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Hi I would like to build an island photovoltaic system, I have 1 MPPT 75/15, and 1 12/1200 inverter, 16 125W modules 7.30A - 18.20V, and 6 AGM 12V 100Ah batteries, how can I size my systems, can someone make me a prospectus of autonomy and if the case requires other equipment?
Thank you
6 * 12V * 100Ah * 50% usable = 3600Wh
Your MPPT is limited to 15A * 14.4V = 216W
You can likely over-panel the unit with a 3S2P array (750W), but it will never output more than about 216W due to the 15A current output limitation.
To fully utilize all 16 of your panels, you'll need 167A of MPPT output, so 11 of the 75/15 units.
Estimates of an over-paneled system are hard to make accurately, but I suspect that you'd be able to harness about ~1600Wh/day assuming clear skies and all-day exposure, but this depends on your latitude. "island" drives me to assume something tropical.
In terms of autonomy, that's impossible to say without knowing your demand, but using the estimates above, you could possibly use 1600Wh daily without eating into your reserves. If unable to charge, you could have 3600/1600 = 2.25 days of autonomy assuming you stick with the 1600Wh/day the array would produce.
Note that while 50% is the recommended maximum depth of discharge for good cycle life, in an emergency, you could go as low at 80%. This would be 5760Wh of 1600Wh/day use or 3.6 days.
When figuring your autonomy, don't forget to include the consumption of the inverter itself. They gobble power just by being on, even if no loads. Guesstimating a good 1200W inverter would consume about 10W, so that's 240Wh/day or 240/1600 = 15% of your available solar
which regulator could I replace it with?
Il tuo MPPT è limitato a 15 A * 14,4 V = 216 W
216Wx8h = 1718Wh is correct?
1718Wh is optimistic. I rounded down to 1600Wh.
Something I didn't consider: Your batteries likely can't handle 167A of charging. They are likely only rated for 10-20A each. I'll split the difference and assume 15A, so 6 * 15A = 90A as a target
2X MPPT 100/50 each with 4S2P array on it should allow you to use about 720W on each controller. You'd still be over-paneled by a bit.
What is your location?
Hi @elektro
Different approach. I wouldn't build a system with 6x paralleled 12V batteries. Been there, never again. They slowly develop imbalance and die way earlier than they should.
Consider 24V. Sure, you'd need a new inverter.
But you could then wire 4x of those panels (2S2P) into the existing 75/15 and double it's output to 432W (of the nameplate 500W pv).
The remaining 12x panels (1500W) into a new 100/50 mppt (3S4P or 4S3P). 50A @ 28.8V = 1440W.
And if you have 12V loads, a 24/12 Orion converter(s) for those.
Do the sums. The existing inverter will have a used value, and your mppt expense much reduced. Smaller wiring needs. And I bet your batteries will last longer.
