AGM Battery Recommendation Request

[guardian]

Hi All,
I am looking to run two Tower Gardens (bayuk.towergarden.com) on only panels and batteries. The towers run on small water pumps that are 50 watts each, 100 watt total. These pumps go through a mechanical timer (http://waterheatertimer.org/pdf/Tork-601A-Manual.pdf). I was advised and bought a 100 watt monocrystalline panel, Sunsaver 6L charger, a Bestek 1000 watt inverter and a 35ah AGM battery. The battery recommendation was inadequate. I run the pumps on and off at night, for a total of 3 hours. Here in south FL, this routinely runs the battery into the yellow zone on the charger, which I understand will drastically shorted the battery life. It's been rainy lately, so this doesn't help.
My question - what would be a better ah rating for this setup? Your advise about this, and any other comments on my setup, would be greatly appreciated. Thanks!
Regards,
Andrew

[Mike90250]

Sadly, as you found out, it's not easy to recommend solar gear till you have a complete understanding of it's limits, and the intended application. At first glance,
the inverter is too large and will waste a fair amount of power (like driving a SUV 2 blocks to buy a pack of smokes)
The battery is too small
And likely, the PV panel is too small.

To properly figure this out, how many hours total (in a 24 hour day) do the pumps run ?
Your timer is a electrical-mechanical timer, and needs power 24/7 to run it's little clock motor, a mechanical timer has a wind up spring
We need your rough location, so the wintertime sun hours can be calculated, and that is used to size the PV panel array,

My rough guess is going to be 3 hours of pump at night, and another 6 hours in the day, for a total of 9 hours of 100 watts. That's 900 watt hours
I'd suggest a much smaller, efficient inverter like a Morningstar SureSine, good for 300w load, and very efficient. it's also going to let the motors in the pumps and timer last longer.
900w load needs a 2700wh battery (3x the daily load) at 12V, that is a 225ah battery, roughly 2, 6V 200ah golf cart batteries wired in series.

Another guess at a PV panel, to harvest 1400wh in 3 hours of good light, is about 600 w of PV panel, producing 40a through the charge controller. Summer time, you will have extra power, if you have more good sun in winter, you can use less PV also

So, the less hours the pump runs, the smaller the system can be.

The basis for some of my off-the-cuff wild guess, comes from the stickies here (on how to size a system)
https://www.solarpaneltalk.com/forum...or-camping-etc

[Logan005]

I have run 2 solar ponds for a lil over 2 years now. I have gone thru several Gel and AGM batteries. If you are experimenting for personal knowledge it will be an expensive learning experience. If you are doing this to save money, you will lose. If you have grid available don't waste your money on an expensive solar battery system, If all you need is backup power in the event of grid failure, then build a backup system or a hybrid system with grid tie feedback. anything off grid cost 4 to 10X as much per watt and is a heavy pollution producer. My large pond was just reconnected to the grid with an AC pump. my smaller pond is a lil further from the nearest outlet, still cheaper to have a qualified electrician to install an AC outlet than to use solar with batteries.

[guardian]

Thank you Mike.

That is exactly the info I was looking for. Actually, that seems like a lot of equipment and expense for such a small need. My location is west of Ft. Lauderdale, FL, and I do run the pump for a total of 9 hours in a 24 hour period. Try as I may to weigh through the documentation, I cannot find out the draw for that mechanical timer. But, I think that your estimates seem to be close enough. I am waiting on a 75ah am battery, so it would likely suit me better to get 2 more of those to get to the proper battery capacity you've suggested. And, I will get a pure sine wave 300 inverter, thanks for that advice.

6 panels sure seems like a lot. The one 100 watt panel I already have is monocrystalline. Do you see any reason to not get polycrystalline for the remainder of the panels?

[SunEagle]

Thank you Mike.

That is exactly the info I was looking for. Actually, that seems like a lot of equipment and expense for such a small need. My location is west of Ft. Lauderdale, FL, and I do run the pump for a total of 9 hours in a 24 hour period. Try as I may to weigh through the documentation, I cannot find out the draw for that mechanical timer. But, I think that your estimates seem to be close enough. I am waiting on a 75ah am battery, so it would likely suit me better to get 2 more of those to get to the proper battery capacity you've suggested. And, I will get a pure sine wave 300 inverter, thanks for that advice.

6 panels sure seems like a lot. The one 100 watt panel I already have is monocrystalline. Do you see any reason to not get polycrystalline for the remainder of the panels?

It doesn't matter if the panels are Mono or Polycrystaline. You will still need at least 500 watts or more to generate your daily usage of 900 watt hours.

Also if you go with 3 of those 75Ah 12 volt AGM batteries to create a 225Ah system you will be spending more money that using 2 x 6V 225Ah FLA batteries. You also run the risk of not evenly charging or discharging 3 batteries wired in parallel then 2 x 6volt in series.