Backyard Aquaponics
A place to discuss aquaponics

In the 2nd hand cabinet I bought it has a 24v UPS built in with 2x12v batteries. I was wondering if I should power my air/water pumps off this or only use the 24v circuit for powering the logic and then include separate heavier 12v car batteries with inverters to power a backup 240v AC pump circuit.

Any thoughts?

Nitrate Probe please!

I'll give you one of many many examples. To add an ambient temperature and humidity sensor to the Reef Keeper, you would have to buy the AP1 module which costs $75. If I want to add a temp/humidity sensor to the Arduino, I need a DHT22 module which costs about $4.


That too



What is the AH rating of the 12V batteries? Does it have an inverter built in? How many watts does your pump draw? Base on this info, we can determine the backup duration and if the 24V backup will be adequate.


Never found one that is affordable. Cheapest I found is about $300 but you can't leave it in the tank and you have to replace the membrane every 30 tests. I'm still hoping Atlas Scientific releases a Nitrate kit as was rumored.

I didn't lift the batteries covers but I'd say they are fairly standard and around 7ah. The power supply is rated at 2.5A but it feeds the UPS controller which is rated at 20A. And I mis-printed my earlier message, it actually has 4 x 12V batteries running at 24v.

Thanks Chiumanfu, I'm starting to think I should use 240v gear but perhaps have some smaller air/water pumps that can run 24v on backup?

How many watts does the pump draw? A bank of 4 12V 7AH batteries will give you 14AH at 24V. If your typical pump draws about 150W, the batteries will only last 6.25 hours in an ideal world. In the real world, the time will be much less. First, the inverter is not operating near max capacity so efficiency could be as low as 50%. Second, a quality inverter won't let you run the batteries all the way down, it depends what the low voltage cutoff is set to. Third, the load is drawing faster than the 20 hour span that the AH rating is usually based on, thus the actual AH rating will be less.

My best guess is that you'll get less than 4 hours of backup time with a 150W load and 7AH batteries. Not much good if you ask me.

I'm also going to guess that the power supply is just for charging the batteries so it's amp rating doesn't matter.

Good reply Chiumanfu. To date power outs are usually not longer than 30mins at most, once I did experience one that was 3 hours though. When I've lost fish (several times now) its because I did something stupid and I had no alarm in place. So simply adding the alarm should eleminate my biggest risks.

I found this pump which looks adequate, http://www.ebay.com.au/itm/181564114033 rated at 85W with variable speed, I'd need to lift around 2m and I could probably still reduce its speed by 25% to save a few watts.

Additionally when in power-failure mode I could perhaps cycle the pump, on for 30mins off for 60mins, and during the 60mins off time I could run a 35W 24v air pump and even cycle that, 5m on 5m off. http://www.ebay.com.au/itm/121643243398

But.. having said that, and digesting what you said, its probably wisest to separate these functions. Allocate the 24v UPS for the Arduino, monitoring, logging & control and build a separate heavy-duty 12v battery system with 240v converter. I could still use the cycle concept to conserve power and maintain better logs of what happens during a power out probably.

If I went with the 240v converter route, is there a way I can switch power sources in a power out in order to use my existing pumps with full on/off control still?

Thanks again, bouncing ideas off you is really helpful.

If you always run the system from the batteries, and leave the batteries on a smart charger, you don't need to switch from 240v mains to 240v battery supply.

The batteries are kept full so they will last for years and years, and you don't need to play with 240v switching, so there's less getting killed

That's always a bonus of course. Seems like a good suggestion, it means your always running through a DA / AC converter though which probably means a big loss of power, so higher electricity bill. In a power out I would only care about air pumps and water pumps, in that order. But there are many other things I would probably run when on the normal power grid, Fans and/or Hothouse roller motors, valves, cameras, etc? So you'd never really want these items running via battery of course but no reason to not run the pumps in the way you suggest perhaps.

Is this what other people are doing?

ps. your chickens finally died of old age and the emu ran away, can you supply more please

Your power supply (charger) is only 2.5A so at 24VDC you'll only get 60W. If you pump draws 80W and you run off batteries continuously, you'll never charge the battery.

Here is the circuit for my backup scheme. I'll try to walk you through it.


If you don't care about backing up the arduino, you can ignore the whole middle section. You can also ignore the Relay Module at the top right. This is for controlling the sump pump based on the sump level float so the pump can't run dry.

When the mains power is present, the 5VDC adapter at the bottom left powers the coils of relays RY3 and RY4. RY3 disconnects the input to the inverter and RY4 connects the Hot side AC to the pumps. Pumps are running from mains power and everyone is happy.

When the mains power fails, the 5VDC adapter is off and the relays RY3 and RY4 switch to their normally closed position (shown in schematic). The inverter input is connected to the battery and RY4 connects the AC output of the inverter to you pumps. AC mains Hot side is disconnected and your pumps are now running off the inverter.

The relays are standard 5VDC SPDT and the 5VDC Adapter is simply a cell phone charger. I'm keeping my battery topped up with a small 10W solar panel and simple solar charge controller and everything is working perfectly.

It has also come to my attention that RY4 should really be a DPDT relay and switch both HOT and Neutral leads at the same time. This is because some inverters use a "hot neutral". Mine doesn't and it works fine so I haven't changed it yet. Always properly ground everything and if it doesn't make perfect sense, seek the help of an electrician.

I have no idea of the fate of the pets when we left the farm. I'm confident they went to good homes, but I couldn't bare to see them again, then lose them again. It would be different if we could see them every weekend or something, but it's heart wrenching to lose pets you thought would be lifelong friends.

I want to get 2 chickens for my epic Murray river adventure, but I'm not sure if I should

When I ran my system on the farm, we often had power outages that lasted for a few hours so I ran a backup system as described. I'm in suburbia now so we don't have the problems we used to, so I dont bother any more.

I think the losses would be around 10% from mains to charging the battery, then 10% from 12v to 240v, but I think you will always see this in a battery backup inverter system...

I think

I have herd about this and someone another place had mentioned about mains voltage grounding also. If you ground wire everything together or if that is changed by the relay? So it grounds to the inverter instead of the house ground when the system trips.

I'm only on page 7 but I joined just to day this idea is exactly what I've been combing the web looking for. I have a RPi B & no Arduino. I would also like to interface with a keyboard & monitor.

I'm not a programmer but send that if you ran the Arduino off the batteries ask the time seeing how it should use almost not power you could add a wall wart to a pin & as a line of code to read this pin as high then do nothing but if it is low to trip the relays to run your backups & everything should run as usual without running the relay all the time using more power & heating the relays & causing them to fail sooner. A 1 mA wall wart should be able to do this right?

I'm having a hard time understanding the question but I'll try to answer. The Arduino mega by itself can draw approx 200mA if it's running hard so it's not feasible to run of batteries unless you have a solar setup and a large battery. You can definitely sense the AC power line status with a 5VDC wall wart plugging into a digital input but you will need a pull down resistor to ensure that the pin doesn't float when the power fails. If your wall wart can only deliver 1mA then the pull down would need to be 5kohm or greater. That doesn't make for a very solid pull down. A more typical scenario would be a 1kohm pull down resistor and a wall wart capable of at least 5mA.

I hope that answers your question.

The AC grounds are all tied together. I see no reason to switch the AC grounds through a relay. It actually defeats the purpose of the AC ground.