Backyard Aquaponics
A place to discuss aquaponics

Hi all, I have been spending a lot of time researching 12 volt systems and solar for my camper and as a consequence have taken on the Perth agency for Mandrakes Solar Power.

Apart from complete kits with controllers fitted to them as sold in many camping stores, I will also be holding stock of various sizes of monocrystaline modules/panels. These are perfect for maintaining 12 volt battery banks used in conjunction with fallover switches for battery backup as well as any other solar system you might want to set up. You will also find the prices are cheaper than most of the other gear around and the quality is excellent.

If you are interested check out the site and drop me an email with any queries you might have.

www.solarsteve1950.com

Cheers,
Burnsy

there is often talk of running systems off the grid and Arbe contacted me interested in doing it. running his system off the grid completely. I am really keen to have a go at doing this but initially I did not think it was really feasible however I have now done some tests and here are the results.

The Belkin 300/600watt inverter coupled to a 35 watt Pondmax PU3000U pump drew a constant 3.75 amps together.


This was the power supply, 124ah worth of 12 volt deep cycle batteries running to the inverter.


Overview of test.


Based on my calculations, with 160 watts of solar power and 210aH worth of deep cell batteries you could run this pump for 28 days in cloudy contitions before it reached 40% drawdown on the battery. During sunny weather it would run indefinitely. It would need to be field tested but there is a chance that during perths winter we get enough sunny days to run through, you would however need to keep an eye on it and possibly hook up a charger if things started looking bleak.

Cost for the solar side of this would be $640 for panels and $100 for a 20amp MPPT regulator. On top of this you would need an inverter and batteries. Cheapest option for batteries would be a bank of used scooter batterys such as I have done in the school battery backup system.

The other thing you would need is a 12 volt timer to run your 15/45 pumping regime as the inverter draws around 0.3amps by itself so you would not want that running 24/7.

If anyone wants a copy of the spreadsheet I used to do the calculations so they can have a play with it pm me your email address.

Sorry about the first paragraph in that last post, family crisis meant I had to push submit before I had finished editing

I'm definately keen. Do you have a payment plan?

Seriously though, I am saving my pennies so I can take my system off line with mains power being the backup plan.

How efficient is the inverter you were using?

My calculations, not including the solar panel, say the battery will only last 9 days and depending on your charger could take days to re-charge.
Anyway a pump that size running 15 minutes per hour will only cost you about $16.00 per year to run, you would never get your money back when you factor in battery replacement etc.

Any luck finding a 12 volt timer though Burnsy? Thats were I fell down with our solar system..

I really don't kow much about inverters but figure belkin is a decent brand and it was only a little one as you can see so you are not likely to save much on efficiency unless you are running some huge inverter that is not needed. Most of the energy usage from the inverter I would guess to be from the cooling fan.

Start collecting second hand batteries now - they are the big expense if you buy new and we will make it work.

Not even 9 days Aquastud, 5.6 days and you are at 40% of battery capacity. Unless you have money to throw away on new batteries (around $350 for a 105aH unit) I would not be going to that low very often. Ideally you want to stay above 60%.

I don't think anyone would do this for a cost saving. It is purely beacuse they either, don't have access to grid power or like the idea of doing the solar thing.

Can't say I have looked EB but they must be around somewhere.

You also have to consider your investment in your fish.

I have 100 trout. Let's say I am growing them to sell at $10 each but a power outage means they all died....

In my case I plan to move out to my country block which will be totally off grid.

With an inverter you wouldn't need a 12 volt timer. A standard timer would work.

They would have to have 12 volt timers for boats, camper vans etc. If not then there are 12 volt timers for defrosting 12volt fridges.

Yeah but the timers are a bit power hungry..

We just bought a new deep cycle battery for our solar system which had been running plugged in for quite a while. Got it back on solar but within 2 days there was low battery alarms screaming.. I discovered someone had changed our pump from a 20W to a 65W and I didn't know, plus the air pump had been left on.

I'll try again in a few days after it's had some time to recharge the battery, see if I can't find the low wattage pump again.

I'll do some searching for timers, wasn;t easy to find a simple one with enough on/offs a couple of years ago..

Correct you could use a standard 240 volt timer but the small inverter I used draws 0.3 amps so to get the best efficiency you would want to only have it on when the pump is on. 0.3 does not sound like much but it adds up, nearly 2aH a day it would use when it was not required to be on. Also there is the extra wear on the inverter and its fan from having it run 24/7.