Off grid connection for a shed.

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Re: Off grid connection for a shed.

Postby Bthree » Sun Jun 07, 2015 8:03 pm

Grakat wrote: I can run my camping fridge on 12v using a 24v to 12v step down unit. School is still out on the inverter. Still working out the difference between an inverter charger and a straight inverter.

I know it's putting the first bit last, but the loads I am looking at are as follows.
12v camping fridge running 24hrs/day approx 4A/hr.
24V LED lighting.


Are you sure the camping fridge can only accept 12volts in on the DC side input, some will run on 12volt to 24volt and could be directly connected across a 24volt supply. Maybe a link to your fridge or a make and model would clarify ?

24v LED lights... there is another thread here somewhere but most 12volt LED lights designed for domestic use actually have an internal constant current PSU and can be run on 24volt direct but only use a fraction more power
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Re: Off grid connection for a shed.

Postby Grakat » Sun Jun 07, 2015 8:30 pm

Hi there,

I have two camping fridges to choose from. One is a Waeco CF50 VERA which has done around 10yrs of sterling work, the other option is an ARB 47L fridge. I will check them out and see if they are ok for 24v. Could save some wiring.

Edit: Just checked, the latest CFX50 can run 12v or 24v, I would assume it's more efficient on 24v.

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Graham
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Re: Off grid connection for a shed.

Postby Bthree » Sun Jun 07, 2015 9:04 pm

ARB fridge https://www.google.com.au/?gws_rd=ssl#q ... dge+manual

WACO not sure about this one
http://www.google.com.au/url?sa=t&rct=j ... xQ4EnkxsNQ

From the spec runs on 24V and draws 3amps when running

Assume the fridge could run for 10 hours in a day, this equals a battery draw down of 30AH which is aprox 14% of your battery capacity
Network = Powercor .. Retailer = Origin .. Installed Christmas 2008
Latronics PV-1200 feed by 8xTrina TSM DC-01 .. 170watt = 1360watts DC in .. 1096watts AC out .. 5+years later 990watts ac out
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Re: Off grid connection for a shed.

Postby Grakat » Sun Jun 07, 2015 9:46 pm

That should work ok for what I want to do. This will serve as an interim measure until the 230v side gets more established.

Do you think the Outback Kid is an ok place to start or should I consider something bigger? I am considering starting off with 2x 200w 24v panels in an East West config, but will build my combiner boxes to take 2 panels each, with adequate wiring for both panels from each combiner box to the charge controller. If the 4 x 200W is too much for the kid (which it is by about 2A) I could parallel another Kid for 60A total.

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Re: Off grid connection for a shed.

Postby Gordon-Loomberah » Sun Jun 07, 2015 10:16 pm

Each panel in a string has to face in the same orientation. Parallel panels/strings can be in different orientations. With the panels facing over 100 dgrees apart as a virtual tracker, there wont be any problems with 4 X 200W panels, as the Midnite Kid will only be outputting about 20A max.

How much can you buy a Kid controller for?
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Re: Off grid connection for a shed.

Postby Grakat » Mon Jun 08, 2015 8:45 am

Hi Gordon,

The kids are available from a few suppliers online around the $650 mark.

I have previously read your thread on virtual tracking hence the idea to get a more consistent output during the day. I also remember that you needed to allow for the total output of the panels through the controller or youll let the majic smoke out.

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Graham.
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Re: Off grid connection for a shed.

Postby Gordon-Loomberah » Mon Jun 08, 2015 12:30 pm

$650 is quite expensive for a 30A MPPT controller, I should have some new Outback FM80s (80A) listed soon for not a whole lot more than that in the 2nd hand for sale section. They'll do 12, 24, 48 and 60V batteries, and work well with Lithium too, as the voltage set points are adjustable.
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Re: Off grid connection for a shed.

Postby Grakat » Mon Jun 08, 2015 2:31 pm

Hi Gordon,

That sounds good. If you could let me know when they become available we will talk. I am convinced at this stage a quality charge controller will be essential. Also plenty of room to add PV panels as it grows.

Will now go and download the manual for the FM80 and learn how to drive it.

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Re: Off grid connection for a shed.

Postby Grakat » Tue Jun 09, 2015 10:55 am

Hello again,

A quick question. For the proposed virtual tracker arrangement, can I run it through one controller, like the FM80 or do I need to have two controllers.

My thoughts at this time is to have four 200W panels in total, with 2 on the east roof and 2 on the west roof. By setting up each pair in parallel that would keep the voltage down, and supply around 16A per pair, for a total of 32A (which wouldn't be achieved due to the orientation). Or is it better to put each pair of panels in series, and let the MPPT controller deal with the additional voltage?

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Re: Off grid connection for a shed.

Postby Gordon-Loomberah » Tue Jun 09, 2015 11:22 am

At 24V, one FM80 will be fully utilised with about 2.5kW of North facing panels, but only in the middle of the day. With 2 arrays of panels 120degrees apart it could handle ~4kW (need to be sure input current can't exceed 64A), although the regulations wouldn't allow that many panels, because the authors probably haven't thought about arrangements like the Virtual Tracker.
4 panels will be fine.

Definitely have each string of panels as 2 in series, which will give an operating voltage of ~65V, thereby reducing losses in the cables back to the FM80. 8A has 1/4 the losses of 16A. The FM80 will handle Voc (for 72 cell panels) easily.
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