Smoking

Re: Smoking

My/our pleasure Landon. I always try to remember what it was like when I was young/first got started in engineering... Always had too many questions myself. :roll:

Please let us know how everything works out for you.

-Bill

Re: Smoking

techcord wrote: »

Okay, new question, I have:
2 X 12v Deep cycle 92 amp batterys, flooded.
ProStar ps-30
300w 24v inverter
4 hours a day of sun light.

What 24v solar panels do I need for this setup?

OK, here are some "random" uses of rules of thumbs:

24 volt @ 92 AH battery bank. The solar array needed to recharge such a bank would be (based on 5% to 13% rate of charge):

• 92 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 173 Watt array minimum
• 92 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 346 Watt array nominal
• 92 AH * 29 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 450 Watt array cost effective maximum

A 30 amp PWM controller would use around (always refer to manual for exact numbers) a maximum array of:
30 amps * 35 volts VMp = 1,050 Watt array maximum (just a guess)

The panels to use would have have Vmp in the range of 17.5 to 18.6 volts or so times 2 in series. Or single panels with Vmp in the 35 to 38 volt range.

Generally, it is better to use a few large panels rather than a bunch of small panels (less electrical connections, less mounting hardware, etc.). Two or four of these "12 volt" 140 watt panels would be nice for a 24 volt system on a pwm controller.

Normally, we suggest 1-3 days of energy storage and 50% maximum discharge for a battery bank. A 2 day system with 50% max discharge would suggest using ~25% of the battery capacity per day. For a 24 volt @ 92 AH battery bank:

• 24 volts * 92 AH * 0.25 = 552 Watt*Hours at 24 VDC per day nominal
• 92 AH * 0.25 = 23 Amp*Hours at 24 VDC per day nominal
• 24 volts * 92 AH * 0.25 * 0.85 AC inverter eff = 469 Watt*Hours at 120 VAC per day nominal

With 2*140 watt solar panels and 4 hours per day of sun, your available AC power would be:

• 2*140 Watts * 0.52 system efficiency * 4 hours of sun per day = 299 WH of 120 VAC per day based on 4 hours of sun

And 4 panels would simply be 2x of the above.

If you are looking at a 300 watt AC inverter--I would seriously consider using a 12 volt battery bank and a 300 watt MorningStar 300 watt TSW 12 volt inverter. For small systems, there is probably no better inverter at the price and has the "search mode" and remote On/Off function.

Basically, the same system you are looking at but just putting the batteries and solar panels in parallel instead of series. With 30 amp PWM controller, its array capacity would be 1/2 of the 24 volt Array Wattage.

-Bill