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Power Meter on 24volt Lithium

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  • Power Meter on 24volt Lithium

    The Power Meter on 24volt Lithium has a consistent drain on the battery as many know.

    Does anyone know if the electronic monitoring circuitry in the battery will "stop monitoring" if the voltage drops too low?
    http://www.cgiconnection.com/download

  • #2
    Re: Power Meter on 24volt Lithium

    Originally posted by onlycordless View Post
    The Power Meter on 24volt Lithium has a consistent drain on the battery as many know.

    Does anyone know if the electronic monitoring circuitry in the battery will "stop monitoring" if the voltage drops too low?
    Since activating the Power Meter on the battery requires pushing a button I'm not convinced the battery drain is caused by same.

    Comment


    • #3
      Re: Power Meter on 24volt Lithium

      The drain is caused by the electronic monitoring and protection circuit. Lithium Ion requires protection from overcharging or overcurrent. Either condition can lead to thermal runaway...meltdown. Additionally, it can't recover if the voltage gets too low. The circuit disconnects the battery before that can happen. In some products, designed for Lithium Ion, this circuit is contained in the device. With many of the tool manufacturer's it is in the battery. It has to be in the battery when designing retrofitting Lithium Ion to older tools...like Milwaukee did. In the case of Milwaukee, the circuit actually stores usage information that can be downloaded from the battery. Not sure if Ridgid, also made by TTI, does the same. If this info is in volatile memory, it would require power all the time to retain it.

      Perhaps in the next generation of Lithium Ion, Ridgid will design it so the circuit does not put such a large drain on the battery when not in use...better even if it has zero drain.

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      • #4
        Re: Power Meter on 24volt Lithium

        With the old Nicad batteries one could stick a meter on them at various stages of discharge to get a feel for useful range. With all the electronics in the LI batteries can we still meter them and get any kind of reasonable info?

        Comment


        • #5
          Re: Power Meter on 24volt Lithium

          Originally posted by roadrashray View Post
          With the old Nicad batteries one could stick a meter on them at various stages of discharge to get a feel for useful range. With all the electronics in the LI batteries can we still meter them and get any kind of reasonable info?
          You could...but you'd have to open them up and measure the current flow across the electronic circuit. Alternatively, you could just fully charge them and let them run down, then calculate the current based on time divided by how long it took them to become "empty." They will run very flat till they fall off the curve. If you know the Ah of the batteries you will get a very accurate measure of current bleed. Unfortunately, this will take a while....until they drain you won't know anything.

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          • #6
            Re: Power Meter on 24volt Lithium

            I hope the next gen of lithium has matured to the same level as other cells(AA,AAA, 18650,etc..) in regards to shelf life.

            Maybe, through the lifetime of the warranty, RIDGID will give us better batteries as these current batteries become obsolete over the years and we won't have to pay for the batteries. If they work in our 24 volt dinosaur tools.
            Or, maybe Eestor's promises will have us all on the high capacitors.
            http://www.cgiconnection.com/download

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            • #7
              Re: Power Meter on 24volt Lithium

              Here's another way but only if you have the required equipment. If not you'll spend far too much $$$ on it.

              1. Connect a 4-1/2 or 5-1/2 digit benchtop digital Voltmeter across the battery and about every hour log the Voltage. You want to be able to read changes of 0.01 Volt and that's where the common 3-1/2 digit meter just won't do.

              2. Connect up a variable Voltage (0-50 Volts) DC power supply in series with a diode (to prevent reverse flow) and a 1000 ohm resister to the battery using clip leads.

              3. Using a DC Ammeter connected in series with the above, set the charging current to 5/1000 Amp and watch the Voltmeter.

              If the Voltage slowly falls, increase the charging current slightly and then watch the Voltage. If the Voltage rises, lower the charging current a bit. Pretty soon you'll have a good idea of the leakage current and the current required by the monitoring circuit.

              When a power tool battery is engineered, they figure that most users will be charging, discharging and recharging the battery once a week if not more often.

              Comment


              • #8
                Re: Power Meter on 24volt Lithium

                Originally posted by Woussko View Post
                Here's another way but only if you have the required equipment. If not you'll spend far too much $$$ on it.

                1. Connect a 4-1/2 or 5-1/2 digit benchtop digital Voltmeter across the battery and about every hour log the Voltage. You want to be able to read changes of 0.01 Volt and that's where the common 3-1/2 digit meter just won't do.

                2. Connect up a variable Voltage (0-50 Volts) DC power supply in series with a diode (to prevent reverse flow) and a 1000 ohm resister to the battery using clip leads.

                3. Using a DC Ammeter connected in series with the above, set the charging current to 5/1000 Amp and watch the Voltmeter.

                If the Voltage slowly falls, increase the charging current slightly and then watch the Voltage. If the Voltage rises, lower the charging current a bit. Pretty soon you'll have a good idea of the leakage current and the current required by the monitoring circuit.

                When a power tool battery is engineered, they figure that most users will be charging, discharging and recharging the battery once a week if not more often.
                For this to work you'd have to very accurately measure the resistor and be able to measure the voltage very accurately, like you said. A small mistake on estimating how much power the resistor used would directly effect the estimate of how much the internal circuit uses.

                You would also have to assume the power draw of the monitoring circuit is the same under load as it is when idle.

                That is all moot for me because I don't think I have a voltmeter or ammeter accurate enough to instantaneously measure such small values.

                Comment

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