MX60 question [RE-wrenches]

Christopher Freitas --- OutBack Power cfreitas at
Tue Sep 21 12:36:23 PDT 2004


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marco mangelsdorf wrote:
> The BP3160Q is an oddball module with a 23.8 Vmp and 30 Voc.  So four in 
> series here in the tropics shouldn't come close to the 140V max for the 
> MX60, right

Sorry for the slow response on your question - glad to see others 
helping out.  I actually was visiting Darryl Thayer's 40kW+ OutBack 
gridtie system on Friday - very impressive installation that is working 
well - although he had to do too much custom installation hardware as 
the space allowed for the equipment was very small and challenging.  

If the VOC on the modules you are using is 30 VDC and the location 
doesn't get too cold (below freezing) than I would say your fine.  It is 
likely that the open circuit voltage will exceed our current ETL listing 
of 120VDC - we are planning on retesting soon to increase the approved 
limit to the factory max VOC rating of 140VDC.  

As far as the choice of going with a one, two, three or four in series - 
it depends on numerous factors such as the distance of the PV array to 
the controller and if any partial shading is present. From my 
observations so far - I think wiring panels up for high voltages when 
short distances are involved compared to putting them in parallel is a 
wash - yes the efficiency of the MX60 goes down slightly with the high 
PV array voltages charging into a low battery voltage (about 1 or 2 
percent less) but the losses in the wiring are less and the PV array 
will start charging slightly earlier and will work better under 
partially shaded conditions and when subjected to high ambient 

We have recently installed two identical PV arrays which will allow us 
run side-by-side tests of both a low voltage system and high voltage 
system charging into the same battery with the voltage being sold back 
into the grid.  The results of this will be published on our website and 
I will announce it once available.  

As far as moving to Hawaii - keep in mind that there is areas with snow 
there too!  

Christopher Freitas
OutBack Power Systems, Inc.
cfreitas @
Arlington WA USA
Tel 360 435 6030  

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