can anyone help with my solar string ?

benewt

I have an off-grid system on an island and looking for some help on string size. Currently I have the system below:
Type watt tot watt VMP VOC Description
8 Kyocera 130 1040 17.6 21.9 kc130tm
8 Mitsubishi 190 1520 24.7 30.8 pvud190mf5
2 Shell 175 350 35.4 44.6
2 BP 80 160 17.6 22.1
Total 3070

FX3048 SEALED Inverter (3KW CONTINOUS)
MX60 charge controller
Outback HUB
Outback Mate
2- Eu2000 in series
8- Trojan L16-RE Battery

currently I have 4 strings made from:
2-3 Mitsu 190
2-4 Kyocera 130.
I would like to install 2 more Mitsu 190, 2 shell 175 and 2 BP 80 into the current array. I am not sure the best way to arrange this array to optimize loss. Is there anyone out there who can help?

Cariboocoot

Re: can anyone help with my solar string ?

You already have mismatched strings on the MX60:

The four Kyoceras in series give a string Vmp of 70.4 whereas the three Mitsubishis in series give you a string Vmp of 74.1 - this is not too far off, but it is 5% and you don't want to go further than that. You can't install the remaining two Mitsubishi panels on the same controller.

So far your array is 2180 Watts. That means you have room for about 1560 Watts.

The two Shell panels @ 35.4 Vmp would make 70.8 which is pretty close to the other strings and would add 350 Watts, leaving room for 1210 more Watts.

The two BP panels @ 17.6 will not be enough in series for a 48 Volt system. Whether or not they could be used in conjunction with the two leftover Mitsubishi panels would depend on the Imp ratings which you don't give. I can calculate them as 4.5 for the BP panels and 7.7 for the Mitsubishi panels; much too far apart to work.

Without getting more identical panels you will not be able to add more to the MX60 other than the two Shell panels. You already have four strings and can add one more. Each of these strings needs to have a fuse or circuit breaker on it suitable for the panels' series fuse rating.

Without the Amp hour rating of the L16 batteries (there are different ratings for the same size case) I can't say how much current you'll need. They could be 320 Amp hours, in which case the existing array should be sufficient. Likewise if they are 390 Amp hours it would be good enough, but would benefit from the additional 350 Watts of the Shell panels. With them you'd have about 40 Amps peak charge current.