Author Topic: Best system setup please help newbie  (Read 3864 times)


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Best system setup please help newbie
« on: May 13, 2013, 05:05:50 PM »
Hi I'm new here. Great site. I have wanting to set up a partial off grid system at home for a while now and have recently purchased 4 170w panels i was only gonna buy 2 but got a bit carried away.  I thought I knew how I was going to set it up but now I have 4 my small time plans have gone buy the way side. So
First thing is the figures supplied on the panel mainly the amperage seems really low for such a large panel at ( have attached pic). Primarily I want to run all the lighting  in my house on 12v so room by room as I go round the house I am rewiring for the new system with 12v cable and led mr16 down light mainly.  which are 4 watt so decided by12 makes .33amp per bulb so I have8 down lights in my kitchen which total 2.66 amp. So eventually when I have run this system all the way through the house I will have a max of 70 down lights which should be a grand total of 23.33 amp and a few led stip lights poss 4amp so let's say 30amp per hour if every light in the house were left on ( which obviously should never happen ) I am also installing a 12v charging system around the house for phone charging and other small electronics and installing a 12v vehicle sound system in the kitchen and lounge. PEASE LET ME KNOW IF MY CALCS ARE OFF. So now I have more and larger panels than I expected I would like to try a to build a system that is at least temp for short times off grid or even run some of the smaller electrics in the house of grid more permanently.
So I'm thinking that I need a 60w solar regulator mppt as I divided the170w of the panels x12v and got 14amp so I'm guessing this is not how to work this out as it says 4.86 on the panel ( this is confusion at the start )so now do I only need a 20w regulator/cc? Any way I am then going to charge a bank of batteries not sure how many poss about 400 ah but don't know if I can go higher. I then intend to run all the lighting and the charging sockets and radio ( all individually fused )off the batteries and if poss an inverter to run other small stuff. SORRY I'VE DRAGGED ON FOR SO LONG. So here's a couple of ?s
Would it be best to run the panels into the regulator / charge  controller in  parallel 12v or in series poss 24 or 48.
If I do run it in the higher v do I then need to put the batteries in parallel to get 24.
If so what voltage will come out of the load terminals 12/24/36or 48 as you can tell I thought I knew what I was doing but have got myself a little/lot confused. I'm so sorry if this all seems like gobbldy gook but I could really do with some help thanks toby


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Re: Best system setup please help newbie
« Reply #1 on: May 14, 2013, 12:55:22 AM »
The panels are meant for a series system, or for a 24V battery pack. Best is to get a MPPT controller that can handle 700W or more, though Kibi is the one as he has installed a controller that can do this. Look at his posts and see which one he has used.


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Re: Best system setup please help newbie
« Reply #2 on: May 16, 2013, 02:20:22 PM »
Hello Toby

I read this thread after I answered in your other thread. This thread provides much more information, so I can give you a better answer here.
I assume you got those panels from Bimble Inn? That is an extremely good price. The panel says 4.86A at 35V. This equates to 170.1W. The 35V, 4.86A is the Maximum Power Point of that panel. Don't worry about the battery voltage, that panel will never supply 14A on it's own. However, an MPPT charge controller between the battery and the panel will however do some power conversion and will enable the battery to realistically charge at about 10A (120-140W depending on the battery charge state) from one panel. That includes power losses in the controller. Don't expect to ever see the full 170W from the panel. This rating is the manufacturer's STC rating (Standard Test Conditions). The NOCT (Normal Operating Cell Temperature) rating of your panels would probably be in the 140W range.

Now, with that many 12V loads you will definitely need a 12V battery system and you will definitely need a MPPT charge controller. Bimble Inn do a reasonably priced MPPT controller like this one, but do not quote me on the quality of this unit, I know nothing about it other than it's attractive price. Although more expensive, I'd recommend an Outback, Victron, Morningstar or Midnite controller. Bimble Inn sell Outback charge controllers at reasonable prices. Go for the FM80 if you can afford it. I got the Midnite Classic because it is more powerful that the Outback FM80 both in terms of charge power and communication facilities (I am a data logging freak).

If your site doesn't suffer from shading, then I'd recommend wiring your panels in two strings of two series connected panels. Unfortunately, this will be about the limit of a FM60 controller on a 12V system. The FM80 may be able to support six of your panels in two strings of three (1020W STC) if you wish to upgrade to more power at a later stage. If some of your panels may be shaded at certain times of the day then go for all four in parallel via a combiner box.
1KW seems like not a lot of power for an expensive charge controller, but this is the limitation of a 12V battery system. You'll have to add another charge controller if you want more power. The FM80 would support 4KW of panels if you had a 48V battery system. The charge controller is limited by it's battery charge current. For example, if the charge limit of a controller was 100A, it could charge a 12V system at 1200W and a 48V system, also at 100A charge current, is 4800W.

I don't think a DC-DC converter for higher battery voltages would be practical in your situation since you already have so many 12V loads. 12V is a very efficient way of doing things as you are reducing or eliminating power conversion processes and the current through the loads is not too high to worry about power losses in the cables.

Please refer to my thread here for wiring and safety suggestions:


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Re: Best system setup please help newbie
« Reply #3 on: May 17, 2013, 05:41:42 AM »
Wow you know your stuff thanks very much if you get a chance I have asked a bit more of your knowledge in my other thread thanks Toby