taking the pool pump solar powered

[Hedges]

For single-phase motors with capacitor start/run, not for those with centrifugal switch.
1200 to 2900 RPM. That is a larger range and I've seen quoted for some. Of course many motors will run on either 50 or 60 Hz.

https://heatpumps4pools.com/myfiles/file/iSAVER-Frequency-Inverter-user-manual.pdf

Mine was 3600 RPM (60 Hz over here), and I reduce the speed but not as low as 1800 or it doesn't move enough water.
Great if it works for single-phase motors. 3-phase would be best. I got a deal on a new one from eBay, so it was cheap. I see some listings currently but not cheap these days.

 

[Warpspeed]

Got a DC pool pump motor?

You're right it would be simple. And some brushless DC do that. I run fans that way, off a couple solar panels.

If the $200 photovoltaic VFD is good, that's reasonably economical. But 3-phase pool pump motors don't come cheap.

The existing ac pool pump motor will have a shrouded fan at the back to blow cooling air across the motor fins.
Remove the fan and fit a toothed pulley.
Connect that through a belt to the dc motor of your choice.
Use reasonably large diameter pulleys, and with a toothed belt, it does not need to be stretched super tight to prevent slippage.
That will keep the drive system as efficient as possible.

Now the ac pool pump motor, new dc motor, and the solar panels all have rating plates attached, from which you can get enough information to make a pretty good attempt at establishing a suitable pulley ratio and number of solar panels required.
An internet search may uncover even more details from which to engineer your system.

What happens is if the dc motor were completely stalled, the solar panels will be putting out max available short circuit current, or something pretty close to it.
The motor will be generating its maximum stalled torque at zero rpm at full rating plate amps.
The pump impeller requires almost no effort to initially start turning.

The motor rapidly accelerates up to the point where the impeller consumes all of the available motor torque. The solar panel voltage rises too as motor speed increases.

If you judge it just right, you can tweak the pulley ratio and number of solar panels so max pump power coincides with max peak power developed at the solar panels. Its so simple, and the most efficient system possible. Even on cloudy days it will shift enough water to be quite effective.

There is a thread about someone doing exactly this with a secondhand treadmill motor, with lots of pictures and information over on The Back Shed Forum.

If you plan to use the original pump motor grid connected, and run it for extended periods, it should be possible to rig up an external grid powered cooling blower to replace the fan removed from the motor shaft. Those original crude little plastic fans are pretty crappy, and the ac pump motor may not really need any extra cooling anyway.

 

[NO_SafeSpace_4U]

Buy one of the kits that come with solar-ready DC motor panels battery and a charge controller. Probably wind up saving money

 

[rogerdw]

Interesting to come across this thread as I don't spend that much time in this forum.

As Warpspeed has described above is exactly what I've done to take our pool filter pump off grid and save us considerable dollars ... in fact he was instrumental in encouraging me to try out the idea in the first place and provided a lot of advice in the process.

It's been running daily for two and a half years now and is on its 3rd belt, so very happy with the results. It can't get much simpler than some panels, a dc motor and a belt ... no electronics or any other form of control ... just wait for the sun to come up and it does its thing.

If anyone is interested and wants to see photos and the setup, the whole exercise has been described over on thebackshed forum ... https://www.thebackshed.com/forum/ViewTopic.php?FID=10&TID=13406

 

[Warpspeed]

Great to hear from you again Roger !
I was wondering about how the whole project finally turned out.
Sometimes the simplest solutions are the best.

 

[rogerdw]

Thanks Tony, and thanks for your help putting it all together in the first place. It's been amazing being able to forget all about it and have it work day after day with virtually no attention.

Working from home, I walk past the pool area often and occasionally wander over to the fence to peer at the pressure gauge just to make sure it's still doing its job ... though the sound pretty much is all I need to hear to be confident it's still pumping away.

The first belt lasted exactly one year and the next one the same before they became shredded and started falling off. The third one had to be adjusted 3 or 4 times before it settled in and I haven't adjusted it in probably 6 months since. If you hear it start to squeal a little you know it's time to nip it up.

While the pump is an Onga and seems good quality, the base is plastic and I had to modify it a little as the plastic had pulled out of shape ... and the belt wasn't running quite true when I fitted the new one at Christmas time. I think this belt will last a lot longer because it has remained aligned properly.

It always used to fascinate me when I would hear it winding down late in the day and occasionally would hear it come to a stop ... and other times when it was overcast and you wouldn't expect much solar output ... yet it was whirring along quite strongly.

And for those who kept saying that the motor was going to burn out when it stalled ... well it hasn't yet. ?

 

[Warpspeed]

It sounds like the belt works fine, until it starts to slip a bit, then its down hill from there.

Either much larger diameter pulleys of the same type (and ratio), or better still toothed timing belt pulleys should completely solve the problem.
One belt a year is not too bad, and a rebuild probably not worth the effort.

But for anyone else thinking of trying this idea, belt slip with the original very small treadmill pulley will likely be a long term issue.

The motor pulley just screws onto the motor shaft, and the easiest way to get it off is to flash the motor with full rated dc voltage in the reverse direction.
The very heavy treadmill flywheel offers enough inertial resistance to unscrew the pulley.

The physically larger treadmill motors are rated 2Hp to 3Hp and that is what you need.
Check out e-bay they usually go secondhand for under a hundred bux.

 

[rogerdw]

Yeah once the belt starts to sqeal, it needs attention. I only nip it up enough to stop the squeal so it doesn't apply too much tension on the bearings and friction from the belt ...

... so some bigger pulleys would certainly help ... but I think the ultimate would be toothed rubber belts ... so then it wouldn't need anywhere as much tension to prevent slipping.

When I had trouble early on, I bought some non-slip belt spray ... and the occasional application of that certainly stops slippage for a while ... but ultimately it needs adjustment to settle it down for months at a time.

Treadmill motors are fairly abundant and even complete treadmills are often offered for free on facebook marketplace just for picking up. Though there's only so much you can do with all the frames and rubber mats etc.

I also had a cousin turn up a couple months ago with two motors, one 2hp and another 3hp ... 180V DC ... and they are serious looking motors ... easily 3 or 4 times the size of my treadmil motor. He had a solar pump business for years and eventually sold it and now that he's retired has no use for them anymore.

 

[Warpspeed]

If you do decide to do anything with toothed belts, I have a lathe here and may be able to help.

 

[rogerdw]

Thanks for the offer Tony but I think I'll leave it alone while it's working okay.

As you know I'm building one of your Warpverters and so once it's finished I may even go back to ac for the pool pump and add the dedicated panels to my full system. I'm pretty slow with my projects as usual but it is coming along. I have the toroidal transformers mostly completed, just need the final primary windings ... and my boards should be here soon too. I got a bit sidetracked working on the board layout for the mppt control so I could order all the boards together.

 

[Warpspeed]

I have several simultaneous projects going on here at the moment, and plan to order boards for all of them at the same time.
The boards themselves are really inexpensive, but postage from China is becoming horrific.

The high power lithium cell balancer is coming along nicely, I know you are particularly interested in that.

There is also a really simple low cost basic analog mppt solar controller that I have been thinking about for a very long time, a battery discharge tester, and finally a circuit board for my Geiger counter that I put together just after Fukushima.

One other interesting project is a circuit to couple together two separate battery banks that have different voltages.
It then becomes a "virtual" parallel connection, charge can transfer from one to the other to keep both at similar charge states.
It uses a buck converter in one direction, and a boost converter in the other direction.
This seamlessly shuffles power between a low voltage battery bank and a higher voltage battery bank.

 

[Hedges]

Hinge and spring to automatically tension?
Spring-loaded tensioner from a car?

One other interesting project is a circuit to couple together two separate battery banks that have different voltages.
It then becomes a "virtual" parallel connection, charge can transfer from one to the other to keep both at similar charge states.
It uses a buck converter in one direction, and a boost converter in the other direction.
This seamlessly shuffles power between a low voltage battery bank and a higher voltage battery bank.

What voltage difference is supported?
This could be good for lead-acid primary battery and lithium extra battery.
Lead-acid could generally be kept at float, and will never suddenly disconnect.
Lithium would provide cycles, and would be limited to current it was willing to supply or accept.
The DC/DC converter should have data bus to talk with BMS of either/both batteries, to support whatever application someone has.

 

[Warpspeed]

Any voltage difference (within reason).
All it does is compare the two battery bank voltages and decide which way to pump power.
There is a dead band, where there is no action if the two battery bank voltages are within a few tens of millivolts per cell.
But as soon as there is a detected significant difference in voltage, it starts to correct.

The reason I am doing this is that I have a 100v system with thirty 50Ah lithium cells. It only stores 5Kwh nominal, which is only one night plus one days storage. If the following day is really cloudy, I am then out of luck trying to get through the following night.

I don't really need the extra capacity of thirty more 280Ah cells, or the extra cost that involves.

But I am going to start with sixteen new 280Ah Chinese lithium batteries and see how that goes.
Later I may decide on purchasing more of these larger cells, and my system can accommodate any number of cells in either battery.

It does not need to be hugely powerful either to be effective. Although it could handle any amount of power, its just sizing of the parts.

For me, its more a case of continuous topping up over 24 hours, taking power from the larger lower voltage battery and keeping the higher voltage battery at a reasonable state of charge, if I get two or three crappy solar days in a row.
I could also charge the lower voltage battery independently with its own solar controller, all the charging power does not have to flow through my circuit. Although it possibly could be made to do that.

If you think about it, shifting only two amps would transfer a full 5Kwh over 24 hours and keep the smaller high voltage battery fully charged !
The smaller battery handles surge loads just fine as it now is, it just does not have the long term staying power.
So a fairly small low cost device should work quite well for what I need it to do.

Its very early days yet. Still playing with the first working prototype.
The actual final control strategy has yet to be determined, but the bi directional power transfer system, which is the heart of it works fine.

No plans to commercialize it, that would be difficult anyway, because everyone's needs would be different.

Its more a case of inspiring others here to perhaps attempt something similar themselves.
Like the solar pump idea, once suggested, it might turn on a light bulb in some peoples heads.