Adding new PV modules

[PKsolar]

Good day Everyone!

My electrician Bro has grown his system so I gave him my Classic 250 and took his Classic 150. Now I have room for 5 more modules. However... My two parallel arrays consist of 10 (2x) 5 215W Evergreen Spruce models made in MA oh so long again. Hey, that was only 7 years ago. So now I'd like to get something close to the same rating. If I'm off by .5 amps or volts, will that screw up the classic. Would it be better to have the new 5 modules on a separate charger? 48V (8 x 6V US Batteries). If I need another charger, then I'd just go for something new like in the 225-250w range.

I do want to thank you guys for swapping both our classics out when they fried within a month of each other. I'm sure that will never happen again, right?

Thanks for any advice, PK

[Vic]

Hi PK..,

For clarification,  you have 10 of these PVs,  arranged as two strings of five PVs each?

What is the model number of these PVs?  What I did find was the Evergreen ES-E-215-fc3 ...   are these the modules that you are currently using?

Generally when adding parallel strings,  the string Vmp should be within 5% of the string Vmp of the existing PVs,  and if adding PVs in series with existing PVs,  the Imp should be within 5%  --  this would be a good match.  Using PVs that are within 10% is generally considered the upper limit of variation between old and added PVs.

Thanks,   Vic

[Vic]

And,  PK..,

Did a bit more searching,  and,  the PVs that you are probably running are the Evergreen ES-A-215-fa3s,  which have a Vmp of about 18.4  volts,   IIRC.  These would make much more sense for your present strings of five.

If these are the PVs that you are actually using,  the String Vmp would be about 92 V.   So adding 60-Cell (GT type) PVs in strings of three should be quite close to your existing string Vmp.  Most of these newer PVs run at Vmps of about 30 - 31 V.,  which would yield string voltages of about 90 - 93 V at STC.

The  amount  of power per string will be a bit lower than with your present strings of five,  but these 60 cell modules are very common,  and relatively inexpensive.

If you are not currently using a Combiner,  with one circuit breaker or fuse per string,  then you will want to add a Combiner for safety and convenience of troubleshooting,  etc.

Some guesses here may not be correct,  as we will always want more information ...  FWIW,  Good Luck,    Vic

[PKsolar]

Thanks Vic!

Your spot on. It is the fa3s and I'm running the two parrallel wires at 92V and 22 total Amps from a Disco with breakers. Good thoughts. Still trying to search for older models from installers across the country. Storms usually turn up more than a few so I keep hoping. But I don't want to wait too long...

Sounds like you think the Classic 150 can handle a bit of an indifference.
Cheers,
PK

[Vic]

   ...   Sounds like you think the Classic 150 can handle a bit of an indifference.
Cheers,
PK

Hi PK,  thanks for the added info.

YES,  if your calculated String Vmp IS 92 V (and that seems to be the case with your present PVs),  then the Classic should be quite happy,  and not even notice any difference.

Polycrystal PVs  usually have a bit lower Vmp,  than Mono PVs,  and perhaps using Poly PVs  might be slightly better compatibility with your present Evergreens,  but this is probably a secondary effect  --  do not know,  as have never tried combining Mono and Poly PV on the same CC.

Hope that you can find the PVs that you want for your system.

FWIW,  Good Luck,   Vic