1. Attachments are working again! Check out this thread for more details and to report any other bugs.

capacitor bank

Discussion in 'Prius PHEV Plug-In Modifications' started by 2007blueprius, Nov 22, 2013.

  1. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I guess this could work in a regular prius too not just a phev, but seemed like a good place to post it,
    I was trying to wrap my head arround batery management systems and I came across capacitor banks wich are supposed to help with high loads, now I do not know enough about it but I thought that a capacitor bank could help recover more energy during regen braking and also take some beating so that the stock battery doesnt have to .
    I know the stock batery runs at about 220v, and than there is an inverter that steps it up to 650v now in pure ev aplication there is also a moptor controller, I asume the prius has one too, the hybrid ecm they call it, questin is if one were to atempt such a capacitor bank, what size would it have to be and where would it go? the mg1 mg2 are ac motors if I am not mistaking and capacitors are dc, so it would have to be on the battery side I would say.
    the 650v the inverter outputs I assume is ac, as well as the regen current comming from mg2, like I said I do not know enough so any thoughts?
     
  2. mrbigh

    mrbigh Prius Absolutum Dominium

    Joined:
    Sep 6, 2005
    3,686
    699
    2
    Location:
    Long Island, NY
    Vehicle:
    Other Electric Vehicle
    You have to do a lot of reading, search in Wikipedia about Prius PHEV operation, technology and components.
     
  3. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    thanks for stating the obvious, don't get me wrong I am not clueless but no where near knowledgeable, as for articles like wikipedia, there is nothing on there that I do not know about or that would provide a clue as to weather a capacitor bank is a feasable mod or a bad idea or rubbing a woden leg beating on a dead horse etc.
    I was actually hoping somebody with somewhat experience would consider the thought and pitch in some ideas as to how to go about it and what to expect.
    my experience with capacitors, I used to work with airconditioning units, and most compressors, even brand new ones wont start wihout one, rarely a fluke one may start but I never bother to try it they are built to use one, simply because there is not enough power in the supply to turn them 220v @30 amp, the capacitors on most had 3 terminals, comon run and start, some just a start, and even most fans would need one, I have seen them anywhere from 35mf to 5 mf.
    I know they add up funny unlike batteries series is sum of 1/c, and most I worked with I believe they were rated for 370v
    I know they take a charge very quickly and can discharge just as fast but they do not hold up much or for long for thet matter, further more there were jumppacks available if you have an old stuborned compressor that wont start in the spring one of those woul get it going again it would start thereafter till next spring eventually givving up.
    I have read that in the prius especially at regen some large ammounts of amps are generated, theat is where I figured a cap bank could take the charge and either slowly bleed it into the batery or bounce right back at acceleration but that may get the computers all confused, may improve with efficiency, may even improve performance, may also blow something up.
    so has anyone else ever considetred the thought?
     
  4. mrbigh

    mrbigh Prius Absolutum Dominium

    Joined:
    Sep 6, 2005
    3,686
    699
    2
    Location:
    Long Island, NY
    Vehicle:
    Other Electric Vehicle
    The topic of a capacitor bank was discussed here some years back withing PC selected members, when suitable capacitors where at premium price and sort of scarce to get. The idea was deem for an inappropriate application vs. cost.
    Now days, some major Automotive manufactures/fabricators are heavily using them in F-1E racing vehicles. But seems that only them can afford such a adventurous expenditures.
    You still will get more range and all the added benefits increasing the OEM PHEV/EV battery pack.
     
  5. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    that is kind of the input I was looking for, has anyone considered using common household/ industrial electric motors capacitors widely available and relatively cheap, than again I do not know what size of a pack one would need to build at least in theory therefore how many it would take, I searched for such a thread and came up empty, from what I remember your average AC compressor cap is 35 mf 370v, I have to go have a look at mine to confirm, these used to be a few bucks, a jumper ( as I mentioned previously used to get those older units going in the spring ) was about 15, I used to have shelves full of them at work, wonder how many it would take to build a pack, even 100 of them would be about 500 - 600 especially in large quantities, again not sure if those spec caps would even be feasable,
    I'll try to find that thread
     
  6. dan2l

    dan2l 2014 Prius v wagon

    Joined:
    Nov 26, 2009
    654
    263
    5
    Location:
    Vancouver Wasington
    Vehicle:
    2014 Prius v wagon
    Model:
    Five
    Hello Blue,
    If my memory is correct, a farad gives 1 volt at 1 amp for 1 second. So we need kilo or mega farads and you are talking milli farads.

    So you need millions or billions of those blue cylinder caps.

    Thanks,
    Dan
     
  7. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I have seen some built capacitor banks and they are huge I'll give you that, like I said I do not know enough, it's a thought that crossed my mind while looking up other phev stuff figured I'd bring it up, I haven't foud too much info as far as to what specs they are built, there is a you tube video looks like he has 10 of them and they are the size of a 2 liter, but not a whole lot of info as to specs or the batery pack it is in conjunction with, etc
     
  8. drysider

    drysider Active Member

    Joined:
    Apr 14, 2008
    823
    332
    1
    Location:
    Liberty Lake WA
    Vehicle:
    2012 Prius
    Model:
    Four
    Actually, it is 370 microfarads. The problem with current technology capacitors is that they have a very low energy density compared to batteries. Their big advantage is that they can be charged very, very quickly if you can provide the necessary energy, and they can discharge that energy very, very quickly. That is why the race car folks like them. A hybrid battery-capacitor storage system is probably not far away.
     
  9. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I do not remember what a farad was, but I am pretty suer those common caps were rated ar 35 micro farads, 370volts, theyr role was it to give that motr an initial jolt, some of these motors were 220v with 30 amp fuses so do the math , the prius motor can take what something loke 650v at what amps?
     
  10. dan2l

    dan2l 2014 Prius v wagon

    Joined:
    Nov 26, 2009
    654
    263
    5
    Location:
    Vancouver Wasington
    Vehicle:
    2014 Prius v wagon
    Model:
    Five
    Hi Blue,
    No, The Caps do not provide any power to the motor What they do is to give a phase shift to the 60hz 110Vac going to the starting winding. That provides a magnetic field that is phase shifted from the normal windings so that the motor will start. All the power comes from the 110Vac input.

    Thanks,
    Dan Lander
     
    ftl likes this.
  11. vskid3

    vskid3 Active Member

    Joined:
    Jun 23, 2013
    773
    228
    0
    Location:
    Texas
    Vehicle:
    2005 Prius
    The capacitor bank would be placed in parallel with the battery. However, the gains would likely be so small that sneezing out the back window would help you more. If anything, a second battery pack would make more sense.
     
  12. Bill the Engineer

    Bill the Engineer Senior Member

    Joined:
    Jun 6, 2013
    1,048
    2,278
    467
    Location:
    At the beach in Delaware...
    Vehicle:
    2010 Prius
    Model:
    IV
    I am an engineer for a major transit bus manufacturer. A company named Vanner makes a capacitor bank that is used in transit buses in parallel with the 24v batteries. It is large enough to fill most of a Prius cargo area, but it only provides enough energy to start the bus engine. There is not enough capacity to propel the vehicle.

    BTW, the Hybrid transit buses seen in the USA now use the same HV batteries as a Prius, just many more of them!

    Bill
     
  13. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I thought they would have a total different purpose, I had read that they can take a charge much larger and faster that a battery can just capacity is not much, so the idea was to use them as a buffer to take in the large amps from regen that the battery cannt handle or at least is what I thought they would do, I think that is the ideea in those racecars
     
  14. vskid3

    vskid3 Active Member

    Joined:
    Jun 23, 2013
    773
    228
    0
    Location:
    Texas
    Vehicle:
    2005 Prius
    Toyota programmed the Prius to not give the battery more than it can take. Regen isn't an uncontrolled waterfall of power, the computer can choose how much to do. Considering that most batteries last over 100k miles, I'd say it does a pretty good job.
     
  15. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I get that, and that's why the thought interested me, I figured some of the regen is getting dumped if you will because the batery can not handle it, a capacitor probably could
     
  16. vskid3

    vskid3 Active Member

    Joined:
    Jun 23, 2013
    773
    228
    0
    Location:
    Texas
    Vehicle:
    2005 Prius
    The regen over what the battery can take is dumped by the friction brakes or spinning the ICE if in B. Unless you modify the computer, the car likely won't take advantage of the capacitors.
     
  17. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    yeah good point, so B is for engine brake? it doesn't necesarily recover more energy in B, i did not know that, I guess the whole EV drivetrain would have to be built to incorporate a capacitor bank not just a simple upgrade
     
  18. vskid3

    vskid3 Active Member

    Joined:
    Jun 23, 2013
    773
    228
    0
    Location:
    Texas
    Vehicle:
    2005 Prius
    I believe B does more regen when you take your foot off the pedal vs D, but the max regen when pressing the brake is still the same, 100 amps or so.
     
  19. 2007blueprius

    2007blueprius Member

    Joined:
    Dec 26, 2012
    461
    30
    0
    Vehicle:
    2007 Prius
    Model:
    N/A
    I came across that 100 amp number before and I think that was one of the issues with doing away with the hv battery in phev converssions, 40 ah lithium cells can't handle it, gues that's where the caps could come in,
    I suppose the controler could pump more than 100 amps in some situations but that is probably getting complicated reprograming spooofing........... I get lost there
     
  20. Opmeyer

    Opmeyer New Member

    Joined:
    Aug 31, 2015
    2
    0
    0
    Location:
    Melbourne
    Vehicle:
    2009 Prius
    Model:
    II
    Hello, this is my first time posting here and was attracted by this interesting idea that I have been thinking about over the years.

    The pretext to my question leads on nicely from the discussion on this thread and I want to confirm some things that I understand to be correct:

    1) The prius MG 2 engages for regenerative braking to supply 100 to 500VAC to the bi-directional inverter, producing a 201.6VDC
    2) The 201.6 VDC charge generated can be up to 55Amps on MG2, producing 11kW.
    3) The charge controller monitors the temperature and state of charge of the battery and tells the transmission to apply engine braking through the ICE or engage the generator. Therefore the charge controller does not electrically shunt excess energy.
    4) The rate of charge of the battery is not known. Assuming 66% energy capture from the 11kW source at the inverter: the yield from the inverter would be 7kW.
    5) My assumption is that the batteries charge from regenerative braking until full or until they become warm at a rate of 201.6V / 7KW
    6) 1 Farad delivers 1 Amp for 1 second at 1 Volt

    Given the above observations
    I did some basic math to work out how big a capacitor bank would need to be to capture 3 seconds of regenerative braking energy.

    201.6V @ 55 A x 3 secs = 33264 Farad

    Could someone who knows more about electrical engineering of regenerative braking in a Prius please tell me if I am correct?