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Exaggerated charge rate

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  • Exaggerated charge rate

    BatteryMon is showing correct discharge rate (i.e. 13000 mW) but charging rate is showing impossible values, for example 950000 mW.

    The power supply is only able to give 2.64 A at 19 volts, which gives a maximum of 50000 mW.

    Is this a bug or is this a compatibility problem. My computer and batteries are brand new and are working fine. Batteries give all the power they're supposed to.

    Thanks for your help.


  • #2
    BatteryMon has two different methods of figuring out the charge/discharge rate. The first method is to query the battery itself as some batteries will report what their charge rate is. If the battery does not report this information then BatteryMon falls back to its second method, which is to estimate the charge rate based on data it has collected.

    What you’re likely seeing is BatteryMon using the second method but with very limited data causing the estimates to be incorrect. To fix this simply leave BatteryMon running a while longer so that it can get more samples and calculate a more accurate charge rate.


    • #3
      I don't know exactly what you really mean by "a while longer", but it has been running for several charge/discharge cycles and the charge rate has not changed a bit.

      But your theory was very plausible. Would you have a 3rd theory, just in case?

      Last edited by carbo; 04-10-2007, 09:58 PM.


      • #4
        The estimate should somewhat level out after a few minutes running and about a dozen samples so in your case it should have been running plenty long enough. BatteryMon updates its estimate with every sample, so the fact that the charge rate has not changed at all leads me to believe that BatteryMon is using the first method I mentioned and acquiring its data straight from the battery.

        You can check whether this is the case by going into the battery information page and looking at the charge rate field (this should be at the bottom). If there is a value listed here then the battery itself is reporting the charge rate. Why the battery itself would report an impossibly high charge rate I wouldn’t know.

        If the batteries charge rate is listed as “N/A” in the battery information page then BatteryMon is using an estimate and I’m not sure why it is giving you an incorrect charge rate, especially if it calculates the discharge rate correctly.


        • #5
          According to your explanation, it would mean that the charge rate is really coming from the battery itself, since there's a value at the charge rate reported in the battery information page, and which is exactly the same high value as I reported before.

          I would say that the same theory would apply to the charge rate reported by the battery as well as a value that would be estimated. As you said, why would it be incorrect in 1 direction and not in the other. I also noted a negative value in the battery information page when it is drawing power from the battery which is perfectly logical if it reads a value on a resistor in series with the load. Then why shouldn't it be on a different scale when charging the battery, the current is only reversed.

          By the way, my computer is a tablet PC LE1600 from Motion Computing, just in case where it would light up the situation.

          Thank you very much for your efforts to solve the problem.
          Last edited by carbo; 04-12-2007, 03:20 AM.


          • #6
            Unfortunately at this stage there is nothing that we can do. BatteryMon is simply reporting the numbers given to it by the Battery and the charging circuitry.

            I had a quick look on the net for your computer but I could only find fairly general data about your batteries. To find out why the battery is reporting these figures you would have to contact the manufacturer. At a guess I would say that because it is so rare for anyone to try and get the charge rate information out of the battery this functionality was not tested properly by the manufacturer and simply has a bug in it.


            • #7
              I agree with you about that, this is the only logical explanation. In fact, I was looking for software like BatteryMon mainly because computers come with a battery tool that says fairly nothing but the actual charge and the remaining time. I wanted a tool to know how much time I ran on a particular battery. Following batteries degradation over a period of time.

              An improvement would be a timer for total discharging time, only running time on battery. It would be also interesting to include voltage and discharging rate in the log.

              I will start a new topic on another problem I have with a Compaq Presario 1200. No battery wants to charge anymore on it. In fact it seems to discharge the batteries.

              Thanks Michael.


              • #8
                Originally posted by carbo View Post
                BatteryMon is showing correct discharge rate (i.e. 13000 mW) but charging rate is showing impossible values, for example 950000 mW.
                At the light of BatteryMon 2.1 new log, I've been able to see some patterns in the charge rate and to make some calculations. At first I thought that charge rates were only scaled to high, like is 60 times.

                Using the new log, I quickly realized that using a ratio of 60, would mean that the charge rate stays around 16000 mW during all charge time until it reaches 100%. In a log from a complete discharge/charge cycle, I noticed that Life % is proportional to time when discharge rates are steady, so since the increase of life percentage is fast going to 75% of the charge and gets slower all the way to 100%, then charge rates should do the same.

                By subtracting the lowest charge rate from the highest one, it gives me something like 23000 mW, to which I added a few mW (2000mW) to ensure a minimum charge rate when approaching 100%. So by adding this 2000 mW to the highest charge rate value, it gives me an offset value.

                At this point, it is important to say that I also noted that the highest charge rate occurs at the end of the charging cycle, so the charge rates are also in reversed order. So the actual charge rates must always be smaller than this offset value and subtracted from it in order to get positive values and also in the proper order. Using this calculation, it gives me a charge rate of about 25000 mW from 0% to 75% then it starts decreasing slowly until it reaches about 2000 mW at 100%.

                There is a question that I can't answer though, what is the correct value to add to the 23000 mW? I added 2000mW as an arbitrary value but is there a way to evaluate more precisely this minimum charge rate?

                Last edited by carbo; 05-05-2007, 06:46 PM. Reason: Value corrections