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  • Battery Charge Time solar powered bike

    I am a student in a Mechanical Engineering Technology program. As my groups senior project we are trying to make a solar powered bike/trike. I am looking for suggestions and some info on batteries. As of now we are looking at the standard E bike battery packs similar to golf cart batteries. They are usually 36v or 48v usually between 10ah and 20 ah. I am trying to figure out how to determine the charge time using a solar panel with the below specs. I am still researching at this point. Any other comment or suggestions in any part of the project would be greatly appreciated.

    Pnom - 345 W
    Power tolerance +5/-0%
    Average panel efficiency - 21.5 %
    Rated Voltage - 57.3V
    Rated Current - 6.02 A

    Thanks!!!!

  • #2
    Golf Cart batteries are on the order of 200 to 225 AH.
    MSEE, PE

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    • #3
      Originally posted by sdelgad8 View Post
      Pnom - 345 W
      Power tolerance +5/-0%
      Average panel efficiency - 21.5 %
      Rated Voltage - 57.3V
      Rated Current - 6.02 A

      Thanks!!!!
      Well I am not going to give you the answers, but the tools to figure it out. It is really simple.

      H = AH/A
      A = AH/H
      AH = A * H

      H = Time in hours
      A = Amps in current

      Nothing more to it than that well except charge efficiency of the battery chemistry you use. Then we can throw C in the equation where C is the correction Factor.

      What kind of battery and at what rate can they be charged up at. For example a 10 AH battery charged at the 5 hour rate is 2 amps. You cannot exceed the manufactures maximum charge rate.

      FWIW forget panel efficiency and tolerance, it has no meaning and useless information. Everything depends on how you intend to regulate voltage and current, and what battery chemistry you use.
      MSEE, PE

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      • #4
        That helps I am researching different batteries at the moment trying to see what the best option but this is what one company uses in their electric charge e-bikes. They may not be golf cart batteries but what from I am reading they are similar. I am going to assume that with a 4 to 6 hour charge their maximum charge rate is approx 2.5 amps.


        I am slowly putting pieces together.
        Thanks again for the response!


        36 Volt 15 Amp Hour USA Made Lithium Ion E Bike Battery

        Weight: 7.2 Pounds
        Dimensions: L 8" x W 6" x H 3.75"
        Range: From 20 - 40 Miles per charge (Riders Weight, Input, Bike, and Terrain
        Contingent)
        Warranted: 2 year Manufacturer's Warranty
        Cycle Life: 1800 Charge and Discharge Cycles
        Assembly: No assembly required - Plug and Ride
        Charging Time: 4 hrs - 6 hrs. Charger Included with Kit purchase.


        -Saul D.

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        • #5
          Saul the most important thing with any Electric Vehicle is the battery Energy Density expressed in Wh/Kg. As you can understand weight is crucial so the higher density the better. Lead Acid batteries that golf carts use is on the order of 30 to 40 Wh/Kg. They also have some other nasty characteristics not favorable for EV as they do not like to be discharged deeply. You can only take them down to about 50% so you have to leave the tank half full so to speak. So lead acid chemistry is not what you are looking for. If you use lead acid expect very short ranges, big, and heavy. Not something you want.

          NiCd and NiMh are also out as they have even lower energy density but they can be completely discharged and discharged at very high rates.

          By now you should have already figured out Lithium is what you want as th eenergy density comes in at 90 to 200 wh/Kg. Some can be charged and discharged at very high rates. But there is a catch, they are EXPENSIVE, very expensive and require some special charging techniques. There is one manufacture out there that is very popular with EV DIY types. Unfortunately they are Chi-Coms called Thundersky.
          MSEE, PE

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          • #6
            Originally posted by Sunking View Post
            By now you should have already figured out Lithium is what you want as th eenergy density comes in at 90 to 200 wh/Kg. Some can be charged and discharged at very high rates. But there is a catch, they are EXPENSIVE, very expensive and require some special charging techniques. There is one manufacture out there that is very popular with EV DIY types. Unfortunately they are Chi-Coms called Thundersky.
            EnerDel any good? Made in USA
            http://evolveelectrics.com/Enerdel.h...FZRr7AodVgkAug

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            • #7
              Originally posted by FloridaSun View Post
              Really could not tell you as I have no experience with them. I looked at the specs on the MPS320-049 and they look OK and at around $1/wh a little pricey but not as high as some competitors.
              MSEE, PE

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