Used Hanwha 305 panels?

Re: Used Hanwha 305 panels?

Welcome to the forum retep!

About your battery bank, you have one bank for both vehicle and RV (House) power? That is a bit unusual--Generally having a separate vehicle battery bank allows you to still start the battery if the house bank was taken dead/very low. And many larger "bus" type applications use 24 volts for the vehicle battery.

Second, do you have a power estimate for all your house loads? That sounds like a lot of power from a, relatively small, battery bank.

Anyway--Some numbers (assuming you want to do dry camping and live near full time off grid and don't drive it "that much"--i.e., many days/week+ between trips--mostly solar power).

The battery bank, maximum discharge to 50% (for long life and so you can, hopefully, start your vehicle motor). Assuming 12 volt battery bank, that should be around 660 AH at 12 volts. 25% to 50% discharge per day (for an off grid cabin, we would recommend around 25% discharge per day, 2 days of storage, to 50% maximum discharge):

• 660 AH * 12 volts * 0.85 inverter eff * 0.25 discharge = 1,683 WH of 120 VAC power per day
• 660 AH * 12 volts * 0.85 inverter eff * 0.50 discharge = 3,366 WH of 120 VAC power per day

Next, we size the solar array two different ways... First based on battery bank size, second based on loads (and amount of sun in your area).

Based on battery bank size, 5% to 13% rate of charge. 5% is good for weekend systems, 10% or more for full time off grid systems:

• 660 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.05 rate of charge = 621 Watt array minimum
• 660 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge =1,243 Watt array nominal
• 660 AH * 14.5 volts charging * 1/0.77 panel+controller derating * 0.13 rate of charge = 1,616 Watt array "cost effective" maximim

Then there is solar paneling based on your loads... From the "backwards battery calculations (assuming in winter you would use genset, are in a relatively sunny are of the US, 4.0 hours minimum average sun per day):

• 1,683 WH per day * 1/0.52 end to end system eff * 1/4.0 hours of sun per day = 809 Watt array minimum
• 3,366 WH per day * 1/0.52 end to end system eff * 1/4.0 hours of sun per day = 1,618 Watt array minimum

Note that solar panels in the US southwest can be mounted flat to roof in the summer for pretty good power collection. However, go north/winter operation, you may need to tilt the panels to 45 degrees or more vertical for winter operation. Note--In bad weather areas (coastal fog/marine layer, winter), you may get 2 hours of sun per day or less.

The 12.5 kWatt genset--Probably 2-3x the size that I would need to run my whole home. You might want to look at a smaller genset (4kWatt or smaller)--Conservation is going to be your friend here.

Simimlar with your 2.5 kW and 1.8 kW inverters--Practically speaking, that battery bank is really only capable of running the 1.8 kW Xantrex Prosine at full power. Anymore than that, the battery bank (as currently configured) would not be able to supply any more power reliably.

I would suggest that you size the loads (and your expectations) to run from the 1.8 kWatt inverter only. Everything else would need to run from the genset/shore power.

Will stop here... Lots of numbers and assumptions. And enough information to move the discussion forward.

Questions/updates to my guesses?

-Bill