1st time post - ? about higher voltages 72.9v

KD0CAC · September 2018

I have been around alternative energy almost 40 yrs. , and was for older systems [ not as old as 40yrs ] but have been using the limit of 48v as a high .
And found a craigslist add with some 425w 72.9v panels .
I was under the impression that generally 48v was where the limit was - not counting panels with mini-inverters mounted on panels .
Have not noticed any gear for higher voltage , maybe because what I have used in the past , hole house RV systems running airconditioning and everything , with 3500watt surge , 2000watt continuous , 600-1000watt total solar .
A little bragging - but to also make the point of correct system design - makes for long battery life - the proof is with the above system mostly no grid , the Trojan L16's lasted over 12 1/2 yrs.
So how much use and how rare of gear to build with 72.9 volt panels .

Thanks John

littleharbor2 · September 2018

Grid tied systems are now running up to 1000 VDC in some areas. Completely different creature than Off Grid battery based systems. While there are higher voltage battery backup systems they are generally only commercial systems and are under a whole different set of regulations than residential off grid. There are high voltage MPPT charge controllers that allow you to run up to 600 Vdc but you still will be charging a lower voltage battery bank which will be powering a lower voltage inverter.

There are many high voltage solar panels around. Either they will be series wired to high voltage and sent to a string inverter or to a MPPT charge controller and stepped down to charge a lower voltage battery bank.

KD0CAC · September 2018

It's hard to walk away from $00.32 per watt panels , just trying to figure if I could incorporate with my next system .
Not sure what or when , had a fire and lost a lot of panels , charge controller etc.
I did repair the inverter , but would like to upgrade that anyway from the Freedom 458 2512 .
Get into pure sine-wave .
Also into ham radio , so to complicate things , trying to get RFI quite .
Also may build a 18650 lithium power wall .
Thanks

Estragon · September 2018

You might be able to use the panels on something like a Midnite Classic controller. Two in series might be too high VOC depending on your local record low temps for a 150v controller, but a Classic200 should work. Three in series might work on a Classic 250.

mike95490 · September 2018

73Vmp panels on a real MPPT controller would charge a 48V bank fine. But you barely get the real benefit of MPPT unless you series the panels to save on wire size. As was stated before, you need a 200V controller to be able to use those in series.

1st time post - ? about higher voltages 72.9v

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