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Is this possible??? Two Batteries, One Solar Panel and a USB Device...???

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  • Is this possible??? Two Batteries, One Solar Panel and a USB Device...???

    Hi,

    After the moment i have one solar panel, connected to a solar controller attached to a deep cycle 12V battery and a device connected to the Controller Output to a 12V to USB converter connected to a 5V device running 24/7 for about 4 days and then the charge controller stops output when battery is low.

    I want to increase the duration by adding another battery (different brand and Ah)

    Here's the idea:

    Purchase another Solar Controller. Output from Solar Panel split to go into two Charge Controllers. (so both batteries are getting charged seperately). Then combine both outputs of the two Charge Controllers into One Output (same voltage, but presumably the combined Ah of both batteries) and connect to 12V to 5V converter to my 5V device = longer run time?

    Is this correct and the safest way... Safest as in the two batteries are different and i don't want to connect them in parallel to cause any problems whilst being charged...

    Will this work?

    Thanks

  • #2
    If your battery is dying, this tells me you need more solar panels. It could also be a improper sized battery.

    How big is this panel, and how much unobstructed sun do you get a day? How may AH is the battery and what type, like flossed lead acid deep cycle?

    A 12 volt USB charger can pull up to 2 amps from a battery. It’s probably less because that 2amps is sent out at 5 volts.

    Comment


    • #3
      I would start by checking the efficiency of your 12V to 5V converter. These small devices
      can be terribly inefficient. If the 5V output current measures about the same as the 12V
      input current, it is a linear reg just burning up 7V (more than you use).

      If the 12V input POWER (V x I) is about the same as the 5V output POWER, you have an
      efficient switcher. if not, look into changing to one and avoid doubling 12V battery AH.
      Bruce Roe

      Comment


      • #4
        If your battery is dead after 4 days, your solar charge is insufficient. You need more panels About 8x as much as you have now
        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
          USB controller.jpg
          Many inexpensive charge controllers come with 5 volt USB output's
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

          Comment


          • #6
            Originally posted by littleharbor View Post
            USB controller.jpg
            Many inexpensive charge controllers come with 5 volt USB output's
            Already tried that...

            I already have one of those and use it. However if you plug the USB device in the USB socket on the controller, there is no circuit on the controller to detect low voltage detection on the USB output, it drains the battery totally. Hence why i used the output of the controller rather than the inbuilt USB Socket...

            Panel size aside, what about my idea of combining the outputs of 2x controllers into one OUTPUT = 12V plus higher Ah, can that cause any problems?
            I'm also waiting on a USB timer so that once it gets to 4 days of use, i switch off the USB device to give the battery a chance to charge back up...

            Can you think of any other solutions? Of course i will keep an eye out for an extra Solar Panel, any extra Charge is obviously welcome especially during dull overcast days.

            Comment


            • #7
              Originally posted by sharpharp View Post

              Already tried that...

              I already have one of those and use it. However if you plug the USB device in the USB socket on the controller, there is no circuit on the controller to detect low voltage detection on the USB output, it drains the battery totally. Hence why i used the output of the controller rather than the inbuilt USB Socket...

              Panel size aside, what about my idea of combining the outputs of 2x controllers into one OUTPUT = 12V plus higher Ah, can that cause any problems?
              I'm also waiting on a USB timer so that once it gets to 4 days of use, i switch off the USB device to give the battery a chance to charge back up...

              Can you think of any other solutions? Of course i will keep an eye out for an extra Solar Panel, any extra Charge is obviously welcome especially during dull overcast days.
              A second charge controller may not be what you need to fix your issue. It still comes down to how much charging amps your panel can produce and is it enough for 1 or 2 batteries.

              What are the Imp and Vmp ratings of your panel?

              Adding more batteries without adding more charging amps can be a disaster for the batteries.

              Comment


              • #8
                Originally posted by SunEagle View Post

                A second charge controller may not be what you need to fix your issue. It still comes down to how much charging amps your panel can produce and is it enough for 1 or 2 batteries.

                What are the Imp and Vmp ratings of your panel?

                Adding more batteries without adding more charging amps can be a disaster for the batteries.

                Hi,

                The solar panel is a 50w flexible panel with 17.6v Vmp and 2.84A Imp. The Deep Cycle battery is a 90Ah Varta. The other battery is a regular car battery at 60Ah.
                I know very little about the maths behind it all, so would appreciate the advice on this.

                Initially i set this up this system in a Shed to power an LED light with a switch, so the battery was always topped up and only used 0.5% off the time.
                Now i want to harnass that battery for running a USB device. I have ordered a USB volt meter to figure out the amount of amps the USB device i want to power 24/7 provides, so i'll post that when i have the figures.

                This morning the USB device had ran for 4 days straight. The controller disconnected the output as the battery was showing at 10.9V. I left the battery charging for around 6 hours and it was up to 11.2V

                Without knowing the draw of the USB device, I guess it's hard to advise whether I need a Bigger/more panels or more batteries.
                Is there a way of using battery 1 and when that gets low, auto switch to using battery 2 (whilst battery 1 charges up?

                Again, not that a savvy on solar and stuff, so go easy.

                Comment


                • #9
                  Originally posted by sharpharp View Post


                  Hi,

                  The solar panel is a 50w flexible panel with 17.6v Vmp and 2.84A Imp. The Deep Cycle battery is a 90Ah Varta. The other battery is a regular car battery at 60Ah.
                  I know very little about the maths behind it all, so would appreciate the advice on this.

                  Initially i set this up this system in a Shed to power an LED light with a switch, so the battery was always topped up and only used 0.5% off the time.
                  Now i want to harnass that battery for running a USB device. I have ordered a USB volt meter to figure out the amount of amps the USB device i want to power 24/7 provides, so i'll post that when i have the figures.

                  This morning the USB device had ran for 4 days straight. The controller disconnected the output as the battery was showing at 10.9V. I left the battery charging for around 6 hours and it was up to 11.2V

                  Without knowing the draw of the USB device, I guess it's hard to advise whether I need a Bigger/more panels or more batteries.
                  Is there a way of using battery 1 and when that gets low, auto switch to using battery 2 (whilst battery 1 charges up?

                  Again, not that a savvy on solar and stuff, so go easy.
                  Well the math states that to keep a 90Ah battery happy it needs about 7.5 to 11.5 charging amps. So without a doubt that 50watt panel will not even keep one of your batteries happy or properly charged.

                  Plus just stating you have an LED light is not enough info. What is the wattage and how many hours a day will you keep it lit? By adding the USB charging to the load you probably have drainned the battery. A second charger is not the solution. And running a battery below 12V is usually a quick death sentence for it.

                  Based on those charging amps you need about 200watts of solar panels just for the 90Ah battery. But without knowing what your USB charging uses in Watt hours per day makes it a little hard to properly size your battery and solar panel wattage.

                  Comment


                  • #10
                    Originally posted by SunEagle View Post

                    Well the math states that to keep a 90Ah battery happy it needs about 7.5 to 11.5 charging amps. So without a doubt that 50watt panel will not even keep one of your batteries happy or properly charged.

                    Plus just stating you have an LED light is not enough info. What is the wattage and how many hours a day will you keep it lit? By adding the USB charging to the load you probably have drainned the battery. A second charger is not the solution. And running a battery below 12V is usually a quick death sentence for it.

                    Based on those charging amps you need about 200watts of solar panels just for the 90Ah battery. But without knowing what your USB charging uses in Watt hours per day makes it a little hard to properly size your battery and solar panel wattage.

                    Hi,

                    USB Volt meter turned up today: The USB device is running at average 1.7A, 8W and 5.04V

                    I've ordered a 100W Solar Panel to add to the existing 50W.

                    Armed with the above info, can you suggest if this provides any info?

                    If not running the USB device 24/7, what would be a good compromise based on the above figures?

                    Comment


                    • #11
                      There’s good ways and bad ways to add mismatched solar panels. Best to add like panels to include wattage, voltage and amps. You can add mismatched panels if some math is followed. I like this article:

                      https://solarpanelsvenue.com/mixing-solar-panels/
                      Last edited by chrisski; 02-26-2021, 02:55 PM.

                      Comment


                      • #12
                        Originally posted by sharpharp View Post


                        Hi,

                        USB Volt meter turned up today: The USB device is running at average 1.7A, 8W and 5.04V

                        I've ordered a 100W Solar Panel to add to the existing 50W.

                        Armed with the above info, can you suggest if this provides any info?

                        If not running the USB device 24/7, what would be a good compromise based on the above figures?
                        Great. So the USB will burn 8 watts for each hour it is on. You can now calculate how many watt hours your loads will use each day.

                        Adding a second panel that does not match the first one may cause an issue if the Vmp and Imp are more than 5% different.

                        I think that chrisski posted a web page that can help with using both panels wired the best way that you can.

                        Comment


                        • #13
                          Originally posted by chrisski View Post
                          There’s good ways and bad ways to add mismatched solar panels. Best to add like panels to include stage, voltage and amps. You can add mismatched panels if some math is followed. I like this article:

                          https://solarpanelsvenue.com/mixing-solar-panels/
                          That page won't load: Error 520 Web Server is returning an unknown error

                          Comment


                          • #14
                            Loads for me. When I get a 520 or maybe 420 error, not really sure, I refresh the page and it works.

                            My point to putting the link up is to give math to support a statement, “Except in a very narrow circumstances, different sized panels on the same string is not a good idea.”

                            A google search for “how to calculate mismatched solar panels,” usually brings the article up.

                            As a spoiler, hooking a 50 watt to 100 watt panel depending on configuration would limit panel output to the lowest of the series, or in your case you may end up the same output with both panels or slightly less than the 100 watt panel by itself.

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