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Solar bike project, electrical questions

  1. Sep 5, 2009 #1
    I’d like to get many opinions and suggestions about possible configurations for a solar powered bicycle. Currently, my plans are to purchase an electric bicycle with 200-400W motor. There are many of these available on the market and many use a 24V/10A onboard battery (Typically NiMH) mounted to the frame.

    My project is to build a solar-power bicycle trailer, a small 60W solar array (40"x58") that would be mounted in a teeter-totter fashion (to adjust sun exposure from side to side). I’ve decided use two 12V 18AH Sealed AGM batteries connected in series for storing solar power and I am planning to use a solar charge controller with the following specs-

    Steca PR 1515
    System Voltage: 12 V (24 V)
    Max Module Input Short Circuit Current: 15A
    Max Load Output Current: 15A
    Max Self Consumption: < 5 mA
    End of Charge Voltage (Float): Liquid 13.9 V / (27.8 V) Gel 14.1 V (28.2 V)
    Boost Charge Voltage, 1h: 14.4 V (28.8 V)
    Equalization Charge (deactivated for gel) 1h: 14.7 V (29.4 V)
    Reconnection Setpoint (SOC/LVR): > 50% SOC / 12.6 V (25.2 V)
    Deep Discharge Protection (SOC/LVD): > 30% SOC / 11.1 V (22.2 V)

    My questions involve how the solar power system is connected to the bike. The charge controller has 6 terminals (solar input, battery and load). It auto-switches from 12/24V systems, so I assume it provides a 24V output when it senses a 24V battery.

    Question#1: What considerations must be made when connecting the output of the solar charge controller to the electrical system of the bicycle? Would I need to always isolate the Bike’s onboard battery from the solar output? I had originally planned on connecting the solar controller's output directly to the NiMH onboard battery with a toggle switch in between. I know this will cause charging of the HiMH and I’m not sure if that behavior can be managed safely or if it’s better to avoid it completely.

    Question#2: What is the ideal configuration for the solar panels? There are 4 that make up the array and they are rated at 1A each “ideal.” I’ve ordered these panels but they have not arrived yet, so I’m not sure how much peak voltage they provide in full sun. But, in general, would it be best to wire these in series or parallel? Or possibly series and parallel? What would be the benefits or limitations of both?

    Disclaimer: I know the solar panel is too small to power the bicycle directly. The idea is to take it camping, etc. where there would be frequent stops and ample time to slowly charge the batteries. This is just a fun project I thought I would take on for the sheer fun of it.

    Thanks to everyone in advance. I hope you have as much thinking about this as I do!

  2. jcsd
  3. Oct 11, 2010 #2
    Hello Kelly,

    You can view my new website here, where I describe a solar bike project. It is not finished yet, but is will answer perhaps some of your questions.

    http://www.avdweb.nl" [Broken]

    Last edited by a moderator: May 5, 2017
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