Design Check

[bigredball90]

Building a small system to run a small water pump and possibly other small loads in the future. Pump has a 10w draw at 18v.
Looking at a Victron MPPT 75/10 12/24v SCC, with 2 100w panels, and battery hookups new Lifepo4 battery. Looks like it would be easy to series it later if I decide I want more power. Plan is to run it as 12v for now and use the drok converter to get 18v. It doesnt appear that the battery has a low temp cutoff so I might have to add a Victron smart battery sense later on to keep it from freezing as the battery will be outside year around. I also will need to find a water tight box to fit everything in, not sure if it will overheat during the summer though.

Any thoughts or critiques are welcomed. Thanks for looking.

Parts list:
Amazon.com: ECO-WORTHY 2pcs 100 Watt Solar Panels 12 Volt Monocrystalline Solar Panel for RV Marine Boat and Other Off-Grid Applications, 2-Pack 100W… : Patio, Lawn & Garden
Amazon.com: Victron Energy SmartSolar MPPT 75V 10 amp 12/24-Volt Solar Charge Controller (Bluetooth) : Patio, Lawn & Garden
Amazon.com: DROK DC Buck Converter, 5.3V-32V to 1.2V-32V 12A Adjustable Power Supply, 5v 9v 12v 24V 30V 32V Step Down Voltage Regulator with LCD Display Volt Transformer Reducer CC CV for RV Solar Panel Golf Cart : Electronics
Amazon.com: M1A2 Circuit Breaker Switch 15A Waterproof Fuse Inline Holder Resettable Fuse Manual Reset 12V-48V DC for Car Audio Sound Amplifier System RV Home Marine Boat Truck : Automotive
New 12.8v 30ah Lifepo4 Battery - Series 12/24/36/48v – Battery Hookup

 

[MisterSandals]

Pump has a 10w draw at 18v.

10W / 18V = .55A call me skeptical. How did you arrive at the 10W number?

2x 100W solar / 14V charging = 14A A 10A charger can leave 4A from the panels unharvested. 15-20A charger better.

 

[bigredball90]

10W / 18V = .55A call me skeptical. How did you arrive at the 10W number?

2x 100W solar / 14V charging = 14A A 10A charger can leave 4A from the panels unharvested. 15-20A charger better.

It's the rated watts from the manual. It's a small solar powered pump that my wife now wants to run 24/7. I don't have an amp meter yet to double check the actual current.

Yea that's a good bit I would be missing, guess I need to decide if it's worth the few extra $$.

 

[MrThisIsME]

Pretty sure motor and 10w should never be used in the same sentence.
Are you sure of this spec?
In regards to leaving the battery outside, you would have to disclose your location. Key West or Anchorage would make a huge difference in that regard.

 

[bigredball90]

Pretty sure motor and 10w should never be used in the same sentence.
Are you sure of this spec?
In regards to leaving the battery outside, you would have to disclose your location. Key West or Anchorage would make a huge difference in that regard.

Location is upstate SC. We do get below freezing, usually just at night though.
The tech data on the pump:
Operating voltage: 18v
Included solar panel power: 25w
Max pump power: 10w
Max water lift: 6.9ft
Max flow rate: 370gph

Amazon.com: 25W Solar Water Pump KIT: DC Dry-Run Protection Water Pump 370GpH with 18V 25W Solar Panel for Fountain, Fish Pond, and Aquarium (No Backup Battery) : Pet Supplies

 

[MrThisIsME]

Location is upstate SC. We do get below freezing, usually just at night though.
The tech data on the pump:
Operating voltage: 18v
Included solar panel power: 25w
Max pump power: 10w
Max water lift: 6.9ft
Max flow rate: 370gph

Amazon.com: 25W Solar Water Pump KIT: DC Dry-Run Protection Water Pump 370GpH with 18V 25W Solar Panel for Fountain, Fish Pond, and Aquarium (No Backup Battery) : Pet Supplies

Got it. Correct to assume bird bath or pond pump?
Have you actually tested the pump before hand? Something about specs and Amazon / Chinese never seem to line up.

I have done similar for wifi APs and wifi camera. Took an irrigation box buried it in the ground clean gravel at the bottom , then put in a NOCO group 31 battery case. Inside the case, battery, cheap but decent MPPT controller (with no display) and a boost convertor. For SC I would not worry about freezing if buried as such.

Unless you have a compelling reason for the Victron MPPT, save your money.

No need to run a circuit breaker unless you want a disconnect. In the rare times you want to disconnect, an inline 3A fuse would be less complicated. Remember the fuse / breaker is only to protect the wire you run.

For your buck convertor, find one you can put in large heat shrink. I usually use three pieces on large shrink for the unit and two pieces on each side to reduce the larger one.

30aH battery should be OK. Might get caught on a couple of cloudy days (quick math). Problem is there seems to be a price gap to go from 30aH to 50aH. At the price you listed, I would be inclined to try the 30ah, if not add a second in parallel (not series as you mentioned).

Check your math, 200w of PV might even be overkill. Nice in the Winter though.

Just keep it simple and all connections encased, best you can.

 

[hwy17]

Don't put 12v batteries in series if you can avoid it. They can't stay balanced.

Edit: Oh that's panels in series. Nevermind.

 

[bigredball90]

Got it. Correct to assume bird bath or pond pump?
Have you actually tested the pump before hand? Something about specs and Amazon / Chinese never seem to line up.

I have done similar for wifi APs and wifi camera. Took an irrigation box buried it in the ground clean gravel at the bottom , then put in a NOCO group 31 battery case. Inside the case, battery, cheap but decent MPPT controller (with no display) and a boost convertor. For SC I would not worry about freezing if buried as such.

Unless you have a compelling reason for the Victron MPPT, save your money.

No need to run a circuit breaker unless you want a disconnect. In the rare times you want to disconnect, an inline 3A fuse would be less complicated. Remember the fuse / breaker is only to protect the wire you run.

For your buck convertor, find one you can put in large heat shrink. I usually use three pieces on large shrink for the unit and two pieces on each side to reduce the larger one.

30aH battery should be OK. Might get caught on a couple of cloudy days (quick math). Problem is there seems to be a price gap to go from 30aH to 50aH. At the price you listed, I would be inclined to try the 30ah, if not add a second in parallel (not series as you mentioned).

Check your math, 200w of PV might even be overkill. Nice in the Winter though.

Just keep it simple and all connections encased, best you can.

Yes small 300 gallon pond. I have not tested it, I do not have a way to measure amps yet.

Yea I was considering putting it underground, still need to mount the mppt, and other stuff inside a water proof box somewhere though. Its in the lower part of my yard where most of the water runs to.

The one Im looking at is under $70 havent really seen anything (good quality) cheaper on amazon. I was also considering this one so I could add the victron battery sense if needed later as well. Are the cheaper amazon ones worth it?

Not a big deal if it misses a day here or there, its just some pond plants and guppies.

Yea 200w might be to much but its only $40 more for the second panel over the $70 single, and would be nice if I decide to add a second battery and more stuff later.

Thanks for the help!

 

[MrThisIsME]

Ponds right up my alley. I would defiantly test the pump first, see if meets expectations. Even on the cheap pumps, the flow advertised is always rated at zero or 1 foot of head. To be honest, 10w is not going to move a lot of water. If it is just a visual effect and moving some stale water a pond aerator would give you more effect for the wattage and better for the fish. But do the test first on the current pump. Look of work and planning without the desired effect at the end.

If you are content on the Victron for that price, go with it. I run some $20 cheapies off Amazon with no issue. Not real critical for my application but they never failed.

In my above mentioned usage, I use AGM batteries. Do not have to worry about them here in Maine, buried in the ground. Not the best way to treat them...............but .......... I had a bunch come to me for free, so the cold benefit of AGM plus the cost was the reasoning.

If you really wanted to get fancy and the setup is near wifi, a Shelly relay would work. Could turn off at night to save power if you wanted. The ones on Amazon are expensive, shop around for a $10 one. If you decide such, just make sure you get one that runs on 12vDC, most do not. The power monitoring might seem attractive, but they are only for AC.

https://www.amazon.com/Shelly-Wireless-Automation-Android-Application/dp/B07NQNLDTD/ref=sr_1_7?crid=XY3FK4CKIWKX&dib=eyJ2IjoiMSJ9.ctb0PNNpMn0nlJ68B_zapvrHy0JdWFIg8uPKxaphZ0tiNrHObU4VWGWtPc7Y508NABggsv_sg8liR-sm01xJ_1O0dy6bYH__vXUxc8u-Sfu7mbs8AdBpAfjOK2-4S_SHg4RFynYQPAt2kZ15UA1_iY4qf7qwrr-tj90JaBkRgR_tLeO3V9dpcksWkO0JeTmN_xEzjjSVhzOXRv5AVBCTvHiTDoah2t9xBdv_GUnHjUyXErqsTjsUKExJ-uAxHm7hgBcTDS6sWj0h4jObA6wolW8GiwFbTXbXUWzJBy0mAOM.Idjpko6B_2re4WaZP7LGSt3DUBEmPahmGOVSpDNjJ_s&dib_tag=se&keywords=shelly+1&qid=1711668309&sprefix=shelly+%2Caps%2C168&sr=8-7

 

[bigredball90]

Got my amp meter in today. Results are 21.25v from panel, and a 0.3a draw from the pump. 6.375w surprisingly less than rated. I tilted the panel to make sure it was pointed right at the sun when pulling the info as well.

Yea its not the best but better than nothing. We have it routed up into an old style hand operated well pump so it water falls back into the pond.

I have not heard of a shelly relay but that might be usefull if I want to add a wifi camera out there at some point. We get deer from time to time and they would be fun to watch. That and see what kind of activity my new bee hives have

Decided to just get the 75/15 victron, could be useful in the future if I want to add more power or use it for another project at another point.

 

[robbob2112]

Got my amp meter in today. Results are 21.25v from panel, and a 0.3a draw from the pump. 6.375w surprisingly less than rated. I tilted the panel to make sure it was pointed right at the sun when pulling the info as well.

Yea its not the best but better than nothing. We have it routed up into an old style hand operated well pump so it water falls back into the pond.

I have not heard of a shelly relay but that might be usefull if I want to add a wifi camera out there at some point. We get deer from time to time and they would be fun to watch. That and see what kind of activity my new bee hives have

Decided to just get the 75/15 victron, could be useful in the future if I want to add more power or use it for another project at another point.

Not surprising it is less. Less copper in the motor, less push pressure, less head, less current.