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Automatic Battery Backup for Linear Piston Pump / Fishroom / Central Air


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I run air to all of my tanks with the same pump sold by the co-op. 

The beauty of this pump is how it utilizes the sinewave in its design. It runs silent and low wattage for its output. But it does present a challenge when running it on backup battery power.

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A silicone diode between the coils converts the alternating current sine wave into a half-wave rectified input. The result is a pulsating electro-magnetic field energizing the resonant spring-mass (piston). When the electro-magnet is energized,the intake stroke of the piston compresses the return spring and draws air into the cylinder through the inlet valve in the head of the piston. When the electro-magnet is de-energized,the spring releases and the compression stroke of the piston forces the compressed air out of the cylinder through the reed style outlet valve.

 

The linear piston pump needs a pure sinewave to operate correctly. It will not work if the supplied power is square or modified sine. For generator use it must be an inverter type model with clean power. Essentially this pump has the same requirements for clean power as a computer or other sensitive electronics.

 

For my pump I wanted to be able to supply backup power air to my tanks without having to break out my inverter generator and extension cord. I also wanted the system to be automatic so it would work overnight or even if I am not home.

 

What I came up with was this

PXL_20210819_183758380.jpg

I bought a 300w "pure sinewave" inverter off of amazon and a 12v deep cycle marine battery from walmart.

I already had the intellipower converter/battery charger on hand. a cheaper, battery maintainer/tender type can be used.

With my design the relays coil will be energized as long as there is wall power, closing both normally open poles of the relay and letting wall power through to the linear pump. During a power outage the coil will not be energized and the relay will switch back to its normally closed contacts letting inverter power through to the pump.

I brought the battery home today and setup what I had on hand to test the inverter/system. Perfect timing, as I actually lost power and the pump ran fine on inverted battery power for about 2 hours.

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This system could be used without an automatic transfer switch/relay by simply running through the converter/charger, then the battery, then the inverter. But you would be losing in efficiency and would be using the inverter 24/7

 

The relay comes in tomorrow with a few other accessories. I will update this once I get it running. 

Edited by StevesFishTanks
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This is a great project @s1_! I don’t have enough tanks to justify the linear pump so I’ve got lithium ion battery pumps that hold a charge - about 6 hours or so is what I’ve gotten from them when Ive tested. But eventually I’ll have enough to justify that sweet sweet linear pump and now I’ve got a battery backup plan to follow! Woot! 

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I have the system up and running now on my linear piston pump. I have the inverter switched to "ON" with no load since I am running on wall power. I am hoping that it doesn't have some sort of sleep or standby mode where it powers down after so many hours of no use. Will simulate a power outage after its been on for a few days to test it.

https://docs.google.com/spreadsheets/d/1-1qJgbKA2RREhzpqpFXHBBIGeVrWuAUQoPQnC0bnb-I/edit?usp=sharing

posted a link to the parts used. I will try to make it easier to understand.  

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This is absolutely an incredible DIY project!  I recently got a LPAP from ACOOP installed.  It's great, but I'm already thinking about a battery backup.  This thread makes me want to consider it more.

I didn't really know how the pump worked, so that was informative as well.  Thanks for posting this!

I am far less confident in my electrical DIY abilities than you are.  Far less!  So, I am curious, did you have to build this, i.e. will off the shelf UPS units for computers not work well?  I am sure this is less expensive, but just curious if there are off the shelf options.  Again, this looks awesome, I'm just a coward when it comes to electrical.  😲

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On 8/22/2021 at 2:59 PM, OnlyGenusCaps said:

This is absolutely an incredible DIY project!  I recently got a LPAP from ACOOP installed.  It's great, but I'm already thinking about a battery backup.  This thread makes me want to consider it more.

I didn't really know how the pump worked, so that was informative as well.  Thanks for posting this!

I am far less confident in my electrical DIY abilities than you are.  Far less!  So, I am curious, did you have to build this, i.e. will off the shelf UPS units for computers not work well?  I am sure this is less expensive, but just curious if there are off the shelf options.  Again, this looks awesome, I'm just a coward when it comes to electrical.  😲

Problem with computer backups is usually very small battery and/or not pure sine wave output. The computers power supply is capable of filtering this while the minimalistic design of the linear piston can not.

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On 8/22/2021 at 2:06 PM, s1_ said:

Problem with computer backups is usually very small battery and/or not pure sine wave output. The computers power supply is capable of filtering this while the minimalistic design of the linear piston can not.

I suspected there would be a snag.  Thanks!  Well, I was following this anyhow, but now with increased interest.  🙂 

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ordered the victron inverter. 

rated to "idle" in eco mode consuming only 1 watt. Makes me feel a lot better since it will be doing nothing while wall power is working, which is most of the time.

It will replace the bestek in the build.  The relay and everything else will remain unchanged. 

Only future improvement is going to a different battery. Lithium iron phosphate most likely. It would increase runtime dramatically but also cost. 

Will update once the victron is installed.

 

PS. just for fun I ran my fx6 and fx4 on the current setup and it worked fine.

Edited by s1_
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On 8/24/2021 at 4:27 PM, DSH OUTDOORS said:

So you are saying my current no knowledge back up isn't going to work?  😂

 

https://www.amazon.com/gp/product/B073Q48YGF/ref=ppx_yo_dt_b_asin_title_o09_s03?ie=UTF8&psc=1

The best way to test it is to simulate a power outage by unplugging it under load.

See what it can and can not run, and for how long.

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  • 1 year later...

Worked great through several intermittent power outages during hurricane Ian.  I am in the Tampa Bay area, we were spared from the direct hit.  Very similar to hurricane Irma a few years ago.

 

I am currently in the process of moving my fishroom and am playing with the idea of adding solar to this system.  I already have all of the components from a solar project that powered a small refrigerator on my old work truck. (2 100w panels, 20a mppt controler, and a lifepo4 battery)

 

edit: When I originally made this post the experiments, community resources, and other categories did not exist. If it could be moved to a more fitting category by a moderator that would be great.

 

 

Edited by StevesFishTanks
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