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53V after 22 miles with 52V battery, is that good? Please check my math...

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    #1

    53V after 22 miles with 52V battery, is that good? Please check my math...

    My new 13.5ah 52V bottle battery has been charged up once, on Tuesday, to 100% right after I received it. I rode around the neighborhood last night for the first time a couple of miles, then rode about 5 miles this afternoon, and then did 15 miles this evening along with 75 extra pounds of kid+tagalong bike behind me. At the end of the ride this evening my DPC-14 color display is showing 53.0 volts after a total of 22 miles ridden.

    That seems pretty good to me. If we use 3.0V per cell as the LVC, times 14 is 42 volts. The battery showed 58.4 volts on the charger after the charger stopped charging. 58.4 - 42 is 16.4, 20% of that is 3.28, so 20% of the battery remaining should be 45.3 volts. At 53 volts I should have 67% battery remaining. Is my math right?
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    #2
    No, you can't work out a lithium battery's remaining capacity from voltage alone. It has a very flat discharge curve. http://batteryuniversity.com/learn/a...tate_of_charge

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      #3
      You are doing very good. Probably driving under 18 mph. And not accelerating fast. You get down to 15 miles and you are driving fast and accelerating hard.

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        #4
        I was using the throttle to get going, then using PAS 1 or 2 (out of 5) most of the time, and pedaling with no PAS on downhill sections.

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        • Gr8fun
          #4.1
          Gr8fun commented
          03-18-2017, 09:19 AM
          Editing a comment
          Good technique. Good range. Not room for much more significant improvement.

          I use pas to limit input on acceleration. From 0 to 5 mph is all heat in motor, no go. Saw that at 0 mph full throttle is 97% heat and 3% forward motion. Use gearing on acceleration keep cadence above 50. Below that motor efficiency drops quickly. Once to speed, high gear unless accelerating (passing gear). Similar to internal combustion engine, but without noise and vibration, no clues on proper techniques.
          Get a -- batt man -- if you want to geek this thing. A cadence sensor. A motor temp. Gauge.
          Driving fast is easy. Real challenge is getting range. Drive too fast and you pedal home. Waste any time you saved by going fast.
          Last edited by Gr8fun; 03-18-2017, 09:21 AM.
        #5
        Went to the grocery store yesterday, hauling a trailer, over 8 miles total. What used to take 55-60 minutes of riding before only took 35 minutes yesterday! I'm still at 50.7 volts this morning, total 31.1 miles so far on this first charge.

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          #6
          You are doing more than exercising your thumb. What size chain ring? Which cog. Speed? I have noticed little difference when i pull trailer. Weight not as much of a handicap as speed. But using lower gears much more important.

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            #7
            This is a great test, I can't wait to see what your final distance is!

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              #8
              41 miles right now with 48.5 volts showing. I think I'll call it and throw the battery on the charger now, as I'm planning on doing the 31 mile round trip commute tomorrow.

              I've been riding primarily with PAS 1 and 2 out of 5 settings, and switching to 0 on larger downhill sections and just pedaling. I generally only use the throttle for a few seconds to help get going from a stop, usually in gear 3.

              I'm running the stock 44t Bafang chain ring currently, with a 11-28 8-speed cassette using primarily gears 3, 4, 5 and 6. Chainline on 3rd gear is terrible, so I'm planning on shifting the 7th and 8th cogs to the inside of the cassette and adjusting the RD to have 6 usable gears instead of 8. I'm planning on getting the Lekkie 42t ring later, and will re-visit chainline at that time to see if I can use more of the gears efficiently.
              Last edited by PatrickGSR94; 03-19-2017, 01:45 PM.

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                #9
                With a bunch of assumptions, you are getting 14 watt hours per mile. That is for 50 volts and 31 5 miles. Assuming your full battery was 58.8 volts. Assuming 51.5 is half capacity assiming you waited an hour before reading voltage to allow for balancing. That shut off is at 43. Since you have 50.7 volts left you are doing better. I do not have the patience nor the strength to pedal that much or go that slow. The 51.5 was on a chart i saw but can no longer find.
                As the battery drops your voltage sag will drop you out under acceleration and high speed. Never get the full use from battery due to sag. Much less is available at lower voltage. I always rechargevbefore 47.
                Get a batt man or at a minimum a watt hour gauge. I played with these numbers before i got the batt man. Reasonably accurate.

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                  #10
                  well considering with pedaling I was averaging about 9 mph with this bike, and on my road bike I can only average 12-13 mph usually, my 14.5+ average on this bike is pretty good. I still like to get a workout when riding, since this is pretty much the only exercise I get. I've been riding around 3,500 miles a year on non-powered bikes the past 4 years or so, mostly commuting. My goal is to add to that total with this bike, not replace any of the road bike riding I was doing before.

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                    #11
                    I put on over 5000 last year. The uses have only increased. Next is camping trailer with solar roof..... The amount of wind in your face is directly proportional to the pleasure received....
                    • Likes 1

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                      #12
                      First commute to work this AM, I used mostly PAS 2, with some 1 and 0 on downhill sections, and PAS 3 on uphill sections. I started out at 5:22 this morning, 15.5 miles in 59 minutes to arrive at work at 6:21 AM. I think I stopped and put a foot down on the ground just 2 times the whole way. 16 MPH average, and I still have 55.1 volts! And that was with a 10 MPH headwind. That will leave MORE than enough to get home this afternoon, with a 15+ MPH tail wind.

                      Last night was only the 2nd time to charge the battery. My plan is to charge to 100% another 2 or 3 times, then switch to 80%. I'm still charging on the 3 amp setting (5 is max on the Advanced Charger). So this makes me feel pretty good about being able to do a full 31 miles round trip commute at a decent speed, even when starting out with 80% battery level.

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                        #13
                        And after getting home today, 33.5 total miles for the day (including lunch errand), averaged 18.5 MPH this afternoon! 16 miles in only 52 minutes. Still have 51.5 volts remaining.

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                          #14
                          Soon you will be taking a charger to work so you can use a full battery each way....
                          • Likes 1

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                            #15
                            Yikes, I don't want to think about how fast that would wear out the battery... a year maybe?

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