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  • Keeping the batteries from going to zero

    I installed a starter Renogy 400W system on my Reflection about 2 months ago (2 Battleborn batteries) and for the most part, all is going well. I'm staying in a location in Arizona where I'm getting plenty of daytime solar to satisfy my needs (most days). I can monitor my solar panels and batteries and as expected, during the day, the batteries get fully charged and at night, they drain down somewhat. I can power my needs with the exception of air conditioning and refrigeration most days. I handle the refrigeration with propane so I'm mostly content. At some point, I may want to add more panels and batteries to be able to handle refrigeration also but that's for a later date.

    The problem is that we have occasional rain days where the batteries don't get fully charged and then can't make it through the night. We also sometimes watch too much TV or use the microwave a bit too much. This can (and has) caused the batteries to run out. This only happens about once every two weeks. We have shore power available but not turned on unless we get into one of these situations or it gets really hot and I need air conditioning.

    What I'd like to do is set up the system so that I get an automatic boost from shore power when I'm about to deplete the batteries but only when we're getting into trouble. How can I set that sort of thing up?

    My system is set up with a transfer switch that accepts either the inverter or shore power as input and powers the rest of the trailer from there. This means that I'm essentially running either from solar/battery/inverter or shore power. The converter is configured so it's only used when shore power is on.

    What I'd like to see is my converter engage and put a bit more into the batteries when we're running low (but only then). The way I'm configured now, if I turn on shore power, I'm going to fully charge my batteries and then there is no where for the solar power to go during the day. I'd like to be able to do this so that the converter will engage when needed but not until then. Once the converter engages, I'd also like it to turn off before the batteries are completely charged so that the following day, the solar panels will do something meaningful.

    Is there some way to set up my shore power connection to automatically become active before the system reached a battery depleted shut down and then have it deactivate at some threshold so that I essentially switch back to solar/battery/inverter mode? Once again, this isn't needed daily, just occasionally.

  • #2
    Originally posted by KenBeccard View Post
    I installed a starter Renogy 400W system on my Reflection about 2 months ago (2 Battleborn batteries) and for the most part, all is going well. I'm staying in a location in Arizona where I'm getting plenty of daytime solar to satisfy my needs (most days). I can monitor my solar panels and batteries and as expected, during the day, the batteries get fully charged and at night, they drain down somewhat. I can power my needs with the exception of air conditioning and refrigeration most days. I handle the refrigeration with propane so I'm mostly content. At some point, I may want to add more panels and batteries to be able to handle refrigeration also but that's for a later date.

    The problem is that we have occasional rain days where the batteries don't get fully charged and then can't make it through the night. We also sometimes watch too much TV or use the microwave a bit too much. This can (and has) caused the batteries to run out. This only happens about once every two weeks. We have shore power available but not turned on unless we get into one of these situations or it gets really hot and I need air conditioning.

    What I'd like to do is set up the system so that I get an automatic boost from shore power when I'm about to deplete the batteries but only when we're getting into trouble. How can I set that sort of thing up?

    My system is set up with a transfer switch that accepts either the inverter or shore power as input and powers the rest of the trailer from there. This means that I'm essentially running either from solar/battery/inverter or shore power. The converter is configured so it's only used when shore power is on.

    What I'd like to see is my converter engage and put a bit more into the batteries when we're running low (but only then). The way I'm configured now, if I turn on shore power, I'm going to fully charge my batteries and then there is no where for the solar power to go during the day. I'd like to be able to do this so that the converter will engage when needed but not until then. Once the converter engages, I'd also like it to turn off before the batteries are completely charged so that the following day, the solar panels will do something meaningful.

    Is there some way to set up my shore power connection to automatically become active before the system reached a battery depleted shut down and then have it deactivate at some threshold so that I essentially switch back to solar/battery/inverter mode? Once again, this isn't needed daily, just occasionally.
    Welcome to Grand Design's Technical Forum. Besides the Battleborn and Renogy, what else is in your system? If you can draw out a diagram (doesn't have to be fancy) that will help tremendously.

    Especially important--what battery monitor do you have?

    Howard
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

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    • #3
      Welcome to the forum Ken. You pose a very interesting question. Most people will leave their converter connected when on shore power. But there's no reason to pull power from the grid when you have solar that will meet your needs.

      The Victron BMV-712 battery meter may meet your needs in two ways.

      1. You can program an alarm which tells you when the batteries reach a certain voltage level. If the alarm trips, then you are getting lower than the point you programmed and it's time to turn on your converter.
      2. The 712 has a relay function. With the proper wiring and relay set up, you could program the battery monitor to trigger a relay which will turn on the converter and charge the batteries. Of course, using this method would require some wiring ingenuity on your part.

      Jim
      Jim and Ginnie
      2024 Solitude 310GK
      GDRV Technical Forum Moderator
      GDRV Rally Support Coordinator

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      • #4
        TucsonJim: Using the BVM-712 sounds like a good clue. I'm still considering exactly how I could wire it but the 712 relay function could give me a starting point.

        I do leave the converter connected when shore power is on but I guess I'm really looking to run it in two modes: 1) When running fully from shore power, use the converter normally; 2) When running with solar/batteries, be able to use it for an emergency boost to the batteries.

        Right now, I have a transfer switch that can have both inputs (inverter or shore power) active and it will prioritize one over the other. I don't generally have both power sources active at the same time, however. I'm mostly using it as a safety device to make sure that shore power and the inverter don't power the main panel in the trailer at the same time (that would be ugly). What I typically do is turn on one of the sources at a time to manually decide which power source I'm running on. At any given time, there is only one of them active because I'm manually controlling it that way. If I mess up and power both at the same time, there's still no problem. I just don't typically do that.

        In order to get this emergency boost to work, however, I guess I'd have to have shore power active up to the transfer switch and use the switch to prioritize the inverter over the shore power. The problem with that is the converter then comes on which is counter productive. So, I have to put some sort of logic (with relays from multiple triggers) in place. I want the converter to be powered in two modes: 1) There is no inverter power; 2) There is inverter power and the battery voltage is low. In the first case, I'm running entirely on shore power and the converter is working as to its original intent. In the second case, I'm running on solar/batteries and I only want the converter to work in emergency mode.

        What I'd need is something like a relay that closes the power connection to the converter when there is no inverter voltage. I'd also need relays to close the power connection when I have both inverter voltage and a low voltage signal from the BVM-712 relay signal. Does that sound about right?

        This is all taking me back a few years. I have my degree in Computer Science and when in school, I used a breadboard with and/or/nor gates to create logic situations. Unfortunately, I'm not a EE so making the final leap into the practical hookups seems a bit daunting. I think I understand the logic of what I need but the actual wiring and acquiring the relays is a bit beyond what I'm comfortable with. There are both AC and DC inputs involved in making the relay connections, different voltages, etc. My training unfortunately stops at the logic of it all.

        It would really be nice if someone had a modicum of intelligence built into the converter. I don't suppose anyone has created one of those though?

        Comment


        • #5
          Howson: I use the Renogy BT-1 bluetooth connection from the solar controller that I use to monitor both battery power and solar power. Unfortunately, I don't have a drawing tool available to create diagrams. It's pretty straight forward, however. The solar panels hook to the controller which hooks to the batteries. The inverter hooks directly to the batteries and then provides one of the inputs to the transfer switch. The other input to the transfer switch is the shore power and I moved the power connection to the converter to the input side of the transfer switch so that it only runs on shore power. The output from the transfer switch goes into the main panel on the trailer.

          Comment


          • #6
            Originally posted by KenBeccard View Post
            Howson: I use the Renogy BT-1 bluetooth connection from the solar controller that I use to monitor both battery power and solar power. Unfortunately, I don't have a drawing tool available to create diagrams. It's pretty straight forward, however. The solar panels hook to the controller which hooks to the batteries. The inverter hooks directly to the batteries and then provides one of the inputs to the transfer switch. The other input to the transfer switch is the shore power and I moved the power connection to the converter to the input side of the transfer switch so that it only runs on shore power. The output from the transfer switch goes into the main panel on the trailer.
            Ken,
            Look at the diagram linked in this thread: https://gdrvowners.com/forum/operati...lts-f-350-mods

            Note how I tied in the relays to the incoming power. All the info about it is documented here: https://gdrvowners.com/forum/operati...er-overloading

            I have a BMV-712 ( TucsonJim and I were thinking along the same lines) but I have never messed with the relay function. Theoretically I don't see why you can't use a Sensata Solid State Relay, or SSR, (like I did) but use the BMV's relay function to trigger the SSR. The relay, obviously, would pass shore power to the converter.

            The key is programming the BMV to respond to battery voltage levels.

            Assuming that can be done, what I'd do is get an SSR that is normally closed. If the battery level is good, the BMV triggers the relay to open removing shore power. Should the BMV fail or turn off for some reason, the relay defaults to closed passing shore power to the converter.

            Again--that's all theoretical but it should work.

            There's much more detail to doing this right that I'm not including right now (heat sink, wire size, etc) as I'm not sure of how much you've worked with these types of components. (You may be more knowledgeable than me--lots of really, really smart folks here on this forum!)

            Hope this helps.

            Howard

            P.S. Victron's SmartShunt may be an option, too, Give it a look. Victron's bluetooth app (that supports either the BMV or SmartShunt) is fantastic.


            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

            2017 Ford F-350 DRW, '19 315RLTSPlus

            Comment


            • #7
              Originally posted by howson View Post

              Ken,
              Look at the diagram linked in this thread: https://gdrvowners.com/forum/operati...lts-f-350-mods

              Note how I tied in the relays to the incoming power. All the info about it is documented here: https://gdrvowners.com/forum/operati...er-overloading

              I have a BMV-712 ( TucsonJim and I were thinking along the same lines) but I have never messed with the relay function. Theoretically I don't see why you can't use a Sensata Solid State Relay, or SSR, (like I did) but use the BMV's relay function to trigger the SSR. The relay, obviously, would pass shore power to the converter.

              The key is programming the BMV to respond to battery voltage levels.

              Assuming that can be done, what I'd do is get an SSR that is normally closed. If the battery level is good, the BMV triggers the relay to open removing shore power. Should the BMV fail or turn off for some reason, the relay defaults to closed passing shore power to the converter.

              Again--that's all theoretical but it should work.

              There's much more detail to doing this right that I'm not including right now (heat sink, wire size, etc) as I'm not sure of how much you've worked with these types of components. (You may be more knowledgeable than me--lots of really, really smart folks here on this forum!)

              Hope this helps.

              Howard

              P.S. Victron's SmartShunt may be an option, too, Give it a look. Victron's bluetooth app (that supports either the BMV or SmartShunt) is fantastic.

              Sorry for the delayed response. I've had some internet issues for the last couple of days. Life for full timers.

              I understand your suggestion. I didn't make much sense of the diagrams but I get the concept. If the battery voltage is good enough (as identified by the BMV), it causes the SSR to open and it inhibits the power to the converter. That makes sense. The only thing I might add to that would be a manual bypass switch for when I'm using shore power exclusively so that the converter can run as it is normally intended.

              I did have another thought about this, however. When the converter comes on, it seems like it should raise the voltage on the battery connections a bit. It seems to me that If I'm only working with a single voltage (say 12.3V for example), the BVM would trigger the SSR to power the converter. That would instantly raise the voltage to say 12.5V and cause the BVM/SSR to shut the converter back off because the BVM would detect the new higher voltage and turn off the alarm. The batteries haven't necessarily received a charge but the voltage increases because of the converter. What I'd need to do is actually do is specify a range. The converter would need to engage at 12.3V and disengage at 12.7V for example. If I'm relying on a single triggering event (voltage drop to 12.3V), wouldn't I get a short cycle situation? Don't I also need a second trigger (other than the low voltage) to disable the converter?

              I guess I'd need to know more about the BVM capabilities. How does the alarm/relay function work? Do I have options to specify a range of voltages? Alarm on at 12.3V and off at 12.7V, for example?

              At this point, it's quickly becoming an academic exercise anyway because I don't have the expertise to know about heat sinks and such. I'm OK with this on a logical level but if the wiring is more complicated than attaching wires to components, We're getting past my expertise.

              Thanks for the responses once again.

              Comment


              • #8
                Originally posted by KenBeccard View Post

                Sorry for the delayed response. I've had some internet issues for the last couple of days. Life for full timers.

                I understand your suggestion. I didn't make much sense of the diagrams but I get the concept. If the battery voltage is good enough (as identified by the BMV), it causes the SSR to open and it inhibits the power to the converter. That makes sense. The only thing I might add to that would be a manual bypass switch for when I'm using shore power exclusively so that the converter can run as it is normally intended.

                I did have another thought about this, however. When the converter comes on, it seems like it should raise the voltage on the battery connections a bit. It seems to me that If I'm only working with a single voltage (say 12.3V for example), the BVM would trigger the SSR to power the converter. That would instantly raise the voltage to say 12.5V and cause the BVM/SSR to shut the converter back off because the BVM would detect the new higher voltage and turn off the alarm. The batteries haven't necessarily received a charge but the voltage increases because of the converter. What I'd need to do is actually do is specify a range. The converter would need to engage at 12.3V and disengage at 12.7V for example. If I'm relying on a single triggering event (voltage drop to 12.3V), wouldn't I get a short cycle situation? Don't I also need a second trigger (other than the low voltage) to disable the converter?

                I guess I'd need to know more about the BVM capabilities. How does the alarm/relay function work? Do I have options to specify a range of voltages? Alarm on at 12.3V and off at 12.7V, for example?

                At this point, it's quickly becoming an academic exercise anyway because I don't have the expertise to know about heat sinks and such. I'm OK with this on a logical level but if the wiring is more complicated than attaching wires to components, We're getting past my expertise.

                Thanks for the responses once again.
                Good questions and grasp of the issues.

                Instead of voltage the trigger event could be the SOC % (as measured by the BMV). It "knows" when the battery (or battery bank) is low and when it is fully charged.

                However, from the brief reading that I did on the topic, it isn't perfect as the BMV uses a "time to go" calculation. If you have varying loads (refrigerator for example) the TTG may vary dramatically, throwing off the calculation (and thus the relay trigger).

                Regardless, I have no idea how to program the BMV to trigger it's relay or if there's any other "gotchas". Beyond my knowledge and experience level.

                Thanks for the discussion--definitely interesting.

                Howard

                Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                2017 Ford F-350 DRW, '19 315RLTSPlus

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