75V Solar Panel with 12V Battery System

[UFO]

I have space for 1 more solar panel and I have found a 390W that fits perfectly.



I already have 600w running on a MPPT and would install this one on its own MPPT.


Link is:


https://www.solaronline.com.au/390w-...lar-panel.html


Questions are:


1) As its 75V will it be very inefficient going down to 12V?


2) Should I go with a 100V 30A MPPT or 100V 50A MPPT?



3) Is there anything else I should be considering when running two separate solar arrays into the same battery bank?

[SVHarmonie]

Originally Posted by UFO

I have space for 1 more solar panel and I have found a 390W that fits perfectly.

I already have 600w running on a MPPT and would install this one on its own MPPT.

Link is:https://www.solaronline.com.au/390w-...lar-panel.html


Questions are:
1) As its 75V will it be very inefficient going down to 12V?
2) Should I go with a 100V 30A MPPT or 100V 50A MPPT?
3) Is there anything else I should be considering when running two separate solar arrays into the same battery bank?

1 There is no significant penalty for a high voltage panel feeding a properly designed and functioning MPPT as long as the peak voltage is within the MPPT design specification. Check this to be SURE. Higher than design voltage will fry things.

2 Most MPPT controllers that I have used don't care if the amperage available is higher than what they can supply. They just "throw the extra away". A 30 Amp rated MPPT controller will--on bright sunny days--occasionally run in to the limit with the panels you describe and max out at 30 amps. If you want every possible coulomb out of the panels, then the 50 amp MPPT unit will be needed. Only you can decide if the extra cost is worth it.

3 Nope. The controllers will play happily together. It is a common misconception that multiple charging sources will somehow "fight each other" or "conflict." They will not.

[noelex 77]

Originally Posted by UFO

1) As its 75V will it be very inefficient going down to 12V?

No. The conversation efficiency will be a little worse, but the effect is minor.

Originally Posted by UFO

2) Should I go with a 100V 30A MPPT or 100V 50A MPPT?

The 30A model will only very occasionally run into its maximium current so it should just be OK. If the 50A model is not much more expensive it will run cooler and will avoid the controller relying on its self protection mechanism to limit the current.

Originally Posted by UFO

3) Is there anything else I should be considering

The Sunpower panels are excellent. The high effeciency really helps on a boat where space is limited.

75v DC is a potentially lethal voltage. You need to have very high electrical standards, especially around water. It is also hard to find marine components such as fuses, circuit breakers rated for these voltages. Check the voltage rating of all components between the panel and regulator.

[UFO]

Thanks Everyone

[Wild Goose]

I was looking at those high efficiency panels from sun power myself. I just found the REC Alpha series panels the other day (specifically the 380w), similar numbers, lower voltage and broken into 6 strands for better performance if partially shaded. Don’t know if you have come across them but definitely worth a look. Also the price I got was about 30% less than the sunpowers.
https://www.recgroup.com/en/alpha

[UFO]

Originally Posted by Wild Goose

I was looking at those high efficiency panels from sun power myself. I just found the REC Alpha series panels the other day (specifically the 380w), similar numbers, lower voltage and broken into 6 strands for better performance if partially shaded. Don’t know if you have come across them but definitely worth a look. Also the price I got was about 30% less than the sunpowers.
https://www.recgroup.com/en/alpha

Thanks - They look good. Very slightly bigger than the sunpower, I'll need to see if I could squeeze it in.


Where did you buy them from?

[Wild Goose]

I haven't got them just yet, still finishing the mounting frame. I spoke to a sparky I had on my jobsite who installs solar on the side, just got me the pricing from a wholesaler.

[UFO]

Originally Posted by Wild Goose

I haven't got them just yet, still finishing the mounting frame. I spoke to a sparky I had on my jobsite who installs solar on the side, just got me the pricing from a wholesaler.

Got the REC Alpha 365W today for Au$335. Couldn't get any higher W as the higher panels are in limited supply due to limited imports because of the virus.