Step 1 Done converting to 24v system

Re: Step 1 Done converting to 24v system

Z,

I am not sure what got you upset?

In any case, what we try to do is balance needs against the battery bank, and charging source(s) against the battery bank too.

Batteries that do not have sufficient charging sources and/or more loads than charging energy available will tend to die much sooner.

And, if you have a few days of outage, and no backup charging source (solar, genset, etc.), then the batteries sulfate--And again, may last weeks to a few months.

For solar power, the recommended solar array would be around:

225 AH battery bank * 29 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 423 Watt array minimum
225 AH battery bank * 29 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 847 Watt array nominal
225 AH battery bank * 29 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,102 Watt array "cost effective" maximum

400 Watt array is just on the bottom edge of what we would recommend for an emergency backup system/weekend/seasonal use system.

Similar questions about an AC genset. A small(er) genset with AC battery charger in the:

225 Amps * 5% = 11 amp @ 24 volt charger
225 Amps * 20% = 45 amp @ 24 volt charger

The 5% to 10% charger would work with a smaller (2 kWatt) or so genset. A larger charger would need a larger generator (and more fuel) to keep the battery bank up in longer outages.

Power wise, if you assume 2 days of storage and 50% maximum discharge over 5 hours of discharge per day (or per evening) from your battery bank:

225 AH * 24 volts * 1/2 day storage * 0.50 max discharge * 0.85 inverter eff * 1/5 hours per evening usage = ~230 Watt load over 5 hours per day usage.

And, if you have a 400 Watt array and using Springfield MO for PV Watts (fixed array, tilted to latitude):




Month
Solar Radiation
(kWh/m²/day)


1
3.93


2
4.20


3
5.18


4
5.54


5
5.71


6
5.80


7
5.92


8
5.99


9
5.44


10
4.95


11
3.83


12
3.29


Year
4.99




Assuming something like 4 hours minimum of sun:

400 Watt array * 4 hours of sun * 0.52 system eff = 832 Watt*Hours of "useful" power per average "winterish" day.

So, depending on weather and time of year you get your outages--You could use some generator run time to make best use of your battery bank (another ~400 Watts of panels may be a good tradeoff against buying a genset+gasoline)... Of course, no sun, no solar power, so a genset is needed if you need power during poor weather.

Does this look like the system you envision?

-Bill