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Effect of batteries in a solar pump system

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  • Effect of batteries in a solar pump system

    After running a solar pump system on my ranch for a couple of years I decided to look into putting some deep cycle RV batteries in to, hopefully, get an extended run time out of each day of pumping. After doing some research and continuously "rattling the tree" of the techs from the company I bought the system from it was finally admitted that, #1, the controller/regulator runs the pump off the batteries ALL the time when there are batteries installed and, #2, this results in a 15% to 20% reduction in the daily water production due to the time it takes to charge the batteries back up in the morning.

    This seems completely backward to me as I thought the batteries would be charged during the day and discharged after the Sun no longer gave enough light to produced power through the panels. Is it normal for solar pump systems to work like this?

  • #2
    Sounds like the batteries and solar panels aren't sized large enough to handle the pump load.

    Comment


    • #3
      So making assumptions on the little inof you posted.

      You had a system that pumped water when the sun was shining enough and now have added only batteries and controller.

      This is basically what could be happening. Your panels are sized to run the pump only, there is not enough panel to run the pump and charge the battery.

      The controller system would have low voltage disconnect to prevent the batteries draining to much after the sun goes down.

      Then a Voltage setting that needs to be reached when the sun comes back up the next morning before the pump will start up.

      At the moment all you really have is a buffer for when cloud passes.

      You need the original panel sizing to run the pump plus more panels to charge the battery.

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      • #4
        Originally posted by Bala View Post
        ..........

        At the moment all you really have is a buffer for when cloud passes.

        You need the original panel sizing to run the pump plus more panels to charge the battery.
        That's what I would have said !!
        Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
        || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
        || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

        solar: http://tinyurl.com/LMR-Solar
        gen: http://tinyurl.com/LMR-Lister

        Comment


        • #5
          Being underpowered is basically the conclusion I've come to a while back. For that reason I've put new panels that boost the wattage output from 200 to 300w, which has helped, but water production still halts whenever a cloud comes over. The pump's operating depth is almost as deep as the company said it would go - 145 feet plus a little more to get into the tank - but has always pumped really well in good Sunlight.

          The current panels are stationary facing the South as prescribed for our location so I was wondering, since I still have the 2 old 100w panels, could I set those facing the rising Sun on a new mount with a voltage regulator controller set for the same parameters as the proprietary controller that originally came with the system and have the old panels dedicated to charging batteries in conjunction with the new panels charging the batteries as well as running the pump? Both panel sets would be basically in parallel with the batteries in the middle. I think this may also allow for batteries of higher amp-hour ratings (the company offered 55 a-h batteries) but experimentation would have to be required, I think. As long as the charging rate doesn't exceed 10 amps would the batteries be charged at a safe maximum rate to allow the pump to begin operation sooner in the mornings? The old panels are not matched with the new ones in terms of voltage and amperage so I thought putting them on their own regulator would remedy this mis-match as they charge the batteries.

          Both regulators would be set to stop charging at the same voltage level and the Eastern facing panels would stop working as the Sun moves away from them during the day leaving the batteries charged for the evening.

          But still, I have the question in mind as to whether or not other systems like Lorentz or Gundfoss follows this same manner of function by running the pump off the batteries all the time thus delaying the start up time in the morning? I had always thought the charging function was separate from the pumping and the batteries would take over when the panels quit producing power to run the pump. I guess that assumes adequate power to accomplish both tasks, though.

          Comment


          • #6
            I am wondering what the open circuit voltage of your panel setup is, and what voltage
            they typically operate at under good sun? Agree with the above, my conclusion is that
            adding batteries is an extremely poor cost tradeoff way (not to mention the maintenance
            issues) of increasing production.

            My take is yes you need more panels, what you have will only be effective under best
            center day hours and no clouds. That is exactly the situation I had here, and I remedied
            it with more panels, and no batteries or other additional equipment. My fix is to point a
            set of panels facing the rising sun, and another facing the setting sun, angled so they
            overlap production mid day. These panels are tied directly in parallel, the voltage will
            never rise above the open circuit voltage no matter how many panels you use, and the
            pump will take the current it needs over a longer day. Output will be up under clouds as
            well with the light dispersed to all directions. With perhaps 3 times the panels, your pump
            will not even slow down under light clouds, run at reduced rate under somewhat more
            severe clouds, and in general run for a longer productive day. Bruce Roe
            Last edited by bcroe; 06-19-2020, 09:34 PM.

            Comment


            • #7
              To the above here are some curves made here at 42 deg Lat. Power under sun was maxed for 8 hours straight on
              bottom curve, would have been even longer except for shadows using multi direction panels in parallel. At top is a
              measurement with panels elevated 61 deg facing E and W. When tied in parallel, the total power
              (1 + 3) ​​​​​stays close to constant all day. Power under clouds though reduced, will be more. Bruce Roe

              PVm17Jn16.jpg

              NScurJn17.jpg

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              • #8
                Thanks to everyone that's posted so far. I'll look at these graphs and such later this afternoon but I need to get over to the ranch to haul some water to try and get ahead of the situation.

                One thing, though, I've checked my notification settings and verified that I am supposed to be getting e-mail notifications whenever someone answers me but no e-mails have been forthcoming. Is this service not functioning here?

                Comment


                • #9
                  Bruce,

                  Did you build your panel racks yourself or are they a factory construction? The fact they are offset to track the Sun intrigues me. I'm assuming you took manual readings on the panel outputs over time as well?

                  I'm at 31 degrees N. latitude.

                  Here's the side-by-side images of the labels on the panels. The left image is the new panels, the right the original ones.

                  IMG_1131.JPG

                  Comment


                  • #10
                    Originally posted by Goat Rancher View Post
                    Bruce,

                    Did you build your panel racks yourself or are they a factory construction? The fact they are
                    offset to track the Sun intrigues me. I'm assuming you took manual readings on the panel outputs over time as well?

                    I'm at 31 degrees N. latitude.

                    Here's the side-by-side images of the labels on the panels. The left image is the new panels, the right the original ones.
                    Here at 42 Lat its all custom construct, latest changed seasonably for best energy and to
                    reject snow. Mostly 6061 aluminum and 18-8 stainless bolts, concrete foundation, but
                    one is treated wood which looks to last at least decade. More pictures available.

                    Graphs made over half a year for various arrangements, a well performing sample shown
                    above. Here 3 single test panels with variable elevation shown.
                    Bruce Roe

                    Test3dir.jpg

                    Comment


                    • #11
                      Hi, sorry to take so long in answering. We went on vacation and are back.

                      Is that a regulator on the frame holding the panel just below the panel's wiring module? If not I was wondering how far a panel's output would transmit before coming to a regulator since you have quite a bit of distance between individual panels there?

                      That is a very good, straight forward mount for your panels. Unfortunately I'm going to have to figure out something to mount panels higher as my goats love to chew on anything. I found the sensor line for the well's water level was chewed through to the wire yesterday. Why the goat stopped when it got to the wire I'll never know, especially since it's a tiny 22 gage multi-filament one. Breaking that circuit would have made the regulator think the well water was too low and shut it down. I'd built and placed a box for batteries under the panels so now they can stand on it and nibble. Didn't think about that when I placed it. I tried wrapping the wire cluster in barbed wire but they'll get through to something they're curious about any way they can. I think a large PVC pipe cut in two lengthwise to wrap around the entire wiring cluster will work well enough to stop it.
                      Last edited by Goat Rancher; 06-30-2020, 11:33 AM.

                      Comment


                      • #12
                        Originally posted by Goat Rancher
                        . Is that a regulator on the frame holding the panel just below the panel's wiring module? If not I was wondering how far a panel's output would transmit before coming to a regulator since you have quite a bit of distance between individual panels there?

                        That is a very good, straight forward mount for your panels. Unfortunately I'm going to have to figure out something to mount panels higher as my goats love to chew on anything. I found the sensor line for the well's water level was chewed through to the wire yesterday. Why the goat stopped when it got to the wire I'll never know, especially since it's a tiny 22 gage multi-filament one. Breaking that circuit would have made the regulator think the well water was too low and shut it down. I'd built and placed a box for batteries under the panels so now they can stand on it and nibble. Didn't think about that when I placed it. I tried wrapping the wire cluster in barbed wire but they'll get through to something they're curious about any way they can. I think a large PVC pipe cut in two lengthwise to wrap around the entire wiring cluster will work well enough to stop it.
                        Those 3 new, isolated panels are strictly for collecting curve data, they are not
                        connected to any system. Although the lot is neither rectangular or flat, I did
                        survey it pretty accurately per the locating stakes. In theory the panel outputs
                        should be measured by 3 MPPT systems, I did not want to bother with those.
                        Instead each panel output is simply shorted, producing a current about 25%
                        larger than at MPP, but directly proportional. That current was measured by a
                        0.1ohm current shunt which you see plugged into the panel.

                        I went out with a DVM by the clock on a very sunny day to record each curve.
                        The test panel support structure was only designed to last half a year, in fact
                        one of them fell down later. But the elevation angle was easily changed.

                        I tried several different panel mount schemes, one cheap treated wood, the
                        last (see SUN HOURS about section 20) is in serious concrete with 6061
                        aluminum and 18-8 SS bolts, set up to increase energy as well as minimize
                        snow efforts with seasonal tilt changes. Experience here is about the only
                        thing critters do not chew through is metal, but in your case it might need to
                        be thick. good luck, Bruce Roe

                        NS6motst.JPG24Rear.JPG

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