24 volt solar sytem for operating recirculating pump

[Bill M]

I have an Epever 10 AMP mppt charge controller with a single 25-watt solar panel and 12v battery that powers a water-recirculating pump, no inverter. The pump at 12v moves 240 g/h. I am adding a second panel and battery to make it a 24v system and the pump will move 410 g/h.

I'm not well-versed in parallel and series functions. I believe the batteries need to be wired in series to produce the 24v, while the panels should be in parallel to be equivalent to 50 AMP.

Can someone confirm this? If so, is this how a diagram would look? I would appreciate any input from someone knowledgeable in solar electrical systems.

[luna-tuna]

Wiring in the solar panels in a parallel circuit does not double the wattage ( but does double the amps). If you want 50 watts then you should wire up the solar panels in series too. ( I think )

[Txhunter3000]

I helped a neighbor with something similar and you can't get cheaper than the electric grid.

[Bill M]

Wiring in the solar panels in a parallel circuit does not double the wattage ( but does double the amps). If you want 50 watts then you should wire up the solar panels in series too. ( I think )

I guess my main question about all this is how best to wire the solar panels for best charging efficiency. Series or Parallel. After reading a bit more I'm now thinking in series.

.

I helped a neighbor with something similar and you can't get cheaper than the electric grid.

This is for a very small time thing. The pump shown in the diagram above is the pump I'm using. That is what the power is for. See below. Recirculating pump for the waterfall and handpump.

[Txhunter3000]

You have to know how many watts per hour when it runs and how many hours it will run in 24 hours to begin to figure it out. How many amp hours are your batteries? I made a spreadsheet for my neighbor so she could plug in different variables for 2 freezers and it was quite evident she didn't have the storage capacity. You haven't said if you're just running all day and night or just daytime. There are a ton of variables. My neighbor spent $1500 on 600 AH of batteries that won't run them for more than 3 hours a day of full sun.

[Bill M]

You have to know how many watts per hour when it runs and how many hours it will run in 24 hours to begin to figure it out. How many amp hours are your batteries? I made a spreadsheet for my neighbor so she could plug in different variables for 2 freezers and it was quite evident she didn't have the storage capacity. You haven't said if you're just running all day and night or just daytime. There are a ton of variables. My neighbor spent $1500 on 600 AH of batteries that won't run them for more than 3 hours a day of full sun.

Mine is not as complicated as what you figured. I am running the one small pump shown in the OP illustration. I am just needing to know if I run the panels in series or parallel. I have been told in series. Thank.

[Samson]

Mine is not as complicated as what you figured. I am running the one small pump shown in the OP illustration. I am just needing to know if I run the panels in series or parallel. I have been told in series. Thank.

Series is correct. You need to run your panels the same as you run your batteries, which in this case is in series.

[91cavgt]

First thing is first Bill. Go look at the tag on the back of your 25 watt solar panel. More than likely, it will say that the maximum voltage is going to be around 18-20 volts. If that is the case then that is going to be a “12 volt” panel. If the tag says 28-32 volts then that is going to be a “24 volt” panel.

If the panel is a 12 volt panel then the two panels will have to be wired in series to give 25 watts at 24 volts. If the panels are 24 volt panels then you can wire the two panels in parallel and get more amperage.

Wiring the panels in series will be the exact same as wiring the batteries in series. Simple connect a positive from one and the negative from the other together, then use the remaining positive and negative to connect to the charge controller.

Keep in mind that when you wire panels in series, your voltage will go up but the amperage will stay the same. Same goes for the batteries. With the panels when they are wired in series, if just one panel gets a little shade on it then the output of both panels will drop significantly. So make sure they are in a shade free area.

[91cavgt]

You have to know how many watts per hour when it runs and how many hours it will run in 24 hours to begin to figure it out. How many amp hours are your batteries? I made a spreadsheet for my neighbor so she could plug in different variables for 2 freezers and it was quite evident she didn't have the storage capacity. You haven't said if you're just running all day and night or just daytime. There are a ton of variables. My neighbor spent $1500 on 600 AH of batteries that won't run them for more than 3 hours a day of full sun.

There are a LOT of variables here. For example, if your neighbor went with AGM or flooded lead acid batteries then that 600 ah battery bank only has a real world useable capacity of 300 ah. Also, how many solar panels and how much power is being used to recharge the batteries plays a role in this as well. With my small setup for example, I’m using 750 watts of solar panels to charge a 300 ah lithium battery bank. In the daylight hours, I can run an 8k BTU window unit all day long while running lights, a radio, recharging my cordless tool batteries, and still have enough leftover power to recharge the battery bank. I have left all of this running after the sun went down for 3 hours before going to bed, but the battery bank still had a decent amount of power still left.

[Bill M]

Series is correct. You need to run your panels the same as you run your batteries, which in this case is in series.

Thanks for the reply. That is what I was wondering.

First thing is first Bill. Go look at the tag on the back of your 25 watt solar panel. More than likely, it will say that the maximum voltage is going to be around 18-20 volts. If that is the case then that is going to be a “12 volt” panel. If the tag says 28-32 volts then that is going to be a “24 volt” panel.

If the panel is a 12 volt panel then the two panels will have to be wired in series to give 25 watts at 24 volts. If the panels are 24 volt panels then you can wire the two panels in parallel and get more amperage.

Wiring the panels in series will be the exact same as wiring the batteries in series. Simple connect a positive from one and the negative from the other together, then use the remaining positive and negative to connect to the charge controller.

Keep in mind that when you wire panels in series, your voltage will go up but the amperage will stay the same. Same goes for the batteries. With the panels when they are wired in series, if just one panel gets a little shade on it then the output of both panels will drop significantly. So make sure they are in a shade free area.

Thanks for the info in a way I can understand.

1.) Vmp is indeed 18V with Voc at 22.41V so I can not have 50 watts with these two panels @ 24V, correct?
2.) If I wired the batteries to have 24V, the panels likely couldn't keep up.
3.) If I wire the batteries in parallel and stay at 12V but put the panels in series, they would then be at 50 watts?
4.) If the answer to 3 is yes in both cases, I should have longer battery life, correct?

I got this at another site. It appears to be in conflict with your info if I read it correctly.

"It looks like the second attachment helps answer your question. The two big parameters are Open-Circuit Voltage (Voc) and Voltage at Maximum Power (Vmp).

For a single panel (or parallel) your VMP = 18volts and Voc = 22.41 for each panel.

In series your VMP = 36 volts and Voc = 44.82 volts

If the link is your manual check out section 2.2 for your panel requirements. Check the specific model you are looking at and compare it to the voltage and Voc in the table.

For all the models listed, it looks like you may be fine with either series or parallel, it makes it easy with only two panels. Since you want a 24-volt battery I would lean towards the two panels in series.

[91cavgt]

Thanks for the reply. That is what I was wondering.



Thanks for the info in a way I can understand.

1.) Vmp is indeed 18V with Voc at 22.41V so I can not have 50 watts with these two panels @ 24V, correct?
2.) If I wired the batteries to have 24V, the panels likely couldn't keep up.
3.) If I wire the batteries in parallel and stay at 12V but put the panels in series, they would then be at 50 watts?
4.) If the answer to 3 is yes in both cases, I should have longer battery life, correct?

Either way you wired the panels, you will still have 50 watts of power. One way will give you more amperage and the other will give you more voltage. But if you need to run 24 volts due to the pump’s requirements then the panels will have to be ran in series.

The big question is with your current setup, how is the battery life? If it is cloudy for a couple of days, does the pump stop working? Are you looking at add a second pump to get more flow?


EDIT: Sorry Bill, I misunderstood the first post you made. So you want to run the pump you already have at 24 volts to get a higher flow rate. By adding another panel and another battery, you will be ok. The panels will have to be wired in series, not parallel as the diagram you posted shows. Sorry for the confusion on my part.

[Bill M]

Either way you wired the panels, you will still have 50 watts of power. One way will give you more amperage and the other will give you more voltage. But if you need to run 24 volts due to the pump’s requirements then the panels will have to be ran in series.

The big question is with your current setup, how is the battery life? If it is cloudy for a couple of days, does the pump stop working? Are you looking at add a second pump to get more flow?


EDIT: Sorry Bill, I misunderstood the first post you made. So you want to run the pump you already have at 24 volts to get a higher flow rate. By adding another panel and another battery, you will be ok. The panels will have to be wired in series, not parallel as the diagram you posted shows. Sorry for the confusion on my part.

No problem. I have never had the pump stop, even with multiple cloudy days. It has slowed on me but that is it. I have been running on the same setup you helped me get going last year. I did expand the pond size last October. I discovered that I was only halfway cleaning the pump so I'm going to go full cleaning and see how the pumping goes. I may stay at 12V if the pump does well after that and just extend the battery life if I'm thinking correctly.

[91cavgt]

No problem. I have never had the pump stop, even with multiple cloudy days. It has slowed on me but that is it. I have been running on the same setup you helped me get going last year. I did expand the pond size last October. I discovered that I was only halfway cleaning the pump so I'm going to go full cleaning and see how the pumping goes. I may stay at 12V if the pump does well after that and just extend the battery life if I'm thinking correctly.

If you added another solar panel and another battery then it will definitely extend the run time. You could go ahead and buy the extra battery and solar panel, but wire it all in parallel if the pump puts out enough after getting cleaned. At that point, if it still does not flow enough then you could wire everything in series and get more flow. Just by adding another panel and battery, regardless of how it is wired, it will last longer.

[Bill M]

Thanks again for the reply. I have all the parts and plan to try to get it done before rain starts this evening. I charged the new battery and will charge the other once I disconnect it. I redesigned the previous drawing. I assume I can leave the panels wired in series even if I decide to stay at 12V (batteries wired in parallel)? I found an old shooting rail that was never put on a ladder stand years ago that I couldn't throw away and it will serve as the panel mount now. Pics later in this thread.

[Bill M]

For anyone wondering, the Epever controller allows me to have 2 timer settings. I have it start in the morning once light out and turn off for a couple of hours midday for no load charging. It starts again in the afternoon and shuts down just before dark. The cycle repeats the next day.