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  • #31
    Originally posted by Sunking View Post
    OK something is wrong with this picture.

    Bulk is a constant Current Mode, not Constant Voltage as you describe. There is no specified voltage during Bulk charge other than a Set Point to terminate the the Bulk stage at which point switches to Absorb. For example if Bulk is set to 14.1 volts on a 30 amp charger with a discharged battery what you would expect to see is the full 30 amps. Initially the voltage will be well below 14.1 volts, down in the 12 to 13 volt range with a steady 30 amps. As the battery charges, the voltage begins to rise but still 30 amps. Once the battery voltage reaches set point of say 14.1 volts, the charger switches to Absorb which is a Constant Voltage, current Taper.
    I agree with your statements. How would I be able to run a better test? Because this was my first time, I could have made a series of erros, although what I really think is happening here, is that the IOTA is not really a full 4 stage charger.

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    • #32
      Originally posted by mschulz View Post
      I agree with your statements. How would I be able to run a better test? Because this was my first time, I could have made a series of erros, although what I really think is happening here, is that the IOTA is not really a full 4 stage charger.
      Its not, it is a CONSTANT VOLTAGE charger. They are just jacking the set point voltage to make it behave like a multi-stage charger.

      Don't take that wrong, because there is nothing wrong with a Constant Voltage charger. In fact Float Chargers are the best to use, the just are not as fast, but very kind to the battery. Every utility out there with battery plants use Float Charger only.

      What I would do if I were in your shoes is first look at the battery manufacture spec to see if they publish Absorb Voltage. Should say something like 2.35 to 2.45 volts per cell (2.4 is a good default) or say 14.1 to 14.7 volts (14.4 would be good in this example for a 12 volt battery.

      OK assuming the battery is discharge if you were to set the Iota to 14.4 volts open circuit voltage, what you should observe is initially the battery will take full current of or near 30 amps, and if you look at the voltage will be less than 14.4 volts. Once the battery voltage reaches 14.4 volts, the current will taper off and continue to do so until the battery is saturated. [B]WARNING[/B], without intervention on your part can damage the battery if you let it go to long. An automatic system will terminate Absorb when the current tapers of to 3 to 5% of C where C = battery AH capacity. So if that is say a 300 AH battery you want to pull the plug when current tapers off to 9 to 15 amps, or lower the voltage to FLOAT VOLTAGE of around 13.2 to 13.6 depending on battery spec.
      MSEE, PE

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      • #33
        Originally posted by Sunking View Post
        Its not, it is a CONSTANT VOLTAGE charger. They are just jacking the set point voltage to make it behave like a multi-stage charger.

        Don't take that wrong, because there is nothing wrong with a Constant Voltage charger. In fact Float Chargers are the best to use, the just are not as fast, but very kind to the battery. Every utility out there with battery plants use Float Charger only.

        What I would do if I were in your shoes is first look at the battery manufacture spec to see if they publish Absorb Voltage. Should say something like 2.35 to 2.45 volts per cell (2.4 is a good default) or say 14.1 to 14.7 volts (14.4 would be good in this example for a 12 volt battery.

        OK assuming the battery is discharge if you were to set the Iota to 14.4 volts open circuit voltage, what you should observe is initially the battery will take full current of or near 30 amps, and if you look at the voltage will be less than 14.4 volts. Once the battery voltage reaches 14.4 volts, the current will taper off and continue to do so until the battery is saturated. [B]WARNING[/B], without intervention on your part can damage the battery if you let it go to long. An automatic system will terminate Absorb when the current tapers of to 3 to 5% of C where C = battery AH capacity. So if that is say a 300 AH battery you want to pull the plug when current tapers off to 9 to 15 amps, or lower the voltage to FLOAT VOLTAGE of around 13.2 to 13.6 depending on battery spec.
        Thanks Sunking, as always great to have your advice here to keep me on track.

        The battery I will be using is the Trojan 31AGM and my data sheet says Absorb should be 14.1-14.7 and float at 13.5. With the built in IQ4 my Dual Voltage jack (jumper) is disabled so my unit can not be adjusted manually. What it does say is: "Models with an internal IQ4 smart-charger (not sure how smart) give the user the benefit of automatic Bulk, Absorption, and Float stage charging. This increases the chargin capacity of the IOTA charger, decreases charge time and insures proper and safe battery charging without over-charging." It then just talks about what is happening when the LED blinks and where it is in the charge.

        Would it be possible that the battery I was using, due to age and abuse, could not actually attain float status? I am going to assume that by the numbers, this is safe to hook up to my new battery - not in service?

        In regards to this Trojan 31AGM, can I charge it at c/4 or should I be around C/8 when on PV Panels?

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        • #34
          Originally posted by mschulz View Post
          In regards to this Trojan 31AGM, can I charge it at c/4 or should I be around C/8 when on PV Panels?
          I should have caught this earlier, I did not realize you had a T AGM. Things are not near as complicated. You don't need no stinking stages, just a simple Constant Voltage charger like your Iota. Only question is what voltage to pick. Well that depends on the application of Float Service where the battery is only used in emergencies so that is out for you I believe.

          That leaves us cycle service, but what kind of charge source. Let's say the battery is used in a golf cart daily and recharged every night on a commercial charger. Trojan calls this Daily Charge charged from a hard source of the utility. If you look on page 14 that is between 13.8 to 14.4 volts. Charge is complete when current tapers to C/200 so on a AGM-31 that is .5 amps. This is the range for your [B]Iota[/B].

          For RE applications things change. They raise the voltages because solar is a soft source. Range now becomes 14.1 to 14.7

          So if I were you set your Iota on 14.4 volts on your new AGM and let it go until you see charge current falls just below 1 amp, then terminate charge, or lower voltage down to 13.5 Float Voltage. Then cycle the battery down to 50%, recharge, and repeat cycle a few times to form the plates as recommended by Trojan.

          When on Solar set your controller for 14.7
          MSEE, PE

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          • #35
            Originally posted by Sunking View Post
            Then cycle the battery down to 50%, recharge, and repeat cycle a few times to form the plates as recommended by Trojan.
            I didn't see that in the 24 page Trojan user guide. Don't get me wrong, I trust your judgement and expertise, I just want to double check.

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            • #36
              Originally posted by mschulz View Post
              I didn't see that in the 24 page Trojan user guide. Don't get me wrong, I trust your judgement and expertise, I just want to double check.
              My bad typo error of fat thumb. manual here. Go to page 14.
              MSEE, PE

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              • #37
                Originally posted by Sunking View Post
                My bad typo error of fat thumb. manual here. Go to page 14.
                Thanks Sunking, That is the one I have.

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                • #38
                  For AGM batteries you don't really need any fancy charging algorithm, just a good single stage float charger with enough capacity for the battery to charge at at least C/10, can go as high as C/4. So with a solar system or daily cycle use, charge at maximum manufacture spec if you have temperature compensation, otherwise go to the middle ground like 14.4 on a range of 14.1 to 14.7. Now if you float use float voltage.

                  Hope that helps.
                  MSEE, PE

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                  • #39
                    This questions is for the professionals out there:

                    In your professional opinion, when running an AGM battery, I am throwing money away when buying a MPPT Solar Charge controller that does not allow me to specifically adjust my Float, Absorb, and Bulk voltages. What I mean is comparing a analog Morningstar to like a KID or Classic 150. It seems by the time I get all the gizmos, the morningstar and Midnight Classic runs about the same $$. For further clarification, I am not concerned about the cost, as I will pay more for "set it and forget it".

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                    • #40
                      Originally posted by mschulz View Post
                      This questions is for the professionals out there:

                      In your professional opinion, when running an AGM battery, I am throwing money away when buying a MPPT Solar Charge controller that does not allow me to specifically adjust my Float, Absorb, and Bulk voltages. What I mean is comparing a analog Morningstar to like a KID or Classic 150. It seems by the time I get all the gizmos, the morningstar and Midnight Classic runs about the same $$. For further clarification, I am not concerned about the cost, as I will pay more for "set it and forget it".
                      Hold the buss, MPPT is far superior to PWM. At a minimum using a PWM controller you will loose 32% of your panel wattage turning your 100 watt panel into a 67 watt panel. A MPPT only looses 2 to 5%.

                      It takes a 300 watt PWM system to equal a 200 wat MPPT system. A 300 watt PWM system will cost you around $600 to $700. A 200 watt MPPT system will cost you around $400 to $500 for the exact same amount of power.
                      MSEE, PE

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                      • #41
                        Originally posted by Sunking View Post
                        Hold the buss, MPPT is far superior to PWM. At a minimum using a PWM controller you will loose 32% of your panel wattage turning your 100 watt panel into a 67 watt panel. A MPPT only looses 2 to 5%.

                        It takes a 300 watt PWM system to equal a 200 wat MPPT system. A 300 watt PWM system will cost you around $600 to $700. A 200 watt MPPT system will cost you around $400 to $500 for the exact same amount of power.
                        Sorry Sunking, should have specified that I was comparing a Morningstar TriStar MPPT vs KID/Classic where I can set the exact voltage. Even with out the cost, PWM will not meet my needs. The morningstar seems to be dip switches that control set charge voltage where as Midnite solar gives me the opportunity to set the voltage manually.

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                        • #42
                          Originally posted by mschulz View Post
                          Sorry Sunking, should have specified that I was comparing a Morningstar TriStar MPPT vs KID/Classic where I can set the exact voltage. Even with out the cost, PWM will not meet my needs. The morningstar seems to be dip switches that control set charge voltage where as Midnite solar gives me the opportunity to set the voltage manually.
                          Just make sure the dip switch settings are within range of your battery specs. If not, the TS-MPPT can be set via a serial port or RS-232 for anything you want (within limits). That's what I did to charge my NiFe bank.

                          Having both TS-MPPT and Classic, I think the TS-MPPT has an edge in efficiency at less than full noon sun, and no fans. But the Classic has remote controlability.
                          (and the TS-MPPT does not come with the optional meter panel display. ~ $100)


                          Powerfab top of pole PV mount | 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 ||
                          10 Evergreen 205w on Powerfab top of pole PV mount | Midnight Classic 200 |
                          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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