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SOLAR PANEL AMPERAGE LIMITER (overpowering)

Discussion in 'Renewable Energy' started by john gould, Jul 7, 2015.

  1. john gould

    john gould New Member

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    I am building a 3 wheeled bike that runs with on 24v assist motor and lithium lip04 batteries.

    I found a controler that will take 24-35volts and convert it to the proper voltage for charging the battery, BUT.. I was tole that once I have the battery and the controler I must then scale down the solar panel to match the maximum apperage to feed the battery, or it will not take a charge due to an internal amperage feed limitations.

    The problem is I only need 6 amps (due to battery size & cost) at a voltage of about 28volts to feed my controler (which has a 20amp max flow through) so I get maximum charging at all times. I want the bigest 300 watt panel I can fit on the bike. A 150 Watt (max) panel is not going to do me much good on a cloudy day so the big panel, with a limiter (of sort) when the sun is really bright is what I am after.

    300watt @28 ave. volts 10.7 amps. Is there a dump controler that will only let 168 Watts pass through?

    Make sense? I'm new at this stuff, but good with numbers
     
  2. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    No.

    If the battery can supply 20A, then it can charge at 10.7. YOu just have to limit the current from overvoltage
    why do you have to limit 168W?
     
  3. john gould

    john gould New Member

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    In hot dry conditions the panel will put out 12 amps & the battery circuit board cuts off if the amperage is over 8.

    I need to limit the solar panel at hot times. My problem is supplying the battery with useable current (6amps @ 28.5v)
     
    Last edited: Jul 7, 2015
  4. dave

    Dave New Member

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  5. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    without a block diagram and specs on each unit, it is hard to decide what is best other than general regulation methods , which you ought to know like an MTPP controller. with voltage and current limiting while optimizing PV voltage for max power.

    http://www.magna-power.com/products...supplies/photovoltaic-power-profile-emulation
     
  6. Colin

    Colin Member

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    How many watts is the motor?
     
  7. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    If PV is driving motor then battery current is reduced. If not and Vbat is at max, the PV must open circuit. Thus can be done by MOSFET with PWM and series L to smooth current (with fast reverse recovery diode) and regulate PV PMT when needed or vbat max when not needed.

    If your board cannot handle max motor current due to PV max input with load, then design changes with your details supplied are necessary somewhere.
     
    Last edited: Jul 8, 2015
  8. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Okay? So how are you planning to attach a set of solar panels that are nearly the size of a sheet of plywood to your bike and keep them all pointing toward the sun while moving?o_O
     
  9. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Good point, tc. The smallest 300W panel I saw in a quick Google had this description:-
    That's a sail. You won't need a motor :).
     
  10. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Yea but he wants the biggest 300 watt panel he can get. :facepalm:

    I get the impression that the OP has not done or understands all the engineering, physics and physical implementation of parts behind his project. :oops:
     
  11. Tony Stewart

    Tony Stewart Well-Known Member Most Helpful Member

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    A 300W panel @15% efficiency need 2x1m panel. Voltage of battery should be 70-80% of no load V for no current regulation and overvoltage on idle use, can be a Transistor to open current or turn off switch at 14.2V per 12V battery.
    Then motor must be matched to Vbat .
    Much more work needed.

    If it were 36V bat and 36V motor then 44Voc PV might work otherwise DC-DC converter wastes power to 24Vmotor.
    http://www.affordable-solar.com/sto...els/Canadian-Solar-CS6X-300P-300w-Solar-Panel

    Options for 24V panels http://sunelec.com/solar-panels/24v-solar-panels

    Often size is reduced with higher efficiency at more cents per Watt. Or wait 5 yrs for price to come down.

    It may end up cheaper to put more storage power in batteries and charge offline between uses.
    Say if a 30 lb battery gives 50Ah at 12 or 600Wh then it is 20Wh per pound and compare on bicycle power machine your power per pound weight and drag with motor and battery duration power per pound .

    This is a big tradeoff in solar powered cars. To maximize Wh/pound or kg.
    Use this to compare deep cell capacity/wt.

    http://www.instructables.com/file/F0RVX9VI77WP829/?size=LARGE
     
    Last edited: Jul 9, 2015
  12. tcmtech

    tcmtech Well-Known Member Most Helpful Member

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    Unless he is planning to do some long distance traveling I would suggest setting up the solar panels as a stationary charging system and adding extra battery capacity over trying to mount solar panels to the bike.

    Now just taking a wild guess at things here given a 300 watt maximum and a 6 amp battery capacity I am envisioning a drive system that is of less power and range capacity than my 6 year old daughter's electric scooter which I have set up with a 24 volt 8 ah battery system and the motor is rated at something like 500 - 600 watts. Which to be honest with her on it weighs maybe 80 pounds and is fairly zippy. Now however with my full sized adult body putting the total weight up around 270 pounds the thing is slow and way under powered.

    Given that a assumed 300 watt drive system on a three wheeled bike carrying an adult plus ~2 sq meters of solar panels I would dare say that the thing is going to be about as fast as a mobility scooter assuming it's not pushing a headwind. :sorry:
     

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