Trying to set up a solar charged, battery operated pump

[cordex]

Thought I'd revisit this.

For a number of months I've had a LiFePO4 power bank hooked up to a solar panel.  The power bank has a built-in inverter and was running a knock-off of the Hi Blow linear air pump into two air lines then into bubbler stones.  The problem was that if the power bank depleted fully, once recharged it wouldn't kick the AC outlet back on to drive the pump.  Fully charged it would run a few hours, and with solar assist it could run all day during daytime, but would cut off most nights and not start up again in the morning.  I tried putting an AC timer on it, and could get it to run a couple hours during the day, but if we had several cloudy days in a row it would eventually run down and wouldn't start back up.  Also, the AC timer and the power bank's fans would slowly deplete the battery on their own.

Back to the drawing board.

When I took down my solar-powered maple sugaring vacuum pump I decided to reuse some of the solar components for the pond pump.  The solar panel is a generic 110W panel and feeds into a Renogy Wanderer.  The Wanderer charges two parallel LiFePo4 batteries with a total capacity of about 40Ah which drive a 110v inverter.  I previously had the inverter wired into a low power 12v loop timer I had used on the maple sap system, but the relay terminals are just too small to get a solid connection and this was causing problems.  The system runs itself completely dead sometime during the night, and at about 11am is getting enough power from the panels to start the pump and start charging the batteries.  Because it's a dumb system it doesn't need to be turned back on when it gets power - if it has enough juice to run the pump it does, if not the BMS in the batteries shuts it off.

This type of abuse wouldn't work well with lead acid batteries, but the LiFePo4 ones seem to be working okay.  I'd like to either get a low voltage cutoff or put a new relay in for the timer.  I think the new relay would probably be the best idea.  That way I could have the pump cycle on every few minutes.  Reducing the duty cycle by half would mean that the batteries should typically be able to carry on regular operation through the night and get recharged during the day.  A long cloudy stretch might still cause it to die eventually, but it would come back online with enough sunlight.

The battery, pump, and charging hardware are all in a black plastic tote with holes drilled for drainage, to run the cables to the solar panels, and for the pump hose.  I'll have to keep an eye on the heat levels in the summer.  The solar panel rests against the tote facing south.  When I'm confident in the system I think I'm going to move it to the north side of the pond so it is less visible from the road.

[Ben]

Good timing bringing this up. I think I'm gonna copy some of what you're doing. Looking back at the thread, I see that one of my recommendations for a small pond was those Amazon chicom kits. I would no longer recommend them. I had two of them fail since the start of this thread.

I'm now going to use a small Hiblow 20, Harbor Freight panel, and a spare battery that I've had sitting in the shop to do the same setup I have on my big pond except smaller scale on solar. I'm taking notes on your setup. 

On having your aerator in a box in the heat, you can always cut airholes in it. What I did for my grid power Hiblow is build a wooden box with the top having a 4" overhang on all sides. Then I cut 2"slots at the top of the sides and stapled window screen material over the holes, so it works sort of like attic vents on a house, and the "overhang" keeps rain from getting in the box.

That seems to keep it from overheating, though these Hiblow style septic pumps seem to be pretty robust for the environment they can take. I also have the big pond aerator on a timer so that it's off from around 2PM-7PM in the Summer. From reading, it's not necessarily good to blow hot air into a pond where the water might also be heating up from the Summer sun.

[cordex]

I had two of the little solar chicom pumps fail too, but they were way undersized for my pond anyway.

That seems to keep it from overheating, though these Hiblow style septic pumps seem to be pretty robust for the environment they can take. I also have the big pond aerator on a timer so that it's off from around 2PM-7PM in the Summer. From reading, it's not necessarily good to blow hot air into a pond where the water might also be heating up from the Summer sun.

Good info, thanks!

I could put vent holes under the edge of the tote pretty easily.  Not as good as your option as the overhang is much smaller, but a step drill and 5 minutes and I can have that taken care of.  Plus, any rain that does get in shouldn't impact things much given how I have things positioned and the drain holes I already have will let the water out.

[cordex]

So one problem that I should have foreseen was that the AC timer I'm using isn't keeping good time.  It relies on AC frequency for timing and the cheap inverter I'm using isn't outputting pure sine wave.

I'm going to have to get something else to serve that purpose.