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Running Load ONLY While the Sun is Shining?

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  • #16
    Yes there are some of those that are programmable so you can set the voltage they turn on at.
    9 kW solar. Driving EVs since 2012

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    • #17
      Sun is perfect between 9-10am for two panels on garage. I'm going to run my LG clothes washer off solar with no charge controller or battery. Just an inverter to double the panel voltage. I'll use a shunt regulator to keep the panel voltage stable for the inverter. The excess energy will go to the water heater and it has extremely fast response to adjust for load changes. Determining if a panel can supply a load is tricky. Often best done with a small pilot panel which is loaded with a resistor low enough that it will never reach power point voltage. You can get one of those digital voltage relays for only $13.

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      • #18
        > I'm going to run my LG clothes washer off solar with no charge controller or battery. Just an inverter to double the panel voltage.

        You may find that even with being overpaneled a bit, and using an inverter washer, there may be surges that trip it off line, I hear my XW humming and playing a beat when the washer is running, mostly when it reverses direction.
        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

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        • #19
          Bala - I was originally thinking about VSRs, and after more research on them, I' think you've hit the nail on the head, but for a different reason than I thought.

          Simply, I didn't realize the 'vehicle' VSRs could be used for non-battery devices.

          So, right now I'm thinking about two of them. One would switch on and power a 12-12v trickle charger that would top-up three batteries (two motorcycles and the trailer electric brake backup battery) that are wired in a parallel configuration. These batteries will never need much more than a top-up to keep them maintained, and using the lower amperage trickle charger will mean that I can string out modest sized wires to easily connect and disconnect them. The second VSR is for the same purpose as you've described... powering a couple of very low wattage ceiling circulating fans that manage trailer temps during the hottest months. I'll really only use one if they non-adjustable, but if I can find a Vin-adjustable one, then that one with the fan will be set higher than the battery charger so it only kicks the fans on when the sun is really blazing.

          These will be easy to wire onto the main bus of the primary battery system, they're reasonable cost-effective, and now appreciating that they can really be used to wire in any load you want, I can actually control a slew of equipment.

          Thanks for the advice!

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          • #20
            OK, I just finished typing my response to Bala, only to suddenly consider that if it's sitting on the battery side of a solar controller, won't the VSR eventually stop working?

            Here's where I really need someone's "solar controller" expertise... the reason I'm concerned is that I thought a solar controller will actually cut the voltage output once it senses that the primary batteries are at a top-up voltage (like a trickle charger)... I'd think this would mean that the VSR would never see the higher voltage it needs once those are charged... or it would flick on and off as the solar charger only occasionally trickle charged the primary batteries.

            Any thoughts here? Will a VSR still work, or am I right to be concerned?

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            • #21
              I have a low cost basic VSR here, it has a cut in V of 13.2 and a cut our V of 12.8.

              You solar controller will have a few charge settings but will have a float setting above 13.2V, as long as there is enough sun to the panels and not to much current draw it will stay in float.

              At some point in the afternoon/overnight your batteries will drop below 12.8 so the VSR will cut out, then the next morning if the panels can charge them back up to 13.2 the VSR will cut back in.

              The only issue I see is if there is not enough panel charge to hold the battery voltage above 12.8 once the load comes on. It may cycle back and forth a bit but that should not hurt anything.

              I did see an adjustable VSR but it was expensive, you may also be able to find one with a higher cut in V.

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              • #22
                You set your trigger voltage to your Absorb voltage, and connect it to the panel (if using a PWM controller) Once the battery reaches Absorb voltage, the relay will kick in, and power your other loads, when it goes to float, your PV voltage will increase and keep the relay on till something lowers the voltage below Absorb.

                if using a MPPT controller, you have to play around with the voltage, and set it for something a tad higher then Your array Vmp (which will vary over temperature). As the controller unloads the panels, their voltage will rise and trigger your relay.
                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

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