Sanyo panel & CControllers [RE-wrenches]

[Larry Crutcher, Starlight Solar]

Why don't the manufacturers of MPPT controllers just put a brick wall voltage clamp on the input? (Of course the answer is cost) A touch of hysteresis here and some time delay there and Voilà!  It would be great to have 2 Sanyo's wired in series. For the occasional few times a year that over voltage could occur, high voltage is prevented from reaching the input to do any damage.

My 19 Won or about 2 cents worth.
Larry Crutcher
General Manager
Starlight Solar

Retail Store & Shipping: 2998 Shari Ave. Yuma, AZ 85365
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  ----- Original Message ----- 
  From: Christopher Freitas --- OutBack Power 
  To: RE-wrenches at topica.com 
  Sent: Monday, February 04, 2008 3:54 PM
  Subject: RE: Sanyo panel & CControllers [RE-wrenches]



  Tump - I agree that reliability is the most important part of any 
  product - but its something that we can (and do already) know how to 
  achieve for a product like this...

  What I was talking about the engineering challenge of developing a high 
  voltage input MPPT product - that the converter's efficiency has to be 
  high enough to justify its cost - if the MPPT is only 95% efficient than 
  it might not "capture" much additional power for most of the year from 
  the PV array. Also, If the system has a 3000 watt PV array and it cost 
  $5/watt to install - then each single percent of the MPPT's conversion 
  efficiency is worth $150... 

  The greater the difference between the PV array and the battery voltage 
  - the lower the efficiency of the DC-DC converter.  Sure - there are 
  tricks that can be done to reduce these losses - but they tend to make 
  the product much more expensive - again reducing the overall "value" in 
  the end.  

  The bottom line is everything has trade-offs.  Higher voltage MPPTs will 
  cost more, will be less efficient, and will be lower power than the 
  current MX60 & FM80.  They can reduce the system installation cost by 
  requiring fewer strings, smaller wire, smaller conduits - but only time 
  will tell what wins out in the end...

  There also is the option of doing AC coupled systems with grid-tie 
  inverters - which allows for up to 600 VDC PV arrays right now - but a 
  3000 watt grid-tie inverter is over $2000 - which would pay for a fair 
  amount of additional wire and labor... and most of the grid-tie 
  inverters are only 95% or so efficient... 


  Christopher

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


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