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Well, some asked for it, so I'm doing it--Lithium Drop in replacement for Aux Battery

Discussion in 'Model S: Battery & Charging' started by islandbayy, Jul 9, 2013.

  1. islandbayy

    islandbayy Active Member

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    Well, it's been talked about, questions have been asked, the why's and why not's etc...

    So, I have my test battery in hand, I have been experimenting with it. Lithium Iron Phosphate. It should be a direct plug and play drop in battery by the time I'm done.

    I will update here with the details. My next step is installing it in the car and seeing what happens.
    My only concern, is how the MS charges the Aux battery. Only when it gets to a certain voltage? Or just tops it off regularly. Because, Lithium keeps it's voltage up until it's just about had it, my only concern is that by the time the car senses that the battery is low, it's already too low for the car to start the charge, and will require external charging.

    The battery I am testing is 28 Amp Hours. I'm told the Lead Acid Aux battery is 30 amp hours. That will not make a difference as the Lithium is more Efficent to begin with. This battery actually had enough cranking amps to start my work truck, and thats the best it has ever cranked in it's life, and I am also looking into using them for the Scooters I sell.
    The Lead Acid Batteries in the MS are about 28-32 Lbs in weight, my lithium replacement is about 3-4 lbs.

    I get my MS60 back from Villa Park service center Wednesday, will need to give back the MS P85 :( But am installing it and starting testing in real world once I get my MS60 back.



    I will update, and will offer for purchase if/when my testing is complete and if successful!
     
  2. steve841

    steve841 Active Member

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    Do you operate a manufacturing facility?

    i use Li Fe batteries on my motorcycle and love them......
     
  3. dsm363

    dsm363 Roadster + Sig Model S

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    Nice work. What is the cost comparison between what you are making and what Tesla pays for off the shelf? Maybe you could be a supplier to Tesla for this upgraded component.
     
  4. Al Sherman

    Al Sherman It's about THIS car.

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    Wow! Gutsy move Mav. Looking forward to reading your update.
     
  5. wycolo

    wycolo Active Member

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    #5 wycolo, Jul 10, 2013
    Last edited: Jul 20, 2013
    > My only concern, is how the MS charges the Aux battery. Only when it gets to a certain voltage? Or just tops it off regularly. [islandbayy]

    These charts have been posted here on TMC; search on '12v battery'.

    [ TM uses a regular 12 volt AGM battery with NO internal module or connections. End of that rumor/speculation ]

    Lacking a properly modularized 12v battery replacement, high tech or otherwise, that could be stored in the frunk and connected up should the original fail, has led to a defensive stance:

    a: Don't leave home without checking the 12v system voltage (i.e. plug in a voltmeter to the 'cigar lighter' outlet). This should read at least 12.6v, if not call Service.

    b: Carry a 12v 'garden tractor' battery in the frunk. Bring out wires from the original 12v battery so this spare battery could be connected in case it is needed, to open doors, turn car ON, limp to Tesla Service, whatever your individual state of paranoia requires.

    For me so far a: is sufficing, since I mostly stay within a 150 mile radius of home. For Road Tripping it certainly would not hurt to carry a small motorcycle battery in the frunk such as an AGM (leak-proof, all position) $85.00US at any motorcycle/ATV store. Give it a trickle charge once a month. About half the weight of a typical garden tractor battery and it can lay flat in the frunk.
    --
     
  6. Al Sherman

    Al Sherman It's about THIS car.

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    AND c. Something I learned today from the Ranger. It isn't a bad idea to pop the nose cone and put a charger on the 12v pins while installing updates.
     
  7. ChrisgG

    ChrisgG Member

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    how... ermm.. userfriendly
     
  8. Al Sherman

    Al Sherman It's about THIS car.

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    Certainly not required, recommended, or necessary. There have been ten's of thousands of updates installed without this. In my case, I live in the boonies with no 3G and 2 updates in a row have put a smackdown on my 12 volt. Probably overkill but the 12v going down too low during an update hasn't been fun. Except for getting to spend time talking Tesla with my favorite Ranger. :smile:
     
  9. wycolo

    wycolo Active Member

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    > no 3G and 2 updates in a row have put a smackdown on my 12 volt. [Al Sherman]

    Now there's my motivation - to bring out a polarized connection from the (buried) 12v battery into the frunk - before the next upgrade. Good idea!
    --
     
  10. montgom626

    montgom626 Active Member

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    Al, I was under the impression that the 12v was charged by the main battery pack 24x7. Is that not exactly correct?
     
  11. islandbayy

    islandbayy Active Member

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    Well, After digging through my Frunk, replacing the 12v battery with the lithium is not going to be dooable, as how the MS manages that battery.
    Having one as a spare is dooable.

    I have been monitoring my 12v battery, So far mine has been solid, however, I have been monitoring the voltage of that battery for the last month while driving.
    Now, fully charged 12v lead acid battery should read abotu 12.8-13v. The voltage of the battery while the vehicle is in use, has been between 13.6-14.9v. That is VERY high for a AGM or Gel Cell battery, and can cause pre-mature failure.

    Now, I understand their is power being taken from the battery, and I know I cannot tell how many amps are being transferred to the battery so I cannot come to a full conclusion. I have tested the voltages using the terminals behind the nose cone, and am getting the same voltages when the car is parked and idle. That might be part of the battery failure problem as well, though, without more information, of which I cannot easially get, I cannot make a definitive conclusion.
     
  12. montgom626

    montgom626 Active Member

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    Is the 12 volt continuously charged by the main battery pack? Is there ever a time when the 12 volt is not being charged by the main battery pack?
     
  13. islandbayy

    islandbayy Active Member

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    Ive only found a single instance where I was able to check mine under the front nose cone and it was not being charged. Usually, by the time I remember, I have already opened a door or the trunk, and the car has begun a "wake up" cycle of some sort. I am going to try again after work, see what the voltage reads.
     
  14. montgom626

    montgom626 Active Member

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    You are amazing. I would never be able to pull the nose cone or anything else off of my MS. I am mechanically illiterate.
     
  15. islandbayy

    islandbayy Active Member

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    You need to give yourself more credit. You did manage do built that Rally Fighter, even if you were only helping, and you got that sweet setup at home. Though, the nose cones arnt on their the best, with a credit card, one can have it off in a few minutes. I can see it now, "someone stole my nose cone!!!" posts :)
     
  16. Johan

    Johan Took a TSLA bear test. Came back negative.

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    Superglue :)

    Really though, info from this thread and previous threads on this issue has different people come up with similar readings of the battery being taken to very high voltages, way above 14V. The 12V batteries used by Tesla are just regular 12V batteries as far as I have gathered, so I can't really understand why this is going on. We all know it's not good for the battery.
     
  17. Al Sherman

    Al Sherman It's about THIS car.

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    My understanding is that this doesn't happen during update installs. That's when my 12 volt has been drained both times.
     
  18. jeffhre

    jeffhre Member

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    #18 jeffhre, Aug 28, 2013
    Last edited: Aug 28, 2013
    islandbayy - what if you were to use a very small 12v battery just to receive power from the MS battery mgmt line bus, for the sole purpose of charging your Lithium Iron Phosphate replacement? Use the smallest cheapest 12V available as a buffer, and would provide some redundancy if the 12V fails as well. The Li Fe would keep the MS systems alive long enough to replace the small 12V without even a hiccup.
     
  19. Perrin21

    Perrin21 Member

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  20. artsci

    artsci Sponsor

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    That's just a state of mind. The nose cone is easy to remove and it's a good place to start:)
     

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