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  • hello from ontario

    My name is Billy i live on my 200 acre farm in central Ontario with my girlfriend and our GSD and chickens. I am working on my solar system as I can afford it. I have a 300 watt 48vdc panel now, with 4 car batteries and a cheap MIJ charge controller. It seems the charge controller wont work when I connect the battery bank in 48 volts, but will pass voltage when its connected either 12vdc or 24vdc. I had it at 12 vdc for an hour or so, as the sun came up it started to bring the voltage up too high, so i shut it down. connecting it at 24 VDC will pass current too, but just not at 48vdc. am I doing something wrong? or should I just scrap this 80 dollar controller and get something decent?
    Billy D

  • #2
    Hello Billy_d and welcome to Solar Panel Talk

    It sounds like that charger may not be rated for 48volt battery systems. Can you provide more information such as the make and model number.

    Also provide more information on that 300w 48vdc panel and batteries. Once we know more about your system we can hopefully help you.

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    • #3
      I doubt that one panel will put out enough voltage to charge at 48V.

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      • #4
        Originally posted by AzRoute66 View Post
        I doubt that one panel will put out enough voltage to charge at 48V.
        Maybe or maybe not, but I did just see a 115watt panel PVT115 made by Caterpillar that had a Vmp of over 70v so it may be possible to have 48v from a 300 watt panel.

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        • #5
          Many thin film panels are high voltage. There are also 96 cell silicon panels that put out high voltage, though not a 48 volt "nominal" voltage. which would be around 72 Vmp, 92Voc.
          2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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          • #6
            Originally posted by Billy_d View Post
            My name is Billy i live on my 200 acre farm in central Ontario with my girlfriend and our GSD and chickens. I am working on my solar system as I can afford it. I have a 300 watt 48vdc panel now, with 4 car batteries and a cheap MIJ charge controller. It seems the charge controller wont work when I connect the battery bank in 48 volts, but will pass voltage when its connected either 12vdc or 24vdc. I had it at 12 vdc for an hour or so, as the sun came up it started to bring the voltage up too high, so i shut it down. connecting it at 24 VDC will pass current too, but just not at 48vdc. am I doing something wrong? or should I just scrap this 80 dollar controller and get something decent?
            Billy D
            What loads are you planning to power from this system?

            Do you have normal grid power available?

            If I were you I would take a break at this point, clarify my goals and try to plan it out before spending any more money on it.

            Building such system piecemeal way will make you lose significant money on throwaway equipment, these systems are hard to expand later.
            Last edited by max2k; 10-09-2017, 01:55 AM.

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            • #7
              " ... with 4 car batteries ..."

              We do not recommend using car batteries.

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              • #8
                Originally posted by AzRoute66 View Post
                I doubt that one panel will put out enough voltage to charge at 48V.
                A Panasonic HIT 96 Cell 300 Watt PV Panel has ...
                Vmp = 57 Volts (approx)
                Voc = 69 Volts. (approx)

                14.8 Absorb Voltage x 4 batteries in series = 59.2 Volts

                61 Volts PV needed = 59 Volt battery bank + 2 Volts overhead for Buck Inverter.

                For sure not the ideal configuration,
                the PV Panel will be operating far above its Vmp Voltage and far below its rated 300 Watts.

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                • #9
                  ok after wearing out my multi meter i have come to this conclusion. the panel isnt putting out 48 volts, not even close. its rated at 36 volts, OCV is 42 volts. cant charge a 48 volt (or more) system when the source is less. I guess ill take one battery out of the loop, connect at 36 volts and try again.
                  Thanks to those who offer real help, encouragement and solutions. But like any other forum, there are always those that think they need to get involved with nothing positive to add to the conversation.

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                  • #10
                    The numbers you are giving 36 and 42 volts are typical of a 72 cell 24 volt nominal panel. Two in series will give you proper 48 volt charging power. You can series/parallel wire your batteries for 24 volts and use an inexpensive PWM charge controller to get this thing started.
                    2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                    • #11
                      Originally posted by littleharbor View Post
                      The numbers you are giving 36 and 42 volts are typical of a 72 cell 24 volt nominal panel. Two in series will give you proper 48 volt charging power. You can series/parallel wire your batteries for 24 volts and use an inexpensive PWM charge controller to get this thing started.
                      thanks LH, thats how i have it connected now, the sun is out and hitting the panel hard, over 10 amps, checking voltage....29vdc and 8 amps...do you think the voltage is getting too high?

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                      • #12
                        Yes! You really need a charge controller. Set up properly it will go from bulk charging to Absorb mode, which holds the voltage (in your case approx. 28.8 volts) while the battery finishes absorbing amperage. Then it will transition to Float mode and maintain the voltage about 27.2 when the batteries are full.
                        2.2kw Suntech mono, Classic 200, NEW Trace SW4024

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                        • #13
                          i have a charge controller but its for a 48 volt system, doesnt do me much good when the panel is only at 36 volts...

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                          • #14
                            its working good now, the last few days. I have it hooked up to 24VDC, so the real voltage it around 25-26 volts. I have a few 12 volt, LED lights in my house that I am powering at night. I just bought a few more at princess auto on sale, so off to home depot to get some lamp wire to add lights to the bathroom and bedroom. I may try to put my 2kw inverter into play to power up my TV or fridge.

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