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  • #31
    Originally posted by bcroe View Post
    OK for just riding through occasional power glitches, the 2.27V float should cover it. For
    equipment needing a quicker recovery, the charger should start at 2.45V and then drop
    down to 2.27V when current drops to .01C.
    That is not how a Float Charger works. A Float Charger is a constant voltage, current limit device. The current limit can be as high or low as you want within tolerance of the battery charge acceptance. Grabbing numbers out of the sky lets say you have a 10 volt 10 AH battery, and a 10 volt 1 amp float charger. So let's say the battery is completely discharged and you connect the charger. For about 10 hours the charger will supply 1 amp until th ebattery terminal voltage reaches 10 volts. At that point the current twill taper off toward zero amps after another couple of hours of a saturating charge, aka Absorb. The charger will hold the battery at 10 volts supplying only enough current to over come the self discharge current of the battery.

    This is the basic operation of any Stand-By Battery service which is exactly what, UPS, utilities, and telephone companies use on their battery plants. It is the kindest most gentle charger there is and provides the maximum battery life. It only has one disadvantage of being slow to recharge. A 3-stage from dead to full is around 16 hours with a C/10 charge current. Float with C/10 will be around 20 to 24 hours.

    Note Telcos, utilities, and UPS use much higher charge currents in excess of 1C. But they do not use the same kind of batteries you do.
    MSEE, PE

    Comment


    • #32
      Originally posted by bcroe View Post
      OK for just riding through occasional power glitches, the 2.27V float should cover it. For
      equipment needing a quicker recovery, the charger should start at 2.45V and then drop
      down to 2.27V when current drops to .01C.
      That will cover it more or less. However, depending on the age of your cell, you may never reach .01C in absorb, so it may be wise the first time out to merely watch for no significant change in current during a 3 hours period once into the absorb stage. You don't want to hold it at the absorb voltage longer than necessary. That would accurately define your REAL absorb current to then switch to float. Then just hold it there in float for 12 hours or so.

      If I set the voltage, the battery will set the current. If I limit the current, the battery will control the voltage.
      You want Constant Voltage charging, where you set the upper voltage limit in the charger, and merely let the charger provide as much current as it is capable of - within reason. You could run a 1A charger, or a 25a charger - makes no difference to a Cyclon, other than getting to absorb really faster and shortening overall charge time. You DONT want to run constant-current and let the voltage rise very high - Enersys warns against this unless you have no choice and are under very tightly controlled circumstances.

      Occasionally you'll see references to CC/CV, which the "CC" part is just that initially during bulk, your charger is putting out as much current as it can constantly, and once the CV point is reached, then the charger merely puts a hold on the upper voltage limit, and now the battery will absorb what it can with that voltage limitation and current drops away which is a natural reaction of the battery doing the actual current control, and not the charger. The ONLY thing it is doing is limiting voltage at this point.

      What level of current might occur after discharging a 25AH cell?
      As much as your charger has available while in the bulk stage. I wouldn't use anything larger than a 25A charger on your 25ah cell, so you don't exceed 1C, but they are capable of taking much more. If you have the time and no need to recharge in 30 minutes basically, you can use lower amperage chargers. Just make sure they have an upper voltage limitation of 2.45v for cyclic charging, or 2.27 for long term standby charging.

      Load current will be low, so can the level of discharge be estimated from V? What is a good low cutoff V?
      It all depends on Mr. Peukert, but for general purposes I'd suggest not going below 2.0V.

      You can get much more detailed charging procedures from the application manual link at the bottom of this page:
      http://www.enersys.com/Cyclon_Batteries.aspx

      Quick note about what Enersys defines as the difference between cyclic and standby use:

      If you don't have two successive charges within 30 days, AND those two successive charges are not less than 14 days in between, then you are in a standby environment. In this case, just using a simple 2.27v CV charge would be fine. Otherwise, use the 2.45v until finishing absorb, and then the 2.27v float for many hours.

      Real world - since I'm not a commercial site with mega-millions tied up in batteries, I'll just charge up to 2.45v, finish absorb, and float for a few hours no matter what, and accept the loss of cycles that may result. With my usage, I'll probably never see the difference, and the battery will just calendar-age faster than any non-perfect charging setup would degrade cycle life.

      Solar is a different story - I just set BOTH my absorb and float to the same value, in this case 2.45v per cell, and call it a day and just get in as much as I can, since there is no luxury of long floats during the day.

      Comment


      • #33
        Charging Goals

        Originally posted by PNjunction
        You want Constant Voltage charging, where you set the upper voltage limit in the charger

        You DONT want to run constant-current and let the voltage rise very high

        As much as your charger has available while in the bulk stage. I wouldn't use
        anything larger than a 25A charger on your 25ah cell, so you don't exceed 1C

        I'd suggest not going below 2.0V.

        You can get much more detailed charging procedures from the application
        manual link at the bottom of this page:
        http://www.enersys.com/Cyclon_Batteries.aspx

        Quick note about what Enersys defines as the difference between cyclic and standby use:
        This should be enough info to design chargers for several appliances here, or check
        that the one it came with is adequate, thanks. I want to just plug stuff in indefinitely
        and not worry about the treatment of the battery.

        I note a portable audio amp here has a nice charging indicator. A red LED flashes very
        rapidly so as to appear constant at the beginning. Then it tappers off to slower and slower
        flashing, finally stopping. I wonder if its tied to decreasing charge current? Bruce Roe

        Comment


        • #34
          By far the simplest would be the taper charger, that is nothing more than a full wave rectifier, a smoothing cap on the output, and set for around 2.27v. Just don't exceed C/50 charge current. That would appear to be something you could just set and forget for the most part if your needs aren't critical.

          Comment


          • #35
            Originally posted by Sunking View Post
            How much voltage do you need?
            12 Volt,,, LED night-light

            Originally posted by Sunking View Post
            As I said before the Cyclon line is a great battery, but not really intended for cycle service.
            Thank you for the input.

            Based on Cyclon's questionable cycling capability, and high cost,
            I've scrapped the idea of designing a post lamp with the battery and controller hidden & secure "in" the post.
            [CENTER]SunLight @ Night[/CENTER]

            Comment


            • #36
              Originally posted by Shockah View Post
              12 Volt,,, LED night-light



              Thank you for the input.

              Based on Cyclon's questionable cycling capability, and high cost,
              I've scrapped the idea of designing a post lamp with the battery and controller hidden & secure "in" the post.
              Have you thought about LiPo or cylindrical LFP?

              You can get 3S or 4S LiPo up to 6 AH and the package should fit in a pole. Think of RC plane batteries. Here is an example.

              MSEE, PE

              Comment

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