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  • batteries in series capacity

    Hi, I have a solar set up I'm planning and the particular set up I have in mind requires me to use a 24 volt battery bank.

    My question is, if I have 2 125ah 12v batteries in series, is one batteries being wasted just to add 12 volts or is the effective capacity the same as two batteries?
    In other words if one battery produces 1500 watt/hours of power does 2 batteries in series produce 1500 or 3000?

  • #2
    If one battery has 12 V * 125 Ah = 1500 Wh of storage, then two in series have 24 V * 125 Ah = 3000 Wh.

    You didn't ask, but two in parallel would have 12 V * 250 Ah = 3000 Wh.
    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

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    • #3
      Originally posted by sensij View Post
      If one battery has 12 V * 125 Ah = 1500 Wh of storage, then two in series have 24 V * 125 Ah = 3000 Wh.

      You didn't ask, but two in parallel would have 12 V * 250 Ah = 3000 Wh.
      And if you keep them electrically separate and drain one of them at 12V and then replace it with the other, you again get 1500W + 1500W.
      It is one simple example of the principle the physicists call conservation of energy.
      SunnyBoy 3000 US, 18 BP Solar 175B panels.

      Comment


      • #4
        Power and energy always adds.
        MSEE, PE

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        • #5
          Originally posted by inetdog View Post
          And if you keep them electrically separate and drain one of them at 12V and then replace it with the other, you again get 1500W + 1500W.
          It is one simple example of the principle the physicists call conservation of energy.
          Most excellent answer. I feel like I am back in the lecture hall, a long long time ago and far away.

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          • #6
            To add my 2 cents, batteries in series have the big advantage of being easier to test. While putting a significant level of current through them (either charge or draw) measure each individual battery's voltage and see how uniform they are. Good sets of batteries will be very uniform, bad ones will show up as being different from the rest. When batteries are all in parallel, they have the same voltage and it is hard to tell which ones are going bad.
            BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

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            • #7
              Originally posted by solarix View Post
              ... When batteries are all in parallel, they have the same voltage and it is hard to tell which ones are going bad.
              Which is where the DC clamp on ammeter is invaluable. They can be had for as little as $50.
              SunnyBoy 3000 US, 18 BP Solar 175B panels.

              Comment


              • #8
                Originally posted by inetdog View Post
                Which is where the DC clamp on ammeter is invaluable. They can be had for as little as $50.
                I have yet to see one under $120.00
                NABCEP certified Technical Sales Professional

                [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                Comment


                • #9
                  Originally posted by Naptown View Post
                  I have yet to see one under $120.00
                  Sears $ 59.99

                  http://www.sears.com/craftsman-digit...&mktRedirect=y

                  E-Bay $ 34.88 Free shipping

                  http://www.ebay.com/itm/UNI-T-UT203-...-/231461950893

                  If you have a generator, it's nice to have one that also measures frequency so you can adjust the rpm.

                  Comment


                  • #10
                    Originally posted by Naptown View Post
                    I have yet to see one under $120.00
                    Check out http://www.sears.com/craftsman-digit...1&blockType=G1. I have one and it works great. The thermocouple range and probe is a nice added feature.
                    It is $60 now, but used to be as low as $50. Be careful not to get the $40 model which is sometimes listed as AC/DC because of the volts only and does not have a DC amp range.
                    If you want the fancier Craftsman branded model, http://www.sears.com/craftsman-profe...p-03473756000P, you can pay $110.
                    Last edited by inetdog; 06-24-2015, 12:33 PM.
                    SunnyBoy 3000 US, 18 BP Solar 175B panels.

                    Comment


                    • #11
                      Good find
                      Thanks
                      Would also be good tool for HVAC and solar thermal.
                      Anyone know what the thermistor is 10K?
                      NABCEP certified Technical Sales Professional

                      [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                      [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                      [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                      Comment


                      • #12
                        Originally posted by Naptown View Post
                        Good find
                        Thanks
                        Would also be good tool for HVAC and solar thermal.
                        Anyone know what the thermistor is 10K?
                        It is actually a K type thermocouple, not a thermistor. If want to extend the leads you need to use thermocouple wire. The sensitivity and absolute accuracy in the range around room temperature is not great, so I would not recommend it for most HVAC work except in a comparative-only application (or if you calibrate it each time you use it.)
                        SunnyBoy 3000 US, 18 BP Solar 175B panels.

                        Comment


                        • #13
                          Originally posted by Willy T View Post
                          Sears $ 59.99

                          http://www.sears.com/craftsman-digit...&mktRedirect=y

                          E-Bay $ 34.88 Free shipping

                          http://www.ebay.com/itm/UNI-T-UT203-...-/231461950893

                          If you have a generator, it's nice to have one that also measures frequency so you can adjust the rpm.
                          I have that UT203 clamp on and it seems to provide me pretty accurate readings when I compare it to the Fluke 902 clamp on at work, although the Fluke meter can do much more than the UT203.

                          Comment


                          • #14
                            No reason to buy a uni-tasker, just buy 1 meter that does it all.

                            Greenlee CM-950 for $85

                            Extech MA435T for $103

                            Klein CL2000 for $139

                            No reason to buy crap from Flea Bay.
                            MSEE, PE

                            Comment


                            • #15
                              lol, crap from flea bay.

                              Then get it from Amazon.

                              http://www.amazon.com/Digital-Clamp-.../dp/B005HOPRRK

                              Originally posted by Sunking View Post
                              Klein Tools CL 2000 for $110
                              The Kline Tools meter listed below is AC amps only. It says CL 2000 but the link is not for that meter.

                              CL 1200

                              Key Features:

                              Auto-ranging clamp meter measures AC/DC voltage, AC current, resistance, capacitance, frequency and duty cycle.
                              Also tests non-contact voltage, diodes, and continuity.
                              Backlit display and work light.
                              Built-in magnetic mount for hands-free convenience.
                              Non-contact voltage tester.
                              Quick response analog bar graph shows elusive flucutations.
                              Built-in lead storage protects leads.
                              Includes case, test leads and batteries.
                              CAT IV safety rating.
                              Height: 7.65 in.
                              Weight: 1 lb
                              Width: 2.56 in. (65 mm)
                              Batteries: 2 x AAA
                              Jaw Size: 1.25 in. (32 mm)
                              Ingress Protection: IP42
                              Drop Protection: 2 m / 6 ft.
                              Safety Rating: CAT IV 600V

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