Thought experiment of rigging solar panel to electric bike, questions about LiFePO4

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  • lkruper
    replied
    Originally posted by HarperHurst
    First off, I am perhaps only a single step above someone who knows absolutely nothing about solar panels. I know some of the basics of electricity, and that's about it.

    A few days ago I began postulating the possibility of selling my old Kawasaki dirt bike and buying an electric bicycle. I then had the idea of rigging a solar panel to said bicycle. From my own research, I know that at a bare minimum I would need a solar panel (Duh.) and a solar charge controller.

    The e-bike which I have been looking at is the X-treme X-cursion mountain bike. It runs off a 24V 8Ah LiFePO4 battery.


    I would buy a 20-45 Watt 24 Volt Panel and rig it to the cargo rack in some way that it is secure and hopefully thief-proof.

    Throughout the course of my research I have found two types of solar charge controllers: PWM and MPPT. I am aware that PWM controllers apparently have a notable net loss of power, whereas MPPT controllers have much less. I'm all for maximum efficiency, so I'm sure I'd want an MPPT controller. I found this controller on Amazon that doesn't appear too costly and has great reviews even though it's a cheap "Made-in-China" product:


    At the end of the day I still have a few questions which need answering:
    1.) Would I need to buy a charge controller that is meant for charging LiFePO4 batteries, and is the one listed above able to do so? I've not found much in the way of the safety considerations for using controllers with different types of batteries.
    2.) Even with a compatible controller, part of me assumes it will not be easy (near impossible) to feed power directly from the controller into the bike's battery. Is my reasoning correct on this?
    3.) If my reasoning in #2 is correct, would it be then be necessary to purchase an inverter and some sort of cable to charge the battery similarly to the way it's meant to be charged? (Through the port on the battery wherever it is?)
    That's a neat bike! What problem are you trying to solve with solar? Are you planning a cross-country trip where you will not have access to power? If you carried a spare charged battery, I think you will be miles ahead of any solar charging.

    Leave a comment:


  • Thought experiment of rigging solar panel to electric bike, questions about LiFePO4

    First off, I am perhaps only a single step above someone who knows absolutely nothing about solar panels. I know some of the basics of electricity, and that's about it.

    A few days ago I began postulating the possibility of selling my old Kawasaki dirt bike and buying an electric bicycle. I then had the idea of rigging a solar panel to said bicycle. From my own research, I know that at a bare minimum I would need a solar panel (Duh.) and a solar charge controller.

    The e-bike which I have been looking at is the X-treme X-cursion mountain bike. It runs off a 24V 8Ah LiFePO4 battery.


    I would buy a 20-45 Watt 24 Volt Panel and rig it to the cargo rack in some way that it is secure and hopefully thief-proof.

    Throughout the course of my research I have found two types of solar charge controllers: PWM and MPPT. I am aware that PWM controllers apparently have a notable net loss of power, whereas MPPT controllers have much less. I'm all for maximum efficiency, so I'm sure I'd want an MPPT controller. I found this controller on Amazon that doesn't appear too costly and has great reviews even though it's a cheap "Made-in-China" product:


    At the end of the day I still have a few questions which need answering:
    1.) Would I need to buy a charge controller that is meant for charging LiFePO4 batteries, and is the one listed above able to do so? I've not found much in the way of the safety considerations for using controllers with different types of batteries.
    2.) Even with a compatible controller, part of me assumes it will not be easy (near impossible) to feed power directly from the controller into the bike's battery. Is my reasoning correct on this?
    3.) If my reasoning in #2 is correct, would it be then be necessary to purchase an inverter and some sort of cable to charge the battery similarly to the way it's meant to be charged? (Through the port on the battery wherever it is?)

    EDIT: I have been reading the stickied thread "Simplified lifepo4 charging and care" in this board and I have revised some of my hypotheses concerning this project.
    It seems the safety concerns about charging LiFePO4 batteries with solar versus say charging lead acid batteries is the individual cell voltages. Since I know that a battery is only as strong as its weakest cell, I know that unbalanced cells in a battery could lead to "reverse current," which is apparently devastating to LiFePO4 batteries. The 1st posts recommends that you check the cells when you first get the battery for any unbalanced voltages. Provided the cells are balanced (and stay balanced after charging) when you first get the battery, or you manually balance the cells (which hopefully stay balanced after charging) there would be no need for individual cell management. I'm guessing that if you also just perform routine checks to the battery's cells to make sure they're balanced (and balance them if need be) you could completely eliminate any possible need for a cell management unit built into the whole rig. Is this reasoning correct?
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