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Battery Tender?

Discussion in 'Model S: Battery & Charging' started by darthvdr, Jul 25, 2013.

  1. darthvdr

    darthvdr Member

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    I recall reading on this forum that the 12V battery will go low if the vehicle is not driven for an extended period of time. I am doing a family trip in a couple weeks and would like to know what battery tender brand are you using. TIA
     
  2. mnx

    mnx 2013 P85

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    I hadn't heard that. FWIW I've left my car for 1.5-2 weeks without issue....

    I got a Noco Genius tender/charger for our minivan since it sits around a lot since the Model S has arrived.
     
  3. Merrill

    Merrill Active Member

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    I use the Battery Tender Plus from the Deltran corp. on line from Amazon. Using it on our ML430 since it sits around a lot.
     
  4. darthvdr

    darthvdr Member

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    What setting is advised in terms of amperage? I will be taking a 3 week long vacation, so I just want to make sure the battery is maintained. Thank you all for responding.
     
  5. spaghetti

    spaghetti Member

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    I have used a CTEK 7002 on my BMWs for quite a while now. Love it. See CTEK Multi US 7002 12V Battery Charger : Amazon.com : Automotive
     
  6. Cosmacelf

    Cosmacelf Active Member

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    My understanding is that as long as the main battery pack has juice, the car will use the main battery pack to keep the 12v battery charged. This allows you to park the car unplugged for a week or two (for now, bearing in mind vampire losses until the vampire loss release comes out).
     
  7. montgom626

    montgom626 Active Member

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    I don't think so. I think that the 12 volt is not charged by the main battery unless the car is on. The 12 volt can be discharged if the car is not on for extended periods of time if the car is not on and not plugged in. Anyone know that not to be the case? The main pack is "isolated" from the 12 volt unless the car is on.

    - - - Updated - - -

    That is my understanding too.
     
  8. brianman

    brianman Burrito Founder

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    My understanding is slightly different from yours.

    I'll try to nutshell it.
    1. Tesla firmware has some minimum voltage that it considers acceptable for the 12V.
    2. Tesla firmware has some minimum energy that it considers acceptable for the main battery pack.
    3. If the 12V is below its minimum and the main battery pack is above its minimum, the 12V is replenished from the main battery pack. The "On"/"Off" state of the car is irrelevant.
    4. If the main battery pack is below its minimum, it goes into self-protection mode and no longer cares about helping the 12V.
    5. If both batteries are below their minimum (and thus the 12V stays "stuck" below its minimum), things get... problematic but not immediately. Somewhere a bit below the "main to 12V" trickle minimum, the 17" becomes unresponsive. You can no longer open the charge port or put the car into neutral. The disabling of both of these features is a perfect storm of "screwed" because you're basically force to flatbed it "improperly".
    6. A jump pack (but ideally a stronger source like a running vehicle) can wake up the 12V long enough to get it to open the charge port and negotiate with a charging station so that it can wake itself back up fully.
     
  9. dtich

    dtich #P708

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    yes. this is what i understand as well. fairly exactly.
     
  10. Gear

    Gear Member

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    Good to hear. I was worried I'd have to hook a battery tender up to the car while I'm away on business. Glad to hear I can just leave it plugged in and set at a low SOC while I'm gone and it will take care of the 12v battery itself.
     

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