[RE-wrenches] Magnum MS 4448 AE issues

[Ray Walters]

I've seen those dips in output voltage from almost all off grid 
inverters under load.   They either dip the voltage or worse (like an 
old Trace SW5548) just shut off. Outback for instance just has a 
constant 50 amp output for 5 sec, and lets the voltage dip a bunch on 
surges.  The idea is to to run them like a generator, which also dips 
voltage on surges.

2nd,  I know he didn't measure much volt drop on the DC side, but I've 
had poor results with Rolls batteries under load.
3rd, I didn't know the Sky stream was recommended for off grid,  I 
thought it was grid tie only.  I could see the Sky stream shutting off 
every time a large load came on.  It probably would not work very well 
on generator power either.
One fix would be to have separate inverters, to isolate the Sky stream 
from the surge loads.
The only inverter I haven't tried is the Sunny Island, but I would 
imagine it would have a voltage dip on surge too.
Perhaps some capacitance might help too?

Ray Walters
Solarray, Inc.

  On 12/23/2012 8:45 AM, Howie Michaelson wrote:
> Hi All,
>
> I am trying to help my brother-in-law figure out if he can continue using
> his Magnum MS 4448 AE in his now off-grid home in Nova Scotia which we
> installed about 3 years ago as at the time a battery backup inverter.  I
> would preface the following with the information that he is a very
> knowledgeable/hands on physicist (chair of the Physics department at
> Dalhousie U. in Halifax, as well as an intrepid sailor having sailed all
> over the world in 2 different sailboats he built himself).  I mention this
> to explain that he is very capable and understands the inner workings of
> his equipment much better than most wrenches I know (and certainly me).
>
> About a year ago he installed a SkyStream 3.7 to add to the roughly 3 kW
> of solar on an FM80, and then a short time later disconnected himself from
> the grid.  He immediately started having problems with the Skystream
> regularly disconnecting from his system and shutting down, then
> reconnecting and cycling off again, were as there hadn't been a problem
> while grid-tied.  After much investigation and conversation with SW
> WindPower tech support and some software patches from them, things
> improved somewhat.  But the regular disconnections continued.
>
> Since then he has spent a great deal of time on the phone with Magnum's
> tech support but they have not been able to answer his more technical
> questions.  The best they've offered is to have him send the inverter in,
> but of course that is now not practical.
>
> The basic problem seems to be the voltage regulation during loading and
> unloading of the inverter (even with medium sized loads). He tried to get
> an internal wiring diagram and/or service manual from Magnum with no luck.
>   He has not been able to get through to any engineers that would be able
> to answer his more technical questions.  He is trying to figure out if
> there are any internal set points that he can adjust or components that
> can use tweaking. He has looked at the wave form with a scope and would
> like to see if there are changes that he can make to the electronics to
> allow for better regulation.
>
> Here is what he has written me:
>
> "Here is my report on the Magnum MS4448AE observing the AC output with a
> Fluke 189, measuring the max and min values in slow mode (not it's fast
> mode which would look at spikes for short times):
>
> I have checked several water heater elements running on 240 V (they are
> between 2000 and 2500 Watts - immersion heaters). When switching any one
> of them on, the voltage drops from around 240V to 197 V on average,
> sometimes going as low as 170 V. These are serious drops, the lights dim
> drastically and the radio may cut out for .5 s or so! Switching the
> thermal heaters off again raise the output voltage to 271 V sometimes
> reaching 282 V.
>
> The battery bank during those test were at 53 V at the DC input side of
> the inverter, measured at the inverter. The voltage drop for the DC was
> around 1 V DC. The battery bank is a 800 AH (Rolls S530) with 2/0 copper
> cables 5 - 6 ft inverter cables.
>
> We had great wind yesterday and I had to switch to the hock up the
> diversion load to 240 V so it would draw 2.5 kW.  Needless to say it
> stalled the windmill each time my outback kicked on the diversion load. I
> had to leave  the windmill off during the day. When I run the heating
> element on 120 V (and therefore 625 W) it works beautiful if the wind
> isn't too strong. Obviously the inverter handles 625 W quite well!"
>
> He is also thinking about replacing the inverter with a newer split phase
> inverter (an XW or a Radian).  If anyone has an opinion about which might
> work for him, I'd appreciate any feedback.  I am not a fan of Xantrex,
> although I know some on the list really like the XW. If anyone has any
> ideas of either a fix or someone we can get through to at Magnum, that
> would be a great help.
>
> Thanks,
> Howie