Question about battery chargers

[Mike82]

I'm trying to design a small solar system to power a hydroponics system and have a question about battery chargers. My system will draw about 200 watts for 10 hrs per day. I was planning on a 24v rig using about 600 watts of PV for starters, a FA battery bank around 350-400 ah, 60A controller, 2k watt inverter (sized for potential expansion). My question has to do with back-up charging in case the PV don't supply enough power to the battery bank. For example, say the hydroponic system during its run-time drains the batteries to say 23.5 volts and there will be no further draw until after the panels do their recharging thing the next day. Is there a smart charger which can be made to not "turn-on" unless the power drops below 23.5v? Otherwise, the charger will be doing the recharging the panels during the night rather than the PV panels themselves. It's maybe a dumb question.. Thanks.

[DanKegel]

Do you have grid power you're going to use to run that battery charger?

Also, how does the 200 watts break down (e.g. circulation pump, heater, grow lights)? Any chance you could mimic natural daylight cycle and not run grow lights when the sun isn't shining, to reduce the size of battery you need?

[Mike82]

Do you have grid power you're going to use to run that battery charger?

Also, how does the 200 watts break down (e.g. circulation pump, heater, grow lights)? Any chance you could mimic natural daylight cycle and not run grow lights when the sun isn't shining, to reduce the size of battery you need?

Thanks for the response. I have grid power. Breakdown: 35w for the pump and 165w for the grow lights. I can only use sunlight during the winter months when the sun comes in the lanai, but even then it is only a supplement. I'm not too concerned about saving money on batteries as I plan using the battery back up for some rare short term power outages, plus I plan on expanding the system as additional funds become available.

[DanKegel]

I thought you were proposing to use batteries daily to run the grow lights and pump when the sun wasn't shining?

If you can run the grow lights only when the solar panels are producing, such that they never draw power from the batteries, it'll save a lot of wear and tear on batteries.

[Mike82]

I thought you were proposing to use batteries daily to run the grow lights and pump when the sun wasn't shining?

If you can run the grow lights only when the solar panels are producing, such that they never draw power from the batteries, it'll save a lot of wear and tear on batteries.

With hydroponics the pump needs to stay on 24/7 to keep the roots from rotting. The lights need to stay on a set time each day in order to maximize growth. The system will be running during daylight hour, so the batteries will be supplying the power concurrent with the panels charging the batteries, unless there is a way to have the panels run the lights and automatically engage the batteries when the light is insufficient to provide the needed power.

[Amy@altE]

You could put the AC charger on a timer to only go on at night. Alternatively, if you have a charger that is adjustable, you could set it to a lower voltage than the solar charge controller, so it will only come on when the solar charge controller is not on. For example, if float for the solar is 27.4V, then set the AC charger to come on at 27V.

[Logan005]

forget the solar, get a nice fixed smart charger, to maintain your 24 volt batteries and Loads, Your aquaponic set up will run 24 hours a day and will run several hours after grid fail. after you have done this you can add solar for daytime power w/o cycling your batteries.

[Mike82]

You could put the AC charger on a timer to only go on at night. Alternatively, if you have a charger that is adjustable, you could set it to a lower voltage than the solar charge controller, so it will only come on when the solar charge controller is not on. For example, if float for the solar is 27.4V, then set the AC charger to come on at 27V.

Thanks. Who makes an adjustable charger like the one you described, or maybe an inverter/charger?

[Mike82]

forget the solar, get a nice fixed smart charger, to maintain your 24 volt batteries and Loads, Your aquaponic set up will run 24 hours a day and will run several hours after grid fail. after you have done this you can add solar for daytime power w/o cycling your batteries.

That's a good idea! I could divert some of the funds I would have spent on the panels/controller and apply them toward a better charger or inverter charger. Any recommendations on what to look at?

[Logan005]

I use a Samlex 2415, but I do not use solar in this application. If I did, I would use a wall timer to maximize daytime solar power usage with minimal battery cycling.

[DanKegel]

Have you considered putting in skylights (maybe SolaTubes)?

Another idea: run the pump from the grid, run the grow lights straight from solar panels (if that works - you'd need to research it; see e.g. https://www.solarpaneltalk.com/forum...eries-inverter ), and forget about batteries altogether.
What model grow lights?

If you feel like you need grow lights when the sun isn't shining, run them from the grid then. (Might need a separate set of lights.)

That'd keep your grid usage down without spending any money at all on batteries.

[Sunking]

Thanks for the response. I have grid power. .

Then you have no use for solar and would be very foolish to do so.

What you are asking for is paying 5 to 10 times more than what you can buy power from the utility for the rest of your life. You cannot save any money using off-grid solar, and it makes you a heavy polluter.

If you are worried about power outages, you have no use for solar either. Just use a smaller less expensive set of batteries and a AC charger. When the power goes out, the batteries take over until power is restored.

[Mike82]

Then you have no use for solar and would be very foolish to do so.

What you are asking for is paying 5 to 10 times more than what you can buy power from the utility for the rest of your life. You cannot save any money using off-grid solar, and it makes you a heavy polluter.

If you are worried about power outages, you have no use for solar either. Just use a smaller less expensive set of batteries and a AC charger. When the power goes out, the batteries take over until power is restored.

Hi Sunking: I realize that. It's more of a hobby, learning experience and a project for my kids as well as a back-up for power outages.

[Sunking]

Hi Sunking: I realize that. It's more of a hobby, learning experience and a project for my kids as well as a back-up for power outages.

A system that is capable of 2 Kwh per day is not a learning tool or toy. You are looking at $4000 to $6000 and $2000 of that is a battery that needs replaced every few years. That is the lesson you will learn. I am just trying to make sure you understand what you are asking for. Now that you know, I could careless what you do. Heck if I were vested, I would be trying anything I could to sell you the equipment. I would tell you exactly what you want to hear. But I am not vested, so that only leaves me with the facts.