Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Hybrid question

  1. Mar 17, 2008 #1
    I want to add a secondary battery bank to the hybrid and have that send a charge to the primary battery.

    I am considering 2 wind turbines mounted in the radiator inlets.

    I want to have the turbines charge a secondary battery that will feed to the primary battery. I am doing this to prevent overcharge of the primary battery.


    Does a standard charge controller have the ability to charge to the secondary battery and prevent overcharge?

    Do I need to have a device to prevent the electricity from going back to the turbine and spinning the motor/turbine

    How do I send the charge from the secondary 12V secondary to the primary 330v battery? I have not been able to find a dc/dc converter for that high of a voltage.

    What is used to prevent the secondary battery from being totally drained. I want to have is cycle to no less than 30% of a remaining charge to aid in longivity.

    Is there anything specific for battery to battery charging that I need to know? I have had a hard time finding this information on the internet.

    thank you.
    Last edited: Mar 17, 2008
  2. jcsd
  3. Mar 17, 2008 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    You're talking about a hybrid-electric vehicle? A production vehicle you purchased from a dealer?

    Honestly, your questions indicate you have no idea what you're talking about and should leave well enough alone. The battery charging systems built into the vehicle will prevent overcharging of the battery pack. Your idea won't work for a wide variety of reasons, and might well end up getting you killed if you try to build it. High-voltage battery packs are not newbie-friendly environments.

    - Warren
  4. Mar 17, 2008 #3


    User Avatar
    Gold Member

    Welcome to PF, Lasix.
    In addition to the very real safety concerns raised by Chroot, you would be losing the game right from the beginning. The added weight of the auxiliary batteries and the aerodynamic drag from the turbines would you cost far more energy than you could ever recover. The turbines themselves would mean that you wouldn't be able to use the IC engine even if you wanted to, since the radiator wouldn't be getting enough air to keep it cool.
  5. Mar 17, 2008 #4
    No offense chroot, I know you meant well, but your post was useless to me. If you think it's a bad idea state why. I might end up getting killed driving to work, maybe I shouldn't do that either?

    I do know what I am talking about. I don't know how to build it. There is a difference. I am here so I don't kill myself or damage the truck. The battery in the hybrid does prevent overcharging, but it is difficult to charge it directly because if it senses a charge when one should not be present it will cause a CEL (check engine light). A secondary battery is needed to store the charge so it can be sent to the primary over time and not in surges. I would need to experiment with exactly what amperage the CEL threshold is. Can you assist me in finding a charge controller that can charge a 330v system with variable amperage output, or do you have any other suggestions besides leave well enough alone?

    Danger, thank you for the welcome :) I am looking to add 1 to 2 deep cell batteries (80 lbs).

    2 400 watt gens each with a 12 in blade diam. Air passes through the turbines and will continue on through the radiator, I don't see how that will prevent the use of the ICE.

    Also, there will be minimal added drag because this is mounted in a place where there is already a lot of drag, the front of a truck.

    I don't want to get into a debate regarding thermodynamics. So before you go there, if I removed the fog lights, put a smooth tube and ran the tube from the fog light opening and created a new opening on the side fender, then placed a small wind turbine inside that tube (think inline fan), I would actually decrease the drag on the front of the truck (making it more efficient), by allowing the higher air pressure in the front of the truck to move in a more direct rout through the tube (if it wasn't more efficient then the air would not pass through the tube). In turn it would spinning the turbines creating electricity as the air moved from higher to lower pressure areas... maybe that would be a better way to go. But that's in the finshing details.

    For my weekly driving that's potentially 2KW/day of usable energy, or apx 1 gallon of gasoline/week of saved energy.
  6. Mar 18, 2008 #5


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    The old expression, "There aint no such thing as a free lunch" applies here. Even if your fans are hidden under the hood it still requires energy to drive them. That energy must come from your battery or gas tank. You will see reduced gas mileage and battery life. Because of the friction and loses in your added components the charge added to your extra batteries will be less then the charge removed from your primary battery which is used to drive your fans.

    Beyond that, it is the batteries which rend your hybrid much less "green" then you believe it to be. Your extra batteries turn your hybrid from just about green to an environmental disaster area. It is bad enough already, just leave it alone.
  7. Mar 19, 2008 #6
    Really rough equation to show the energy that could be gained:

    energy provided from the battery is going to be the energy to move the truck (KE), plus energy to overcome friction (Ef), plus energy to overcome drag (Ed):
    Eb = KE + Ed + Ef

    with the turbin lets say it takes about 10% of the drag and converts it into energy for the 2nd battery, Eb2, (ignore engine energy, that he thinks it might make total drag less, and that the conversion is 100% efficient) then:

    newEd = Ed = Eb2 + .9*Ed

    so that

    Eb = KE + newEd + Ef

    Eb = KEt + Eb2 + .9*Ed + Ef

    but you get to keep Eb2 in a battery for later use rather than wasting it away to drag so effectively the whole change has dropped his Drag Energy by 10%, which would give him a savings in energy and fuel. This is assuming that his turbines take up enough area and are big enough to take in 10% of the drag and does not create more drag than there would be without them.

    Now when you're not moving, you can charge Eb with Eb2 (this is one of the complicated designs that should not be modded on a truck for everyday use by a nonprofessional) and basically get back what you would have lost to the energy to fight drag.

    so instead of putting 100% of the Battery energy (or engine energy) required to overcome drag you're putting 10% of that back into your battery, similar to regenerative braking taking the KE of the car and converting it into electrical energy because you HAVE to break, just like you HAVE to have wind resistance. Its not ideal to convert the battery energy into KE and then convert it back to battery energy, but you do it with regenerative breaking just like you would with wind resistance.

    Not trying to say he is right and you're wrong, but I think some of the basic reasoning makes sense and you can't necessarily say he's trying to get something from nothing, unless I'm overlooking something. I tried to prove it above. But, there still is the whole issue of lots of technical problems and inefficiencies though that even a lot of professional engineers would have a hard time overcoming. I think this man would have a much simpler, less expensive, and less dangerous experiment by just trying to lower the wind resistance of his truck rather than trying to capture the energy lost from the wind resistance his truck generates; it would essentially be combating the same problem with a simpler and safer solution.
    Last edited: Mar 19, 2008
  8. Mar 19, 2008 #7
    But your turbines will have essentially removed the pressure that forces the air to move over the radiator right? I never studied fluids and air flow to understand turbines that well, but doesn't the radiator need air to flow through its fins to dissipate the heat?? Or else you're relying on all the heat transfer to be from conduction and none with convection. This makes me wonder how you could run a car in park and rev the engine without overheating the engine now . . maybe i'll make a new thread for that question :confused:
  9. Mar 19, 2008 #8


    User Avatar
    Gold Member

    That's what the fan is for.
  10. Mar 19, 2008 #9
    lol I didn't know about a fan . . you can tell how much I know about cars now. So if there's a fan, then what is the worry about not having air to cool the radiator??? Is the fan going to have to fight with the turbines?
  11. Mar 19, 2008 #10


    User Avatar
    Gold Member

    Essentially, yes. Since the turbines are extracting work from the incoming air, they're also causing a restriction which will decrease the amount of air that can pass through. It would be like trying to breathe with a whistle stuck up your nose.
  12. Mar 19, 2008 #11


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Best. Analogy. Ever. :rofl:

    - Warren
  13. Mar 20, 2008 #12
    Hybrids, Smybrids. Water power is the energy of the future.
  14. Mar 20, 2008 #13


    User Avatar

    Staff: Mentor

    Great visual, too.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook