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How about 2 12 volt batterys??

Discussion in 'Gen 2 Prius Fuel Economy' started by Speedking, Oct 10, 2011.

  1. Speedking

    Speedking Junior Member

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    Has anybody thought about installing another 12 volt gel cell to hold power longer and may increase MPG?
     
  2. fuzzy1

    fuzzy1 Senior Member

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    I don't follow. How would it increase MPG?
     
  3. F8L

    F8L Protecting Habitat & AG Lands

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    I agree with fuzzy. How would this increase mpg?

    You really don't need two batteries unless you plan on building a high wattage stereo system or other high draw accessories.
     
  4. Speedking

    Speedking Junior Member

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    I would think it would take longer to discharge so it would take less energy to re-charge.

    Just a thought. like using a deep cell for boats.. They hold power longer…
     
  5. RobH

    RobH Senior Member

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    Now who on earth would do that with a Prius? :D
     
  6. qbee42

    qbee42 My other car is a boat

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    Won't work. It takes the same amount of energy to charge either way, but with two batteries you carry twice the weight. It will actually hurt your mileage just a tad.

    Tom
     
  7. F8L

    F8L Protecting Habitat & AG Lands

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    Hush, Rob! lol

    Tom is correct. The energy spent to recharge the two batteries is the same as one battery assuming there is not a resistance change when wiring in two batteries.
     
  8. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    But there is a resistance change because now you have 2 in parallel.

    But overall, not going to make a shred of difference and any offset gained by the marginally less ohmic load will be destroyed by carrying around a gigantic dead weight 99.9% of the time.
     
  9. fuzzy1

    fuzzy1 Senior Member

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    And don't forget the doubling of the battery self-discharge, another loss mechanism.

    But I'll agree that the extra weight is the largest factor.
     
  10. tf4624

    tf4624 Active Member

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    Who would do it. Or who has lol I might have.....
     
  11. 2009Prius

    2009Prius A Wimpy DIYer

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    Someone did a "mild plug-in" by adding a 14V deep cycle battery to the 12V system (with some electronics of course). The 14V would be charged to full at home. Then it provides the charging voltage in READY mode while driving so the DC-DC converter won't need to do any work until the 14V battery runs low and gets switched out.
     
  12. vertex

    vertex Active Member

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    2 batteries will decrease your gas mileage, you will be carrying around a few extra pounds all the time. The advantage of a larger capacity 12 volt battery (either by putting in a physically larger unit with higher capacity, or 2 batteries in parallel) is that you will have a longer time that you can leave the car parked with out using it. I think the recommendation is now to start it once every 3 weeks. That could be extended with more capacity. Also, you would get longer operation in accessory mode, when the hybrid system is not ready. For most people, it would be a waste to do.
     
  13. V8Cobrakid

    V8Cobrakid Green Handyman

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    i've had a very larger tractor battery as my 12v for a while.. all this post is really about, is the ability to leave your car sitting for long periods of time... or... thinking you'll somehow pull more power with your reserve battery than the car can handle... (dangerous)

    there is one key thing since i see your only have 3 post.. and you mentioned gel battery as if the car runs off 12v....

    this car does not use the 12v for powering the car... only for switching on a few computers... then the 250V (roughly) hybrid battery runs the car.

    there are kits for this exact purpose already. they cost between 5 and 15 grand (from what i've seen)