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, how would a diagram look of this? I would appreciate any input from someone knowledgeable in solar electrical systems.

Edit: Drawing added

I read the part # from your picture - Is this the pump you are talking about?
https://www.amazon.com/12V-Brushless-Submersible-Fountain-Aquarium/dp/B01IAFCRF2?th=1


If so then your pump is 21.5 watts and you have a peak solar output of 50 watts. In very broad and lose terms (not considering your batteries). For every hour of peak sunshine, you get, you can run the pump for 2 hours.

If you need some specific help just DM me and we can probably clear this up in no time over a phone call.

Longer explanation of what is going on:

You have a couple of things going on here. Power generation (solar panels) and energy storage (batteries).

Power Generation:

During peak conditions; you are generating 50 watts of power. Power (watts) = Voltage * Current. From the two terms power and voltage, we can find the third 'current'.

Parallel Solar Panels: Current = power (watts) / voltage. Current = 50w / 12v Current = 4.167A

Series Solar Panels: Current = power (watts) / voltage. Current = 50w / 24v Current = 2.083A


Energy Storage:

Anytime you are generating more power than you are using the excess gets saved by charging your batteries. Depending on where you live and any obstacles you may only get ~4.5 hours of peak solar production a day. So you would want to generate at least the entire days' worth of energy usage in those 4 hours. Ideally a bit more. Generating more than you use when the sun is out and storing it in a battery is what lets the pump run when the sun goes down.

If the pump can be off in the dark, then you may not need batteries. if you want the pump to run, you need more panels.

A 24V / 10A charge controller needs 240 watts (plus a bit to make of for not being 100% efficient) to have maximum output.


*** Google Ohms law Calculator to go online and have it do the math for you you might also want to Google watt-hour calculator. ***

Thanks for your reply. This is indeed the pump being used. It does not run for 24 hours. The Epever charge controller enables me to have 2 start and stop times. It comes on in the morning after the sun is up, powers down midday for a time I'm able to control to recharge the battery, and then back on in the afternoon until a bit before dark. It has worked well for the past year at 12v using this. It would run on cloudy days also which surprised me a bit. The specs on the panels are below.

I don't believe I can DM with my account.

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.

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 withe 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.

Triple check the manual. I just skimmed. There may be something written before or after contradicting what I just wrote. The manual should override anything I say.

https://www.epever.com/wp-content/uploads/2021/04/XTRA-N-Manual-EN-V4.5ETL.pdf

I want to thank you for taking the time with this. I will look at the suggestions. I think I may be complicating a fairly simple process for this application.

No problem and don't sweat it

I am the king of overcomplicating things. I build things and do microcontroller projects for things I could buy off the shelf.

There is just a satisfaction that comes from doing things yourself.

I will set the panels up in series and according to the calculator you posted plus an Epever one at their site, I'll be good to go for this application. Thanks again.