Opening the Pack 

Overview

Once the pack is on the rollers, what do you do with it?  If you are repairing a failure inside, you need to open the lid.  This part is significantly more difficult than dropping the pack and is also significantly more dangerous.  Make sure you have reviewed all of the safety information from the Home Page.  Have your PPE ready and fully understand the HV bus from the Basic Architecture material.  If your pack had any isolation faults, it becomes especially important to be meticulous about your PPE through this entire process.  The lid is glued down with a couple tubes of really strong sealant and what seems like a million little Torx and 8mm bolts.  There is also a large plastic sheet on the top covering many of those bolts with a ring of butyl tape you need to remove without cutting or damaging the plastic sheet and a blanket under the sheet.  Opening the pack is a LOT - a big commitment, so please take time to assess your skills and risk tolerance before you go further.

The Plastic Sheet

Depending on the life your pack has lived, the butyl tape might need to be cut or it might peel off easily.  Don't worry about trying to save the butyl to reuse.  A $15 roll from Amazon is generally available for overnight shipping and a 30' roll will give you all you need with a little left over.  Pro-tip to get any sticky stuff off the plastic - put it in the freezer.  Be careful not to cut or stretch the sheet.  You need to be able to reuse it later and like most of things related to the pack, you can't get it from Tesla.  The insulating blanket can be folded up and set aside.

Pressure Test

I highly recommend doing a pressure test before opening the pack (but after the plastic sheet is removed.  The process is detailed on Tesla's Service Page .  They say that more than .2 psi (yes, 20% of one pound per square inch) will damage the pack but really, any more air pressure will just blow out the umbrella valves.  That said, you need to source a regulator and gauge that can read down that low.  The umbrella valves will likely leak a bit anyway so the best value you will get from the leak test is to find bubbles.  Mix some water in a spray bottle with a couple squirts of liquid dish detergent.  Apply air pressure to the pack through the test port at the back left and squirt every seam and bolt head.  Make sure you cover the rapidmate connections at the back with some tape before you start so they stay dry.  Chances are good you will get some bubbles.  Remember, you can can get bubbles on a seam or at a bolt head.  Make note of those so you can look for signs of liquid water inside.  We will revisit the pressure test and spend a lot more time getting it perfect when everything is getting sealed back up. 

Major Water Intrusion

If you can't do a pressure test because the fuse cover has an obvious hole in it and your car shut off because of a BMS_f123 internal isolation error, remember that your pack is very dangerous.  The water sitting inside the pack is making an electrical connection between two or more metal pieces where there should be complete isolation.  You don't know where the electricity is sitting ready to zap you.  Be extra cautions.  The first thing to do with a 'wet' pack is remove all the umbrella valves and tip the pack side to side to see if any liquid water will drain out.  You will still have a lot of work to do to clean this up, but removing all the standing water you can is a good place to start.

Fuse Cover

Most information will tell you to open the fuse cover and remove the fuse before you start but we learned in the pack architecture section, the fuse does very little to make the pack 'safer' to people working on it unless there is an unlikely failure with a contactor.  Since you are removing the penthouse cover anyway, it is easier to remove the fuse cover from the penthouse after it is removed from the pack.  There is a collar riv-nutted around the opening.  When you start trying to pry the cover off, make sure you don't pry under the collar.  Once the penthouse is out of the way, use your PPE and CAREFULLY remove the fuse.

Important Safety Note

You do need to remove the fuse once it is accessible after the penthouse cover is off because working around the contactors at the back of the pack is much more dangerous if the fuse is in place and you will be opening the lid back there later in the process.

The Penthouse

The most tedious parts of opening the pack involve cutting the generous quantities of sealant used in the assembly process and the penthouse has plenty of it.  After the plastic sheet and blanket are off and the pressure test is done, the penthouse is the first big thing to remove.  Remove all the fasteners.  Bag and tag everything.  Don't count on remembering where they all go when you are ready to reassemble.  The 4 tiny security screws around the coolant rapidmate are the same head as the fuse cover.  The majority of the penthouse can be cut free with a small putty knife and a small mallet tapping away.  You must be cautious to not pound the blade too far into the pack.  The knife is metal and there is a lot of energy inside.  The modules under the penthouse are #8 and #9.  Although the penthouse cover is the first part of the cover to come off, modules 8/9 under it are the LAST modules to remove for safety reasons (and the first to go in for reassembly).  More on that later.

Once you have the penthouse loose, it is likely the coolant rapidmate is still sealed in from the underside.  See the picture below about popping that free without breaking anything.

The BIG Lid

Your next step is to remove all the fasteners on the lid with the exception of the fasteners around the rapidmate cover.  The fasteners the attach the big lid come out, but not the ones on the silver rapidmate cover at the very back of the pack.  Once again, bag and tag everything.  Many bolts are identical but some are slightly different lengths and you don't want to have a long and short one in the wrong place later.  Again, pleave the fasteners around the back side of the rear rapidmate cover for now - just remove the ones that the lid is attached to across the front of the rapidmate cover.  The bolts along the rapidmate are some of the ones that are a different length so pay attention.

There are also 3  bolts holding a bracket down at the front.  Remove those but don't worry about separating the bracket yet.

Cutting the glue is a pretty awful task but it has been made easier by some recent technique.   A specific shout-out to Facebook contributor Ron Timmons for sharing his 'pull through angle-iron' method.  The material in the photos below is a piece of 1/8" thick aluminum angle iron 3/4" by 3/4".  You don't want deeper than the 3/4"  because it could contact the coolant tubes for the modules.  Drill a hole in the end when you can snake a coat hanger through to attach the hook of your winch, ratchet strap or come-along and whack it with a hammer to flatten it out slightly.  Use a putty knife to break a little bit of the glue at the end and tap the angle iron in a couple inches to get it started.  Now pull it through until it comes out the other end.  In the 4th image  below, you will see we got creative using some 2x4 to block again the solid object where the winch was attached.  Drill another hole on the opposite side and repeat the process on the other side of the pack.  You see the 'flattened' look in the 4th image below.  It doesn't go in easily at a perfect 90*.

The Big Lid Continued

At this point the front and sides should be pretty much cut free.  You can take your angle iron and pull it across the glue between the rapidmate plate and the lid at the rear of the pack.  The first image below shows the area with the lid already removed.  As mentioned, the rapidmate plate itself can stay in place unless you need to work on the contactors so don't remove those fasteners and don't cut the adhesive around the back of the pack.  Now the entire perimeter should be loose.  Get a helper to lift up on each side one at a time.  You need to break to black metal 'ribs' loose that are used to hold down the modules.  You will feel them release.  Be careful to not cut yourself or bend the lid.  When you have both sides lifted, you are ready for the most challenging part of the process - The Center Spine.

Most professionals tout the 'butterfly' method where they essentially fold the lid up leaving the center glued down.  I'm certainly not a professional, but I can see the appeal - it would save a lot of time.  As a DIYer, however, I put a MUCH higher value on completeness in terms of cleanup, and the ability to carefully prep and prepare for reassembly.  I'm also not crazy about folding a piece of metal and then flattening it out again.  Metal fatigues and you can't do that too many times before it starts to tear.  I choose to have the lid come all the way off...

The Wedgie

You can see a few of the details of the center spine below.  The orange caps are covering the high voltage lugs and even though the fuse is removed, you certainly don't want to bang a metal cutting tool down the center.  The good news, however, is that the frame of the pack's spine is at a higher elevation than the HV or the BMB control wire harnesses.  I have done this precisely twice so your mileage may vary but here is the basic process:

1. Take a 2x4 approximately 3 feet long and cut it diagonally making two wedges.  The wedges in the first image below are a little too short and abrupt but you also don't want it too long because the sharp end is too thin and weak if the wedge is too long.

2. Starting at the back of the pack, get the wedge started down the center between the frame and the lid.  Be careful the tip doesn't go under the frame where it starts.  You can use the extra wedge to try to lift it up slightly from the side.  This is shown somewhat in the 3rd picture below.  I believe this was Ron's image and he is using some sort of non-conductive plastic wedge.  I'm sure there are better tools out there than a scrap of 2x4...

3. Once you get the wedge started, tap slowly with a heavy mallet, moving the wedge forward down the center.  Have a helper watch the progress from the side to make sure you don't snag or run into anything you shouldn't.  Slow and steady.  The 2x4 is 1.5" wide which is about the spacing between the black ribs attached to the lid.  They help keep everything centered.  I suspect the wedge is moving 1/8" per tap.

4. When you reach the end of the wedge, use a scrap piece of 2x4 (i.e. the other 5 feet that didn't get cut into wedges) and continue tapping.  When you get down near the hump, you should be able to tell when the lid is free and lift it off with a helper.

Hopefully, the lid is off and mostly flat with very few creases and ripples.  The black ribs that went between each module are glued in place and we will be removing them to clean the surfaces in the re-sealing section.  For now, stash the lid somewhere safe.  The edges can be sharp so they like to scratch paint, cut helpers and most importantly, fall onto HV components at the worst time.  I found that standing it up against some shelving worked and I used a zip tie through a bolt hole to keep it from falling.