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I've inherited 4 custom built solar panels. These are not consumer grade panels but industrial sized. They produce 680 volts DC at 3.8 amps. The voltage selection was probably selected to minimize the amperage and minimize current loss from transmission. That said, I would like to put these panels to work. I want them to produce as much 240, single phase power as possible. The intended use is to be off grid. The largest off the shelf charge controller I can find is the Xantrex 80 (amp)-600 (volt) XW. The voltage from the panels exceed this and I'm not finding a buck converter that will bring the voltage down to 550 or less. I am not an electrical engineer so please be explicit. I did install a grid tied system so I'm not totally clueless. :-)

What are my options?

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    \$\begingroup\$ Do you know if they are "680V open-circuit", or "680V maximum power"? \$\endgroup\$
    – bitsmack
    Sep 28, 2015 at 21:38
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    \$\begingroup\$ 680V open-circuit \$\endgroup\$ Sep 28, 2015 at 21:50
  • \$\begingroup\$ Since ready-made commercial MPPT controllers top out at 600V as you noticed (not just Schneider's-- the mass produced parts used in these have a "standard" rating of 650V), I guess these panels were used with a PWM controller before, no? PWM will lose you some 20%-25% charge. Whatever solution you find for using an MPPT ctrl, you need to compare with that as a baseline. \$\endgroup\$ Sep 28, 2015 at 23:18

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240V from a decent H bridge needs a 350V DC supply roughly and I would think about making 350V DC (from the 680 volts) with another H bridge driver circuit dedicated to converting 680 volts DC to 350 volts DC using a transformer, rectifer and smoothing capacitor.

I'm chickening out a bit here because, I feel, using a H bridge to convert straight to 240V AC may be too big of a step but, others may offer advice to the contrary and I will look forward to their suggestions.

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  • \$\begingroup\$ Andy, my feeling is that if I get the voltage under 550, I'll feed it to the XW-80-600 MPPT charge controller and let it do what it does best. The tech specs for the XW-80-600 says that it prefers 550 volts or less. \$\endgroup\$ Sep 28, 2015 at 21:53
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    \$\begingroup\$ Wouldn't it be easier to just reconnect the panels into multiple serial banks that produce lower voltage & then connect them to one or more charge controllers/inverters? \$\endgroup\$
    – DIYser
    Sep 30, 2016 at 12:25
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Why not make your own buck convertor but not with const v out but with v out a specific fraction of V in .Say if you make your fraction one half ,Then V out max will be 340 VDC which will suit the OTS equipment you want to use .Now the MPPT will track and the system will perform at a wide range of light levels .The losses in a sensibly designed converter will be a few % which is acceptable.

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