Backyard Aquaponics
A place to discuss aquaponics

Nice looking set up there Jamie

Thanks Jt _ not really a setup yet but things are progressing

I took all the good advice and went to see Murrays setup this morning - excellent. His vegies are really thriving.

I can really see the advantage for him (and for everyone else in Australia). Although he lives only 10 minutes out from me its a draught declared area (also about 2 degress hotter!) - everything looks bone dry.

I can see a massive growth in aquaponics from here on in - every backyard will have one - the advantage being it uses far less water than soil gardening.
Which means it's a great opportunity for those who get in early & get the skills to make a business out of this. Not necessarily selling "stuff" but selling knowledge.

I reckon if someone comes up with a kit for a small system - a small tank for 50 fish, a couple of grow beds etc - they will sell well in the future.

Look at what global warming & peak oil is going to do to future society and you'll get my drift.

Cheers
Jamie

Murray gave me a run down on his system (thanks Murray!).

After talking to him what I'm going to do is ensure I have a fall back position in case of power failures. I am toying with the idea of buying a couple of deep cycle batteries, a battery charger and an inverter.

My pool is about 25m from ac power. What I think I'll do is have the battery charger continuously charging the batteries, have 25m of dc wiring down to the pool and an inverter to get it back to 240ac.
So the pump will be running off a "UPS". The length of time it runs during a power failure will depend on the size of the batteries.
At Supercheap they have Bosch 75ah deep cycle batteries for $195.
My pump is rated at 100w (I guess .5ah)

The other alternative is a small generator. But I might not be around when the power fails and Murray tells me his fish were gasping after 1 hour without air.

There are a number of threads discussing backup power Jamie. The sort of thing you are talking about, as well as a generator for you to start up manually in the case o longer power failures would be the go. BTW I got my 75 amp hour Bosch deep cycle battery for $135, also from supercheap.

Jeez :0 Thats a big price difference. What Supercheap did you go to?
Yes - I saw some comments about using old computer UPS's.
What are you doing with your battery VB? What sort of inverter have you got & whats the wattage of your pump?

Cheers
Jamie

All the info is here Jamie VB's Backup

The intention is to get a cheap generator to run the water pumps. Battery backup is just to keep aeration up till the gen can be turned on. Fish should be okay for hours under this system as should the plants.

PS - was the one at Enoggera. Was 10% cheaper than normal due to a 10% off sale on certain batteries, but that doesn't explain that difference. Another one near me had it about $10 more expensive.

jamie, you're probably looking at more like 10 ah.

100W at 12v is 8.3amps

with an efficiency of 85% for the inverter takes you to about 9.8ah

the .5 amps would the current drawn from the 240v side of the inverter, not the 12v side.

by multiplying the voltage by a factor of 20 the inverter draws 20 times the current (at 100% efficiency)

Steve

Jamie,

Before you outlay too much money, get someone to calculate the voltage drop that will occur over 25 metres of 12 volt wiring.

I'm not up on the specifics but I do know that low power systems can suffer serious efficiency problems arising out of voltage drop.

Steve may be able to do the math for you.

muzz would probably be able to tell you off the top of his head what gauge wire to use for a 25m 12V run drawing 10 amps.

Otherwise i can llok it up

Thanks VB, Steve & Gary!
Thanks for the link VB. Everyone seems to have addressed all of my problems but you have to read 100MB of text to find the info
In my case because the ac power is too far away it makes sense to transform it down to DC, store it in batteries , ship it across 25 metres & rebuild the ac.
I'm happy to wear the inefficiencies if it means I get the confidence I survive a grid failure.
Gary - hopefully I can minimise the voltage drop by using thicker wire.
Steve - you sound like an electrically savvy person
So with a single 75ah battery - if I lose power and the pump draws 100w
ac - the DC load is actually 9.8ah? So it will go for maybe 5 hours (don't want to kill the battery)?
So I parallel up 2 batteries and get 10 hours off power?

Cheers
Jamie

VB, did you get a little leaflet in with the battery with a discharge curve? if so can you post it here to help Jamie with his calcs?

Muz, i'm used to the small SLA batteries AH rate being quoted at the 20 hour rate, are the deep cycle batteries the same?


Jamie, wait for responses to the above questions

but yes, parallel 2 batteries for double the capacity.

Na

Gary - did some research and yes - there are inefficiencies in running low voltage cable.
Here's a calculator: http://www.stealth316.com/2-wire-resistance.htm

From that for 25M at 10 amps I need 6 swg wire for a .33v drop.
Its almost 5mm diameter - Sounds pretty thick.
(I'm assuming a .33volt drop is not significant. power wasted = 0.33 * 10amps = 3.3 watts or 29kw/year. At 20cent a Kw I am wasting $6 a year)

Steve - am I talking sense?

Cheers
Jamie

Jamie, in the end you are better off to avoid long runs in DC especially 12 volts. It just gets too hard to manage. Have your battery charger etc close to the tank somewhere. VB has a good setup to keep the fish aerated in the case of power outage.

Muzza