Tesla High Voltage Battery Pack Information

Removing Modules

The pack is down and out of the car and the lid is off. The next step is removing the modules. You hopefully read your pack with SMT and have some idea where the problem is. Someone going fast and taking shortcuts might go to the acute failure, fix it, and close the pack up without looking at anything else. I've said several times, I'm not a professional with tons of experience, but the two packs I've opened have both had SIGNIFICANT corrosion on multiple BMB boards. If you are a DIY owner working on your own car, you are clinically insane to not take each and every module out, inspect each one top and bottom, inspect every voltage sense wire and especially every BMB for corrosion. There is also a critical modification to do on the bottom plastic shield that Tesla designed and then skipped during assembly you MUST do while you have the chance. All this is detailed in the next section and will take a couple extra hours to do thoroughly and meticulously but I believe it is time well-spent. If you have a v2 pack with a broken sense wire, the same applies. Don't just fix the one brick that had the quadruple failure - check every connection on every module! I promise you will find other issues. You know how much work you have already done to get this far and sealing and reinstalling the pack isn't a trivial amount of additional work either. Why would you not take all the time you can to make sure you don't need to do it again in a few months or next year? Please do this for yourself!

Safety First

Please review the safety protocols discussed on the Home Page and the related links. Also re-familiarize yourself with the routing of the HV bus. You have already taken the fuse out, but that only separates module #8 and #9 from the other 350V. Have your PPE ready and know what tools you will need. Have a plan for where to gently stack your modules. I laid out some cardboard and stacked them 4 high. They MUST have their plastic shields on when stacking. Treat them gently. I strongly recommend marking them with a bit of blue tape as they come out. Technically, it shouldn't matter where they go, but if you are troubleshooting issues, shuffling them like a deck of cards won't help.

Cordless Drill

Never get 'comfortable' working near HV. Proceed cautiously and deliberately. I like to use a cordless drill to loosen the lugs. This allows the important one-hand technique and the drill itself is insulated adding a layer of protection. A real pro would have a magnetic socket for the drill.

Insulated Magnet

If your socket doesn't have a magnet inside, use an insulated magnet to lift the bolt out. Use one hand and lean over the case so you don't make contact with the case with your legs or torso

Coolant

The blue coolant Tesla uses is G48. It is nasty and sticky and corrosive. Even though we removed as much as we could a couple steps ago, you will go through half a roll of shop towels used as diapers to catch all the drips. Stuff them down in the coolant area next to the module when you start working. The nipples are basically 5/16" stainless tubes so you will thank yourself if you get a bunch of rubber caps for that size tubing. You will need 32 caps to plug 16 modules. If you see any G48 present in the pack that isn't just dripping out of the coolant nipples, clean it off the modules immediately and have it be a red flag that you might find a damaged pipe or connection when you pressure test later.

Covers

There is a little shield covering the top of each module that just sets in place. Collect these and put them in a nice stack somewhere safe. They are all the same. The hardest thing about these is remembering them before you install the lid...

Module Order

The fuse is out already so next we are going to 'split' the pack to make the voltages lower and safer.

Remove modules #4 and #13 first.
Next, remove #2 and #15 then #6 and #11. By the time you have those out, the remaining 10 modules in the pack are relatively safe.
Remove the eight remaining modules in the main body of the pack.
Last, remove #9 and finally #8. You will notice 8/9 still have hardware holding them down. Bag and tag these because they are unique. Take LOTS of photos of this area. It is the most complicated to put back correctly later in the process.

In terms of what to 'unhook' first, I recommend coolant, then BMS connection, then the HV lugs for the first 6 modules one at a time. After that, you can streamline the process however it makes sense.

Coolant Connections at the Module

These are a little tedious to work with. They are pretty strong but you don't want to cut or poke a hole in one. You will be happy you got a bag of 5/16" caps to help keep the modules from piddling all over everything as you move them around.

The coolant connectors look like this. You use a pick to gently pry up at the top while releasing the two latching portions on the either side. Practice on the one for module 9 at the top of the hump that is easily accessible so you familiarize yourself with how the mechanism works.

It takes some fiddling to get the coolant connections off the module. I recommend a plastic trim tool fork to push them back off the 5/16" nipple they are on so you don't scratch that nipple and have a leak later. Once they are both off, zip tie them together in an 'X' so both ends are elevated and won't leak as much.

This is what the coolant nipple on the module looks like. You need to make sure the clip on the connector captures the collar when you reassemble. The two little o-rings inside each connector does the sealing.

The BMB Sensor Wire Harness

You can practice with this a little on #1 and #16 before you dive into the middle of the pack at #4. It is a 'squeeze-pull' connector with the squeeze on one side. I use a large pair of needle nose pliers going straight down over the center of the connector. Squeeze firmly enough to unclick the latch and pull straight up. It is pretty easy when you get the hang of it. The photo to the left is for #8 or #9 but you can see the style of latch. There is one connector per module.

HV Lugs

This is the part to be extra cautious about. For removal, I recommend a 13mm socket, a small impact gun and a magnet. Put on your PPE and lean over the pack with the impact gun so you don't touch the pack. You are wearing a giant rubber glove and the drill is insulated. Remove the orange rubber cap - it is just pressed on. Don't touch the side of the pack with your body. Pop the lug off with the drill and use the magnet (presumably with a nice rubber handle plus your High Voltage Glove) to lift the bolt away from the pack. Repeat on the other lug. To be extra safe, you can slide a small plastic shim under one lug from each pair during assembly/disassembly.

You can stack 4 or 5 modules on top of each other but make sure the plastic shields are on. Be very gentle placing them so nothing is cracked or bent.

Removing the Module

The modules themselves, have a frame down each side that sits on the frame rails of the pack case and are located by a pair of pins on one side. They fit nicely together but there really isn't anywhere to grap with your (gloved) fingers. Take a thick flat screwdriver and use it as a prybar between the pack case and the module's frame. The leverage will pop it up pretty easily so try not to let it drop back down. It take a little practice to get under the module but once you are, lift up the outside carefully moving the coolant connections out of the way and the module will lift right out from under the HV connections. Congratuations! You are holding a Tesla battery module!

Repeat 15 times remembering the safety order described above. 4&13, then 2&15 and 6&11, etc.

The Last Two

#8 and #9 have some different connectors so I highly recommend taking a detailed series of pictures so you can remember how they go together. You are doing them last in this process because they are more difficult to work around and the voltage on these terminals is extremely dangerous with the rest of the modules in the pack. You will be installing them first during reassembly. Did I mention to take a LOT of pictures of this area? Bag and tag these items carefully and be ready to refer to your pictures when you are ready to reassemble.

Bus Bars

The large bus bars are the flat white metal pieces. The one that goes to the front of the fuse comes from positive lug of Module #7. The lug at the back of the fuse goes to the Negative of Module #8. #9's Positive is hidden in this photo but it goes all the way back to the contactor at the back of the pack.

8/9 Bar

This strap ties Module #8's Positive to Module #9's Negative. Remember #9 is upside down so the + of #8 is right below the - of #9.

90* Bracket

The 8 and 9 Modules are identical to the rest but they need some extra hardware because of their orientation in the penthouse. Tip: You don't need to remove this one to do the basic repairs but be careful the post doesn't make contact with the wrong thing.

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