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steps to pull 12v battery ?

Discussion in 'Model S: Battery & Charging' started by scottm, Sep 30, 2017.

  1. scottm

    scottm Active Member

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    I'm changing front upper suspension arms and in order to do passenger (right) side, the 12v battery has to come out to make a space allowance for a suspension bolt to slide out.

    This is a 2014 RWD car, so it's got the nose-cone, pre-facelift, with the 12v battery in a very awkward spot.

    I've got the car stripped down and now staring at the top of a 12v battery with all kinds of connections on it. I've removed the two battery strap bolts.

    What are the steps to safely pull it? I recall seeing a thread or a how-to posted by a guy who video documented this .. but can't that now, of course.

    I tried this: open windows and hatch, frunk up, driver door remains open, do a "power off the car" on the console and get the "are you sure?" hit the yes button and everything seemingly dies...

    OK, great, but when I was then removing the negative terminal connection on the 12v battery post, a few sparks tells me the car was not dead-dead powered off, and then began coming back to life. Things whirring and clicking in frunk area where I'm working, console on bright and happy... crap.

    Is there a "master fuse" or switch to pull or disconnect before disconnecting the 12v neg terminal?

    Need to know the sequence to pull the 12v correctly.

    (Help! in middle of job and this wasn't supposed to take all day -- storm coming tonight and wanna get done!)
     
  2. jplasmd

    jplasmd Member

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    I replaced my 12v battery on a 2014 P85 earlier this year. Pull the negative first, then the positive. The service manual mentions waiting two minutes to allow everything to discharge, without giving any more info. Don't forget to leave your driver side window down so you can open the car. Probably best to lower the other windows also. If they are left in the full up position, you could potentially crack the glass by closing the door.
     
  3. boaterva

    boaterva Supporting Member

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    Maybe too late now but here’s the video on how to do it.

     
  4. scottm

    scottm Active Member

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    #4 scottm, Oct 1, 2017
    Last edited: Oct 1, 2017
    Still timely, thanks... that video series was what I saw before, thanks!

    I got the car moved into a garage and called it a day .. so going back at it today to finish the job.

    I was able to go from that Part1 video you attached (all about the battery) and found Part2 (which is the work of replacing).

    Part2




    Here's a key shot from that video ... showing (blue boxes) bolts to undo on the tray sitting on top of the battery.
    Capture.PNG

    I don't think he makes any mention in the video of undoing the negative terminal first, before going at those hot bolts with a ratchet... but here you can see that negative clamp is off and away from the battery, moved to the side. Personally, I will cover the negative cable and post with something insulative because I wouldn't want a dropped tool bridging anything on top of this puppy!

    Also, no mention of any fuse pulling or master switch. After doing a "power off car" from the console, it's just yank the negative terminal.

    He mentions the "power off car" shuts down 3 computers: IC, center stack, and bridge computer... Which kind of answers why several things on the car still seem to work after doing a power off... it doesn't power everything off.
     
  5. boaterva

    boaterva Supporting Member

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    Well, it’s powered off but not really as you can restart it via the brake pedal. So the car isn’t off off.

    I think it’s off enough to pull the battery connections. And you definitely want to insulate connections when you do pull them off. A crowbar short is the last thing you want to happen since you still have the HVB connected (unless you’ve pulled the emergency loop).
     
  6. scottm

    scottm Active Member

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    #6 scottm, Oct 2, 2017
    Last edited: Oct 2, 2017
    OK ... new suspension arms are in, car drives like on rails again.

    MAJOR LEARNING about 12v Battery nuts and bolts.
    Do not do what I did by mixing up a couple nuts, as shown, green circles.

    The part 3 video (re-installing battery) makes no mention of this gotcha!

    Capture.PNG

    Although the video mentions 12mm... it actually takes a 13mm to get these two off of my car.

    The two nuts are CONFUSINGLY SIMILAR but one (on the 225A fuse) is metric - it is a 13mm on my car, the other nut (near + battery post) is standard, it's actually a 1/2" nut. A 13mm also fits well enough to take it off. This is why I made my fatal mistake.. thinking they were both metric.

    Thread pitches are so similar on both, you will get a couple starter turns of either nut on either stud that you happen to mount them back onto.

    I thought, OK, this is a little snug but snug is good on hefty electrical connections like these two. So I put a little more hand torque into it. And then the bolt I'm fastening onto (upper green circle) gives way before things are tightened down and just starts rotating with the nut. Yes F#$(@K !!

    The bolt is moulded into this plastic tray.. so I had to get creative and do plastic surgery on the tray, and find/make a new bolt that I could use in it's place, because that one is now cross-threaded beyond cleanup with tap and die... and I had to back the nut off it to get the parts off it... Vise grips were essential in pinching the top of the bolt as I backed off the nut..

    This repair job saga is another thread in itself, but suffice to say, it's possible to recover and get road bound again.. Start by buying a good ol' battery post clamp replacement part from an autoparts store. Grab the bolt off it. It has a SQUARE head and fits from the bottom of this plastic tray into a square channel moulded for that OE bolt... The problem with the OE bolt is that its square little head is only about 1/16" thick, and as I found out, doesn't take much to start it spinning - cuts its way around within its plastic channel. The channel has enough depth to hold a bolt head that is about 1/4" thick... so the undamaged part of the channel offers enough square meat to hold the head while you're doing the tightening from the top side again with the nut.

    BOTTOM LINE here... Tesla may change out parts from car to car from time to time.. And they're not afraid to use metric and standard nearby each other on the same part (battery top tray).
     
    • Informative x 3
  7. scottm

    scottm Active Member

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    Nother tid bit..

    The yellow circled bolt holds a battery post onto the battery.

    You do not need to take the negative post off the battery. Leave it on.

    Just loosen the nut on the battery clamp that you see pushed off to the lower left side of this picture, that's enough to pull the terminal off the post.

    Pulling this terminal is the event that completely depowers your car. My door handles were mid-flight (half way presenting) for some reason, when they stopped as I pulled the terminal, and they stayed there for the duration of the project until battery reconnect.


    Capture (1).PNG
     
  8. scottm

    scottm Active Member

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    Another observation...

    I had the rear power hatch up on the car during this work... as a means of getting into / out of the car if I needed to. Didn't need to.

    But when the car was all ready to go again... the remote hatch button and the button on the hatch itself failed to close the hatch. Just BEEP BEEP BEEP.. no budge. The car refused to acknowledge it was allowed to move the hatch again.

    So, I close the hatch manually by pushing it down gently until the latch caught it and power-pulled the latch shut.

    From then on, hatch has worked again as it should responding to buttons.
     
  9. scottm

    scottm Active Member

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    Here you can see (on the left) the Tesla stud that is molded into the plastic tray for holding the one end of the 225A fuse and heavy lug for heavy cable going to battery. It has a very thin square head on it, meaning very little to hold it from spinning.

    On the right is a pretty typical stainless steel bolt with hex head to show what a normal head thickness would be. This is not the bolt I used for the repair. I used a square-head bolt off a battery terminal clamp.

    What's shown in the middle is a square nut that I bought at Lowes hardware. I actually used the square-head bolt mentioned plus this square nut spun on tight to the head of that bolt - then reduced a bit on a grinder ... to make the maximum square head thickness that would fit in the plastic square channel.

    IMG_20171006_134915.jpg
     
  10. boaterva

    boaterva Supporting Member

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    Stupid question... isn't the spline on the left one supposed to be what stops it from spinning? Or did/has that broken loose so you need something else (thicker) to be able to grab onto?
     
  11. scottm

    scottm Active Member

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    I would say it's a combination of the spline and the shape of the head that are meant to stop it from spinning. No way could the spline alone stop it from spinning for the decent and proper amount of torque on that nut needed to make good electrical contact of components mounted to it.

    This bolt is inserted in from the bottom of the tray into a square channel. The spline is either hot molded or maybe cold pressed into the plastic and has a definite purpose of simply holding that bolt in place on the plastic tray for assembly purposes, probably similar for all the other studs on the tray so they don't go thunk and fall out when the tray is flipped over and placed over the battery to have all the things attached to them.

    It's informative to point out... this troublesome bolt has an "access cover" on the bottom of the tray that can be peeled back so the bolt can be pushed out that way. So I was "lucky" I screwed up this one. I think other bolts on the tray don't have this bottom access and are hot molded in as "one piece with the tray" and if they started to spin from over tightening... probably new tray time.
     
  12. RScottyL

    RScottyL Member

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    Did you decide to keep your current battery (3 years old), or go ahead and replace with a new one?
     
  13. scottm

    scottm Active Member

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    #13 scottm, Oct 14, 2017 at 8:31 PM
    Last edited: Oct 14, 2017 at 8:39 PM
    Since I keep real good care of my 12v battery... I did not replace it

    Starting in year 2 of ownership
    • I keep a 12v battery minder (Ctek) connected while parked in my garage at home, all the time... prevents needless cycling.. also side benefit of holding main pack charge level because there's no 12v recharging going on from the main pack
    • At work, I charge the car using 120V outlet and UMC... the car never reaches the set point because charging is so slow... but there's no 12v cycling going on either, because contactors keep closed while UMC charging and therefore dc-to-dc is available for 12v service (instead of draining 12v battery)
    • and of course, while driving my commute both ways there is no 12v cycling because dc-to-dc is keeping the accessories going
    Pretty much baby that thing... the 12v battery may last the life of the car if I keep this up! (I hope I didn't just jinx myself)

    At least now I know how to replace it, if/when it needs it. After having reached it to pull it out once it's always easier second time going in.
     

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