What size battery do I need for my solar system

Load = 336 Watt

Voltage = 12 V

Current = 336/12 = 28 A

Battery Capacity = 28 x 5 = 140 AH

So, 200 AH battery seems not bad even considered the other factors (aging factor, design factor, inverter efficiency etc.) but if you can go for 250 AH, it will be much better. The higher the AH rating, the lesser the DOD (Depth of Discharge) of the battery and hence the better is the battery life.

- MS

What solar panel size will be suitable for such load ?

Usage/Charge a little confusing here.

Worst Case Scenario! And this is like homework.

Step One

370W/.90 (just in case it is AC anywhere along the line. Inverter inefficiency loss.)

412W rate need for 8 hours = 3296Wh/d (avg. per day/7 days a week/ 365 days/year)

I must also assume a 12V load and system voltage!

3296Wh/d divided by 12V = 275 Ah/d

Step Two:

A SunExtender 12V PV battery comes at 200Ah.

I also assume you want only one day of autonomy.

275Ah/d x multiplied by 1.59 for the worse case cold conditions x 1 day of autonomy divided by 200Ah Battery capacity and then divided by .50 for DOD (depth of discharge of gel sealed lead acid batteries) = 4.4 batteries. 5 total batteries are needed at 12v will be needed.

At 336w for 5 hours or the best case scenario. 1680Wh/d

1680 / 12V x 1.59 x 1 / 200Ah / .50 = 2.3 Batteries. 3 total batteries

With no cold temperature multiplier:

1680 / 12 x 1 /200 / .5 = 1.4 Batteries. 2 total batteries.

With no cold temp multiplier and a .8 depth of discharge (deep cycle)

1680 / 12 x 1 /200 / .8 = 0.875 Batteries. 1 total battery.

Assuming you want a charge rate of C/8, you will want a array to produce all total amp-hours in one day.

If we use the last battery calculation of 1 battery and 1680Wh/d, here is the array spec you will have to meet after all losses:

140Ah/d capacity of battery divided by 8 hours of charge = 17.5A/h at 12V nominal array will be needed to charge the batteries. (8 hours x 17.5 x 12v = 1680Wh/d.) C/8 may not be a safe charging amount for a gel. I don't quite understand your initial specs.

Good Luck.