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How do I use this watt meter?

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    #16
    Watch Watt Hours used during a ride. That's your 'gas gauge'.

    You have a 20 Ah battery, 48V right? 48V*20 Ah=960 Wh capacity, under ideal conditions. When it says you have used 960 Wh, you will be empty. Since we ride in less than ideal conditions and don't get ideal capacity, we need to be a little conservative when estimating available energy vs specifications.

    Ah count would be 20, same idea, but less precise.

    You can also watch pack voltage. When it starts getting almost as low as your LVC (Low Voltage Cutoff setting) you know you are about empty, as the controller and BMS will both refuse to let you over-discharge the pack. This LVC will happen first at high power, so you might be able to eek out a bit more range at low power, but not much.

    Eventually you will learn how much Wh capacity you can safely count on with your bike and riding conditions. This will gradually reduce as the pack ages.
    Last edited by JPLabs; 04-09-2016, 10:22 PM.
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    • Grover
      Grover commented
      Editing a comment
      Hey JPLabs - So just let me make sure I'm getting this...

      I have a new 48V x 21 Q pack. That should give me +/-1008 AH when fully charged.
      Before I ride - I reset the batt-man. The ah reading will show as 0
      Then as I ride it will read ah used.
      1000 ah is my shut off limit- so I need to be home before it gets there

      Have I got that correct?

      also how do I know what my LVC is on that pack?

      cheers
      Last edited by Grover; 05-14-2016, 10:29 AM.

    • JPLabs
      JPLabs commented
      Editing a comment
      It's right, yes. Except you won't quite get the rated 1008 Wh capacity, because you can't pull the pack all the way down to it's Low Voltage Cuttoff (LVC), due to voltage sag. The more current you are pulling, the lower the pack voltage sags, so the LVC activates a few volts early.

      Both the Pack's BMS and the controller have a LVC. The controller is programmable and comes with a 42V cutoff for a 52V pack, as I recall. Don't know about the BMS, but it will be near that level.

      It would be good to baseline your pack sometime. Run to LVC. Then see how many Wh you used. That becomes your target.

    • Grover
      Grover commented
      Editing a comment
      cheers JP - Im still having battery woes - Im gonna post seperately

    #17
    So Wh on the gauge now is purposely at 0, because the pack is fully charged and I haven't riden it, correct?
    You're saying if I kept this gauge on, then rode the bike until the battery was half dead, I'd see Wh = something around 480 Wh?

    ​Regarding voltage, does 54.75 seem right for this 48v battery, having only used it for ~10 cycles?
    What is my LVC - how do I see what that is?

    Thanks~.

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    • JPLabs
      JPLabs commented
      Editing a comment
      Yes, that's right. The gauge doesn't know how much energy is in the battery, only how much you have used. Recharge fully, reset gauge to zero, when it shows 480 you are about 1/2 empty.

    • lukehmail
      lukehmail commented
      Editing a comment
      Thanks JPlabs.

    #18
    OK, I just bought a DCP-14 color display (thanks Eric for the loyalty discount). I was going to get a battman, but I feel for my daily commute, using the battery voltage gauge and the watt-hours will get me pretty much everything I need. I like the large display, and having a batt-gauge that works for my 52v pack is a big plus. I found that my watt-meter from Luna (of which I burnt out two (I don't recommend using on 52v packs btw) was nearly impossible to safely read while riding (especially at 30mph, more power, hahaha!).

    I look forward to riding with the new display and I think I will prefer the portrait orientation more than my older display.

    One thing that I did not check out and would love an answer to is: Will this effect my custom programming of the controller? I have my PAS 0 at 100% throttle and have adjusted the amperage to 30. Will my settings keep or is there a way to re-program these nice controller settings through the new display?

    Thanks for the help.

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      #19
      Alpinist how will the voltage gauge and the watt-hours the motor is putting out help you (what the display shows)? Trying to wrap my head around this. Sounds like it doesn't take into account the battery, so still unclear on what info you expect to see there and how you'll translate that into remaining power left in your battery.

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        #20
        Alpinist, no it will not change your custom programming of the controller and there is no way to reprogram the controller through the color display. It is just like the old displays, just a few more key features such as voltage display.

        Luke you need to make sure you have the wat meter hooked up with Both xt90s of the wattmeter ..it sounds like you just have it connected to just one. When you unplug the wattmeter it resets your amp hour and watt hour readings to zero....so then you ride with it connected and it will measure all the juice which flows between your battery and controller (amp hours or watt hours)

        read my story by googling "ebike battery math" for more explanation.

        The color display will tell you your voltage which will give you a good idea of when your battery will die ..but will not tell you how many amp hours your battery is putting out. (or watt hours).

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