Hello from L.A. Lower Alabama

chapy · December 2012

Let me start off with what i got. I have two 60 watt panels, a sunsaver 10L, one 75 AH battery, xantrex sw600 watt inverter, Getting ready to install.
1. Would i be able to add one more 75AH Battery. A total of 150 AH`s if i was only drawing it down 50% to like 75AH`s would i be able to recharge it back up on a good sun day.
2.Do i need a fuse,breaker [what size] or just a disconnect between panels and controller.
3.Is a 10 amp inline fuse between controller and battery the right size.
4.What size fuse between inverter and battery a 50 or 60 amp. [or what size]
5.[Grounds] Grounding lugs from panels to 8`grounding rod. What about inside can i run a ground wire from inverter and charge controller to the same 8`grounding rod out side. The panels and equipment are only 5`apart.

Cariboocoot · December 2012

Re: Hello from L.A. Lower Alabama

Welcome to the forum.

1). What you have there are two panels capable of about 3.4 Amps (check the Imp rating) each, or 6.8 total. For one 75 Amp hour battery that's 9% peak charge rate, which is good. For two 75 Amp hour batteries it drops in half, and falls below the 5% recommended minimum. Could be dicey, that. You'd probably see 30-ish Amp hours max from the panels all day; okay for one battery at 50% DOD but it isn't likely to work for two.

2). You only have two panels in parallel on the controller; no fuse is needed.

3). The 10 Amp fuse on the controller's output is probably adequate considering the current from the panels will never be that high. If you were to "max out" the controller (add a third panel) then you'd need a larger output fuse: 15 Amp. You should then also put fuses on each panel on the input.

4). The inverter at 600 Watts can draw 50 Amps. At minimum Voltage and maximum output this will be higher. The manual that comes with the inverter should have a recommended fuse size. Don't be surprised if it is 80 or 100 Amps. If you know the inverter will always run below maximum you can use a smaller fuse. Otherwise it will blow at inconvenient times. Don't scrimp on the wire size.

5). Yes you should run the grounds to the same rod.

Was that any help?

chapy · December 2012

Re: Hello from L.A. Lower Alabama

Hello from L.A. again

So if i added another 60 watt panel that still would not be enough for a 150 AH`S. I would proably need a total of four. Right
And yes you have helped and answered all of my questions thank you. CHAPY.

Cariboocoot · December 2012

Re: Hello from L.A. Lower Alabama

Depending on what the actual Imp of the panels is and how good the sun, three would be a "maybe" and four would be "on any good day".
But four, if the Imp is 3.4 like I think it is, would be over the limit of the Sunsaver 10 Amp controller: 4 * 3.4 = 13.2 Amps.

Three would be 3 * 3.4 = 10.2 Amps, which would be fine on that controller. With 10 Amps available you'd have a peak charge current potential of 6.6% on 150 Amp hours. Given good weather and no loads drawing while charging it would work. But you probably wouldn't want to take the batteries below 25% on a regular basis.

This isn't any absolute, just the shortcut way of figuring a balanced system that will work in most cases:
10% of battery Amp hour capacity as the potential peak charge current and 25% maximum DOD.
So ideally for 150 Amp hours you'd have a 15 Amp peak potential charge current and 37.5 Amp hours to work with.
If you get more sun, you can go to a deeper DOD. If you get less, you need even more panel.

Weather being the unpredictable thing it is, allowances have to be made for local conditions.

Photowhit · December 2012

Re: Hello from L.A. Lower Alabama

So LA, what are your loads? That's where we usually start.

I use to live in Tallahassee, have fond memories of wandering LA looking to rob someone across a pool table. Wandered as far as Troy, and Eufaulla on bicycle. Even made it to Montgomery and "Slapout" once. Pretty area.

chapy · December 2012

Re: Hello from L.A. Lower Alabama

Photowhit wrote: »

So LA, what are your loads? That's where we usually start.

I use to live in Tallahassee, have fond memories of wandering LA looking to rob someone across a pool table. Wandered as far as Troy, and Eufaulla on bicycle. Even made it to Montgomery and "Slapout" once. Pretty area.

Well we have a small cabin deep in the woods on 40 acres with no power. I would like to add three 3 watt led light
on the front and back porch and one inside, will only be running them when needed. Also a 12V outlet for phones
mp3,AM FM radio,and a portable DVDplayer i know i can run all of this with a 75 AH battery i woud like to add in a
20 watt tv and be able to watch two or three hours a night.

niel · December 2012

Re: Hello from L.A. Lower Alabama

it's not a question if you can run that stuff with a 75ah battery, but more a question of for how long. we recommend not exceeding the 50% dod point to help preserve battery life so that means you have 75ah/2=37.5ah useable and at 12v that's 37.5ah x 12v = 450wh useable. if you can keep it under that per day it could work for you, but that depends on what loads you run and for how long. going with the 37.5ah the charge needed by the batteries by solar will have a limited time that the charge will be available. let's make it 4hrs of good sun over the day to just account for off times of the year or clouds and you get 37.5ah/4hrs=9.375a for each hour needed by the batteries or a c8 rate of charge at 12.5%. this could've been done with the watts as well, 450wh/4hrs=112.5w. doing this with the watts and taking into account efficiency losses and unrealistic stc pv ratings at an average of 77% then this will represent a need of 112.5w/.77=146.1w in stc rated pvs and that's a good starting point minimum.

Hello from L.A. Lower Alabama

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