave from pulses caused the problem..  I have seen battery breakers (thermal type) trip at lower current when feeding a pulse load.  To supply a 1000 watts it takes and average current of 80 amps at 12 volts, If that is supplied by a repeating half sine wave, it requires a peak current of 112 amps.  If the sine wave building pulses have a 50% duty cycle, the current could be as high as 224 amps peak.  

In Larry's case the simple inverter that takes only big pulses, the peak current for the  1000 watt load is only 80 amps.  (much easier on the battery.)
Darryl      

--- On Sat, 8/1/09, boB Gudgel <boB at midnitesolar.com> wrote:

> From: boB Gudgel <boB at midnitesolar.com>
> Subject: Re: [RE-wrenches] Magnum inverters (not really a power factor issue)
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Saturday, August 1, 2009, 9:08 PM
> Darryl Thayer wrote:
> > Don't know if this will help, but an experiance of
> mine on starting a large motor, using a battery and
> inverter.  The motor would not start, or if it did if
> would quit in 10, or 20 min.  The battery had capacity
> to run the motor for 5 or 6 hrs to 50% DoD yet the inverter
> would kick out.  I had reason to beleive the output
> wave form was bad also.  I solved the problem by
> greatly increasing the battery size and the cables.  I
> did not change the inverter at all.  
> >
> > What I think was happening is the high current draw of
> the inverter to serve the load reduced the battery voltage,
> but not just the average battery voltage but the 60 cycle
> peak voltage drop/ of the battery.  The load of the
> inverter on the battery is like pulses, my amp clamp shows
> an AC current on the battery leads.  If I had a scope,
> I would guess the inverter is seeing a fluxuating voltage on
> the battery.  My grandson has a 1 Farad Capacitor in
> his sterio system, perhaps this would fix the problem. 
> BoB what do you think?
> > Darryl
> >   
> Try it.  Put it right across the inverter DC terminals
> if you do try 
> it.   Sometimes, higher capacitance can
> actually make things worse, 
> like, raising the peak
> DC voltage seen at the inverter terminals due to L-C
> resonance.
> 
> boB
> 
> 
> 
> 
> > --- On Sat, 8/1/09, boB Gudgel <boB at midnitesolar.com>
> wrote:
> >
> >   
> >> From: boB Gudgel <boB at midnitesolar.com>
> >> Subject: Re: [RE-wrenches] Magnum inverters (not
> really a power factor issue)
> >> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> >> Date: Saturday, August 1, 2009, 6:22 PM
> >> Larry Crutcher, Starlight Solar
> >> wrote:
> >>     
> >>> Hey Matt, 
> >>> I sure wish their techie's would get to the
> bottom of
> >>>       
> >> it. I am getting gun-shy about selling Magnum and
> they are
> >> about the best available for small 12 volt
> systems. I have
> >> spend hours trying to solve the problem. My
> customer is
> >> still not a happy camper.
> >>     
> >>> Larry Crutcher
> >>> Starlight Solar
> >>> (928) 941-1660
> >>> Renewable Energy Products, Service and
> Installation
> >>>       
> >> Can you get someone to look at the voltage and/or
> current
> >> going into that pump ??   Scope
> >> ?   Meter ?  Even a
> >> power factor meter would have both voltage and
> current
> >> measurements.  Some even have a mediocre
> scope built
> >> in.
> >> A scope AND a meter is best of course.
> >>
> >> Need  stats.  AC an DC side.  AC
> voltage at
> >> the pump and at the inverter.
> >>
> >> Must have more information.    Yes, it
> ~could~ be
> >> a Magnum inverter issue, but need more information
> other
> >> than "it doesn't work"
> >>
> >> Does the voltage dip when the pump tries to start
> ? 
> >> What is the maximum Ac and DC current ?  Most
> basic
> >> info for troubleshooting.
> >>
> >> The inverter manufacturer can probably help
> somewhat if
> >> they have this info.
> >>
> >> Just a suggestion here.
> >>
> >> boB
> >>
> >>
> >>
> >>
> >>     
> >>>
> >>> On Aug 1, 2009, at 4:28 PM, Matt Tritt wrote:
> >>>
> >>>       
> >>>> I took boB's advice and talked to Magnum
> about the
> >>>>         
> >> problem. Their take on it? "Hmmm, beats me!" I
> might be
> >> paraphrasing, but that's the drift. All in all,
> I'd say that
> >> the suggestions from the group are at least as
> good as the
> >> one's from the manufacturer.
> >>     
> >>>> Matt T
> >>>>
> >>>> Larry Crutcher, Starlight Solar wrote:
> >>>>         
> >>>>> Don't forget, this is a Magnum
> inverter and
> >>>>>       
>    
> >> Magnum has issues. I have  two customers with
> Magnum
> >> problems. One is a washer that will work 
> perfectly on
> >> a cheap import inverter; the other has a Vizio TV
> that 
> >> works fine on shore power and generator.
> Soooo...maybe there
> >> are pumps  and other items that are
> anti-Magnum.
> >>     
> >>>>> Larry Crutcher
> >>>>> Starlight Solar
> >>>>> (928) 941-1660
> >>>>> Renewable Energy Products, Service
> and
> >>>>>       
>    
> >> Installation
> >>     
> >>
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