UPS battery air pump

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Richies^Ghost

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MFK Member
May 15, 2010
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So instead of twiddling my thumbs or doing my uni work whilst I'm waiting for bulkheads to arrive in the mail, I'm making an uninterrupted power supply for my 10watt air pump.

This consists of a 12v 75ah deep cycle battery on a trickle charger, hooked up to a 300w inverter, hooked up to the pump. The power goes off, the pump continues to run until the battery dies 70 something hours later.

What I'm having trouble with is taking it a step further, so that the mains and the inverter run through a relay to the pump. This is so that the pump normally runs off the mains (via an extension cord) but when the power goes off, the inverter starts and the pump runs off the battery.

My questions are:

1/ Will this work?
2/ What else is needed (i.e. fuse, regulator, etc.)?
3/ How can I set it all up?

Please keep in mind that I have little to no idea what im doing here, and would rather not end up on the floor :ROFL:

Thanks! :)
 
I'm not an expert and i have seen plans for this on other sites.

You are right you need a relay double pole. While the relay recieve AC power it will be switched one way and will send power to the pump. When the power goes off the switch will flip back to it's resting state and power the pump from the inverter. Then when the power comes back on it will switch back to your AC power.

Not a very hard project to do once you under stand relays a bit. Hard part is making is compact, clean looking, and safe from water.

Less fun but might be easier to buy a computer UPS never really looked up pricing though. I'm sure you can build one with a better batery for cheaper.
 
I would use a computer UPS and ONLY a computer UPS. Car batteries, as you want to use, release Hydrogen under charging. Hydrogen is extremely explosive... this is why you have vents in car battery compartments or the battery is located under the hood of a car. ("In 1952, the 10.4-megaton 'Ivy Mike' explosion was announced as the first hydrogen bomb test, reinforcing the idea that hydrogen bombs are a thousand times more powerful than fission bombs.") = Be F***ing careful. Please.

The only way to avoid this, and mind you its still not a fully safe way, is to use a sealed Gel Cell marine battery. Even better, if you insist on this, is to make sure you vent the gas to the house exterior.

<<<btw, I'm an aircraft electronics engineer.
 
Very good point becareful, as with all DIY. Most new batteries are sealed and do not realses hydrogen.

Also there is a bit if a diffence with exploding hydrogen and an atomic bomb explosion from spliting hydrogen atoms....
 
You will probabaly be better off with a computer UPS.
If you try your original idea you will need more than a relay you will need an ATS,"Automatic Transfer Switch" ,which by itself will cost you more than a decent UPS.
It could be done but it would be cost prohibitive.
Just as a note, many larger 750Ah + Ups units use sealed wet cell batteries.
 
original idea you will need more than a relay you will need an ATS,"Automatic Transfer Switch" ,which by itself will cost you more than a decent UPS.

No, really. a single relay can switch the load between line voltage and the batt/inverter.

you need a relay double pole. While the relay recieve AC power it will be switched one way and will send power to the pump. When the power goes off the switch will flip back to it's resting state and power the pump from the inverter. Then when the power comes back on it will switch back to your AC power.

Just as the above states.
 
So this is the relay I've gotten:

ShowLargephoto.asp


http://www1.jaycar.com.au/productView.asp?ID=SY4044&keywords=relay&form=KEYWORD

Though I don't actually know how to hook it up! It was explained to me in store, but I didn't write it down. Any ideas for which wires go where? Trial and error doesn't seem the right way to go here ;)
 
Also, the website lists the power consumption as 4W - does this mean it's constantly going to be drawing 4 watts, or is this for when it flips over?
 
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