# Fuse help on small solar setup.

Registered Users Posts: 1
I know this has to been asked 100 times but I want to make sure I got it right.
2 - 100w panels wired parallel.
1 -2000w inverter
1 -12v 100ah battery
1 - 20a charge controller
So from what I gather I need a 30 amp fuse between the panels and the charge controller. I need a 20a fuse between controller and battery and last I need a 200a fuse between battery and inverter. Is this correct. Sorry I am new so if i left something out in the description please let me know.
Thank  you
Kyle
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Welcome to the forum Kyle2st, your 100 AH battery (assuming a flooded cell Lead Acid) can, at best, supply about 20% of its AH capacity for any length of time. I.e.:
• 100 AH * 0.20 (C/5 rate of discharge) = 20 Amps continuous max suggested
• 20 amps * 12 volts = 240 Watts
• 2,000 Watts * 1/0.85 AC inverter eff * 1/10.5 battery cutoff = 224 Amps
Or if the battery were capable of such high current (Some AGM and Li Ion batteries may be able--But not many), would take the battery bank dead in less than 30 minutes:
• 100 AH / 224 amps * 60 min/Hr = 26 minutes (an in reality, at high discharge rates AH apparent capacity goes down)
And a 200 Watt solar array, would take days to recharge a 100 AH battery bank from "dead" to full (and you should never take a lead acid battery to "dead"):
• 200 Watt array / Vmp~18 volts = 11.1 amps in full sun
• 100 AH / 11.1 amps = 9 hours of full sun
Most places get between 3-5+ hours of sun per day--So you are looking at 2-4+ days to fully recharge.

I suggest that a 2,000 Watt 12 VDC AC inverter would need an ~800+ AH Lead Acid battery bank @ 12 volts minimum to run somewhat reasonably, and a 1,200 to 2,400+ Watt solar array...

Regarding fuses/circuit breakers, I would suggest that you take the planned maximum current, and use the NEC derating factor of 1/0.80 or 1.25x against fuse/breaker ratings to prevent false trips (generally a breaker/fuse will not trip at 80% of rating, and should trip at 100%+ of rating).