Need Help, I am a little confused.

[Matrix]

So we have.

TV 70w x 5 hours = 350wh
dishnetwork 12w x 5 hours = 70wh
Refrigerator used .8KWH or 800wh in 24 hour period. = 800wh
Lights 2 of them (13x2) = 26 * 6 hours = 156wh
Fan 100w x 10 hours = 1000wh

The only load that must be running ideally is the refrigerator. Taking those numbers into consideration, how many 100 watt panels should I shoot for? 10 of them will be a total of 5000wh in a 5 hour period. that exceeds the maximum daily allowable usage by almost double. That should give me extra power on sunny days, minimizing my overall needs from the battery bank.

How much more of a savings is 250w panels? I paid approx one dollar per watt with free shipping.

Using your daily need of 2300 wh's and using 4.3 as the total hours of sun exposure with 1 day autonomy , at 100 watts per panel I am seeing you need 700 watts per day from the array to recharge the batteries. Everything more than that is gravy or excess power that could be used to run stuff in the day . I am getting this from the Alte Store Off grid calculator that you could search for on the web and mess with the numbers yourself.

[Mike90250]

from sunelc.com - half the price/watt you paid.
Astronergy 250 Watts
Location: Miami
Model: ASM 6610P-250
Qty: 22
Pallet Price/W: 0.48
Single Price/W: 0.55
Modules/Pallet: 22
specs sunelec.com/ASM6610P_250_260.PDF 30v panels

Assume any panel will only produce 70-80% of nameplate
Assume batteries need 1.3 x what was taken out, use 100Ah, recharge with 130Ah
Inverters have loss, figure 20%
Charge Controllers have loss -MPPT stage 95% eff

Mornings and Afternoons, sun angles are bad and you may only get 50% of nameplate +- 1 hour of solar noon is the peak production time.

I suspect your 800wh fridge usage is, over a year, going to be low, few fridges can run below 360Kwh / year

[Soho]

Lets hope you have not bought all the panels yet.. you can save $ by using 250W grid tie panels, and let the MPPT controller, down convert the panel voltage to battery voltage.

So, in winter, you have a cloudy day, followed by a sunny day. and need to both recharge batteries AND run your normal daytime loads
easiest to count in watt-hours, if you burned 3600wh on a cloudy day, and plan on another 3600 of loads, and recharging
that's 7200wh x (about 30% losses) or 9360wh you have to harvest in your 4.5 hours (you sure are optimistic) - you would need about 3Kw of panels, and that's cutting it close (remember panels only give you 80% of nameplate under normal conditions)

Thanks for the reply Mike. I want to ensure I understood your response. Are you saying I need enough panels to cover little over the full capacity of the batteries? In my case, 100 watt panels were all I could get to Puerto Rico at no additional cost.

Can you look at my specific case again, I think the way you calculated consumption in my case was broad and I explain. My four 6v batteries can only hold a maximum of 5280wh. Of which I can only use a maximum of 2640wh. On my original post, I did not mention consumption, I will do that now in order to provide a clear picture. The main load will be a refrigerator, It is small and uses 100w when running. Led television utilizes 70w, a dish network DVR 12w. Other than that it will be lights "they are all LED" 13w each. Fan 100w.

So we have.

TV 70w x 5 hours = 350wh
dishnetwork 12w x 5 hours = 70wh
Refrigerator used .8KWH or 800wh in 24 hour period. = 800wh
Lights 2 of them (13x2) = 26 * 6 hours = 156wh
Fan 100w x 10 hours = 1000wh

The only load that must be running ideally is the refrigerator. Taking those numbers into consideration, how many 100 watt panels should I shoot for? 10 of them will be a total of 5000wh in a 5 hour period. that exceeds the maximum daily allowable usage by almost double. That should give me extra power on sunny days, minimizing my overall needs from the battery bank.

How much more of a savings is 250w panels? I paid approx one dollar per watt with free shipping.

[Mike90250]

Lets hope you have not bought all the panels yet.. you can save $ by using 250W grid tie panels, and let the MPPT controller, down convert the panel voltage to battery voltage.

So, in winter, you have a cloudy day, followed by a sunny day. and need to both recharge batteries AND run your normal daytime loads
easiest to count in watt hours, if you burned 3600wh on the cloudy day, and plan on another 3600 of loads, and recharging
that's 7200wh x (about 30% losses) or 9360wh you have to harvest in your 4.5 hours (you sure are optimistic) - you would need about 3Kw of panels, and that's cutting it close (remember panels only give you 80% of nameplate under normal conditions)

[Soho]

Hello all,

I understand the gist of how to calculate the size of the system "based on actual consumption". Where I am confused is the ration of solar panels to the battery bank. Allow me to explain where my confusion lies. Let's suppose that my battery bank will consist of four 6v batteries. The batteries will be wired in serial to make a 220 amp hour 24v bank. The batteries will be flooded lead batteries. Based on my understanding I should not go below 50 percent of the capacity and less and no less than 70 percent is preferred. So with that in mind 220AH * 24 = 5280 then 5280/2= 2640. So now let us say I want to install 100 watt 12v panels wired in pairs to make them 24 volts. How many panels should I install? For purposes of this exercise, let's assume that I will get 4.5 hours of Sun. Do I need enough panels to cover the 5280 watts over a 4.5 period of time? or do I get just a little more than the 2640 watts? I was considering using eight panels. Please help me understand the proper way to size the panels to the batteries.

Also let's assume that the equipment is already purchased, changes at this point are not possible. The only decision that can change at this point is the number of panels. At some point, I would like to add 4 more 6v batteries. The controller is 40 amps and it is MPPT, the panels themselves are Mono.


Thanks.