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Regenerative breaks - charge / discharge battery chemistry

  • 12-10-2019 9:35pm
    #1
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭


    Hi,

    Still don't get the smart processes behind the regenerative brakes...
    Changing the battery's poor pissed electrons from discharging to charging to discharging again, their flow inversed in a matter of seconds, too much for them poor guys.

    How does that work, from brakes mechanical and BMS electronical controls to the chemical processes inside the battery !??

    Thanks


Comments

  • #2
    liamog
    Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 7,792 Mod ✭✭✭✭liamog


    An electrical motor and generator are essentially the same thing.

    When you send an electrical current to the motor it rotates and provides forward motion.
    When you add load to an electrical generator it increases mechanical resistance.
    The motor converts electrical energy into kinetic energy, a generator converts kinetic energy into electrical energy.

    When we attempt to slow down a vehicle we need to discard some of its kinetic energy. With classical brakes, this was done using friction to create thermal energy.
    Regenerative braking allows us to draw a current from the motor (turning it into a generator). This allows us to convert the kinetic energy into electrical energy. This can then be sent through the inverter back to a battery and stored for future use.


  • #3
    Markcheese
    Registered Users Posts: 8,428 ✭✭✭Markcheese


    Medium term, it'll probably be super capacitors that'll take up and release the charge from regen... (Especially with heavy vehicles/buses),
    Less energy dense, but more responsive... And takes pressure off the batterys...

    Slava ukraini 🇺🇦



  • #4
    unkel
    Registered Users Posts: 64,725 ✭✭✭✭unkel


    Markcheese wrote: »
    Medium term, it'll probably be super capacitors that'll take up and release the charge from regen... (Especially with heavy vehicles/buses),
    Less energy dense, but more responsive... And takes pressure off the batterys...

    The forte of super capacitors is more to do with accelerating than braking!

    And even more to do with fast charging than any of the above!

    But I guess we don't know yet, these are just my musings on the subject at the moment...


  • #5
    Markcheese
    Registered Users Posts: 8,428 ✭✭✭Markcheese


    I though supercapacitors were good at taking In the high currents from a hard regen... And then putting out that current again in a very short space of time, they use them on container cranes in ports, lousy energy density (compared to a modern battery), but brilliant for stop start applications, either in conjunction with a battery or a diesel electric set up...

    Slava ukraini 🇺🇦



  • #6
    Lumen
    Registered Users Posts: 31,008 ✭✭✭✭Lumen


    Markcheese wrote: »
    I though supercapacitors were good at taking In the high currents from a hard regen... And then putting out that current again in a very short space of time, they use them on container cranes in ports, lousy energy density (compared to a modern battery), but brilliant for stop start applications, either in conjunction with a battery or a diesel electric set up...

    It doesn't really matter whether the electricity is going in or out, the supercapacitor can act as a buffer to reduce peak current.

    Presumably it'll be held at medium (50%?) SoC at cruise so that whether you brake or accelerate, it can buffer the charge.

    How much buffer? Dunno. Five seconds at 300kW is what, 1.5MJ, or 0.42kWh. So 1 kWh would be plenty. But currently would cost thousands.

    1.5MJ is enough to get an 1800kg car to 147kph (before aero, rolling and drivetrain efficiency losses).


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  • #7
    unkel
    Registered Users Posts: 64,725 ✭✭✭✭unkel


    Lumen wrote: »
    1.5MJ is enough to get an 1800kg car to 147kph (before aero, rolling and drivetrain efficiency losses).

    How did you calculate this last bit?


  • #8
    liamog
    Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 7,792 Mod ✭✭✭✭liamog


    Any extra circuitry such as a supercapacitor should only be needed if the car has an asymmetric charge/discharge rate.

    The max braking force the motor can deliver is equivalent to the max motive the force the motor can deliver.
    For instance, the Hyundai Ioniq has an 88kW motor, we know the drivetrain is capable of supplying 88kW. The highest number I ever recorded going into the battery during regen was 84.3kW.


  • #9
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭rolion


    Thanks.

    I tought that the "generators" are built in the wheels and they are charging the battery when braking needed.
    In the case of Outlander,there are two electrical engines...


  • #10
    Lumen
    Registered Users Posts: 31,008 ✭✭✭✭Lumen


    unkel wrote: »
    How did you calculate this last bit?

    https://www.calculatorsoup.com/calculators/physics/kinetic.php


  • #11
    Lumen
    Registered Users Posts: 31,008 ✭✭✭✭Lumen


    liamog wrote: »
    Any extra circuitry such as a supercapacitor should only be needed if the car has an asymmetric charge/discharge rate.

    Technically yes, but maxing out that rate without buffering through a supercapacitor accelerates battery degradation.

    So with a supercapacitor you can maximize performance and battery life.


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  • #12
    rolion
    Closed Accounts Posts: 3,362 ✭✭✭rolion


    SO... after we sorted out the suprainductocapacitors flux controls time circuits by our specialists...

    May i ask you the mechanical principle first, please !?
    So,the electrical engine spins clockwise and drives the car forward powered by the battery ... then same electrical motor spins anticlockwise and slows down the car when speed is slower than the something !?

    All done by the same axle under the car.... clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise , anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise ...

    No effects by the wheels brake pads until you press the foot pedal.
    And i even touched the BMS and the battery....


  • #13
    Markcheese
    Registered Users Posts: 8,428 ✭✭✭Markcheese


    rolion wrote: »
    SO... after we sorted out the suprainductocapacitors flux controls time circuits by our specialists...

    May i ask you the mechanical principle first, please !?
    So,the electrical engine spins clockwise and drives the car forward powered by the battery ... then same electrical motor spins anticlockwise and slows down the car when speed is slower than the something !?

    All done by the same axle under the car.... clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise , anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise, clockwise ,anticlockwise ...

    No effects by the wheels brake pads until you press the foot pedal.
    And i even touched the BMS and the battery....

    What.?? Its the motor.... Basically if there's electrical current going in theres rotational energy going out... But if there's mechanical energy going In it generates electricity...
    But it stays turning the same way....

    Slava ukraini 🇺🇦



  • #14
    Water John
    Registered Users Posts: 21,113 ✭✭✭✭Water John


    It's a generator or a motor, uses power or generates it.

    This is used in electrical pumped water storage. The pump motor rises the water at a time of cheap current and the falling water drives it as a generator when current is needed. Highly efficient about 80%.


  • #15
    zilog_jones
    Registered Users Posts: 6,641 ✭✭✭zilog_jones


    rolion wrote: »
    ...electrical engine...
    It's called an "electric motor" ;)
    Or more specifically motor-generator
    All done by the same axle under the car.... clockwise ,anticlockwise...
    Do you put your traditional ICE car into reverse to slow down? :eek: The motor is not changing direction, the flow of energy is.
    No effects by the wheels brake pads until you press the foot pedal...
    Depending on driving conditions and brake pedal position, it still could only be doing regen.


  • #16
    Water John
    Registered Users Posts: 21,113 ✭✭✭✭Water John


    The balance between regen and brakes depends on what level of regen you set it at.
    On main roads, I drive the leaf in D with Eco off, on by roads and city I drive in B with Eco on. Like driving two different cars.


  • #17
    liamog
    Moderators, Motoring & Transport Moderators, Regional East Moderators Posts: 7,792 Mod ✭✭✭✭liamog


    Water John wrote: »
    The balance between regen and brakes depends on what level of regen you set it at.
    On main roads, I drive the leaf in D with Eco off, on by roads and city I drive in B with Eco on. Like driving two different cars.

    Depends very much on the car. For Hyundai, the regen setting only affects the amount of regen when you lift off the accelerator. When you press the brake pedal the car will regen with as much force as it can muster. The harder you press the more disc braking it will blend in to help slow the car.

    My e-Up! works the same.


  • #18
    Water John
    Registered Users Posts: 21,113 ✭✭✭✭Water John


    When you turn off Eco on the Leaf you have much more acceleration as well so it drives quite differently overall.


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