VW Beetle Conversion

Last updated:11/26/2021 3:44 PM PST
VW Bug conversion to electric


SHIFT EV is converting this 1970 VW beetle to electric power for a couple from Washington state.

Design goals:

  • Desired range: 150-200 miles from fully charged.
  • Acceleration: Better than stock
  • Instrumentation: Stock speedometer, fuel gauge to display correct State Of Charge (SOC).
  • Charging: SAEJ1772 Level 1&2 (110VAC and 220VAC)
  • Heat: PTC (electric) heater, Operated by stock heater controls

Evaluating battery type and capacity we have to consider the energy consumption rate for typical driving. Many bugs have been converted in the past with efficiency claims between 200 and 300 Watt-hour per mile (Wh/mi). Many variables contribute to this efficiency such as weight, tire type, motor efficiency, speed, etc. To determine battery capacity we'll take the upper and lower end of our range goal, and multiply them by 250Wh/mile.

(250Wh/mi) x (150 miles) = capacity of 37,500Wh, or 37.5kWh

(250Wh/mi) x (200 miles) = capacity of 50,000Wh, or 50kWh

With target battery capacity understood, we then look at available motor and controller/inverter solutions that provide good efficiency and power per dollar for this application. We narrowed it down to either an HPEVS ACXX or one of the NetGain Hyper9's. Ultimately settling on the Hyper9. That locks us into a maximum and minimum voltage range that our batteries must provide.


Tesla S or X Battery Module

After reviewing a few types of batteries in different scenarios, the Tesla battery modules used in the Tesla Model S and X are a good option for this build in several ways.


  • Slightly used Tesla S and X battery modules are 5.2kWh (depending on some model variants). 5.2kWh x 10 modules = 52kWh of capacity. That's 2kWh more than we'll need.
  • They have a high energy density, meaning they're more compact relative to many other batteries.
  • They're capable of more than enough power that our system will draw 750A.
  • As long as healthy modules are purchased, they're a good value at around $230/kWh on today's market.
  • We can accomplish our drive systems maximum and minimum voltage range
  • With 5 modules wired in series, the full and empty voltages fall within the operating range of our motor controller. To use all 10, we'll run two strings of 5 modules this way, in parallel. During discharge, one string will its + and (-) outputs in parallel with the other string. To avoid hazards is critical to have a BMS that properly monitors and manages the two strings and decides whether each string is allowed to connect the DC output bus that is used by the motor controller or any other loads. For more on this surprisingly complex topic, start with this document by Orion BMS.

With the high-level system decisions finished, we move into how we're going to properly and elegantly fit and wire these parts in the space we have. Beginning with the battery pack spaces.

Adjustable test fit jig for battery box concept
Mockup of a proposed battery box design, to confirm fit of the complex battery box shape.


Front view of SHIFT EV's 5module VW battery box -front
Front box in place. Fitting the stock-sized spare tire is a bonus.

SHIFT EV 5module VW battery box - rear
Five-Module battery box for the rear.


SHIFT EV's 5module battery box - rear-2
Five module battery box resting in place. It will move rearward a bit more on final assembly.

Preparing parts for powder coat


Opening Tesla battery pack to remove modules.


Modules exposed.


Modules extracted, stacked on a pallet behind the empty battery tray.


Some other useful parts are recovered from the Tesla pack, but most of it (metals) goes to our local recycler. 


10 Tesla S modules will go into the beetle (16 modules are pictured).

This week we worked out the specific placement of components that are not mounting directly to the battery enclosures. To do this quickly, we took measurements and printed off several sheets of the orthogonal views above, and begin sketching out scenarios.

A bit of non-EV conversion effort is occasional restoration work. The thick dirt had built up over decades. The painters didn't remove the heat and sound deadening material, so underneath lies a bit of clean-up. This clean-up was made sense to do now because wiring and access will be difficult after the conversion.

These tail-light grounding connections were previously corroded due to being buried under dirt (mud in winter). Also, you can see the engine rubber seal bits that were left have been cut off clean at the gasket attachment point. Once we know how we want to seal up the final engine bay, we'll see if we need to remove that bead or finish things in a better way.

Another shot shows the blue paint on the otherwise black rubber engine bay seal. What's left of it.

The Engine bay cleaned up. transmission adapter plate fit-tested, and ready to receive the motor (which hasn't arrived yet).

Other things worked on:

  • Updates to wiring diagram to reflect this build.
  • Located all non labeled wires (16) and isolated them with tape for a 12v power-up test. They'll need to be traced and decide what to do with them later.
  • Powered up 12v systems & verified what works:
    • horn
    • brake lights
    • turn signals
    • headlights
    • headlight dimmer switch
    • speedometer light
  • windshield wipers
    • What didn't work:
    • dome light (switch)
    • glove box light not working
    • didn't check courtesy light switches (door switches), hood light, trunk light, or license plate light.

      The charge inlet is installed in the stock fuel location. It was a bit of work to trim out the old gas tube and weld in the backing plate deep enough for the inlet to not block the original fuel door. It's a nice subtle finish and accepts large J1772 connectors.
      The motor, controller/inverter and wiring harness arrived and we've installed the shaft coupler and the trans adapter plate. It is staged for the KEP performance clutch, pressure plate, lightened flywheel, and related small parts that arrive next week.

      This is the fuel display tester driving your stock fuel gauge. The circuit cycles the needle from empty to full to be sure it works, and to verify how we need to build the circuit for the BMS to send proper State Of Charge (SOC) signals to it.

      The rear battery box is powder coated and sitting in place without batteries.

      The front battery box is powder coated and sitting in place without batteries.
      Wiring schematics are being updated for your motor and controller. Once that is done (enough), we will begin pulling the wiring for most components through the chassis. Chris has already been studying and preparing for the best routes on this build.

      Since the last post, the high voltage cables have been pulled from the front to the rear.

      The sound/heat deadening matt was removed from the trunk because we need to mount some parts to the steel wall in the trunk (plus it just didn't look good).  It will look a bit like we're going backward for a few days, but the new finish plan will be much better. Next week you'll begin to see why.

      The upper-left image was after Chris installed the shaft adapter so that it can accept the new lightened flywheel. It's browned because it must be heated to about 400F to expand and slip onto the motror shaft. It cools to a zero clearance fit.

      The lightened flywheel was even further lightened because I couldn't resist cutting off the ring gear that your old electric starter motor will never engage with. Removing this took two pounds off. Doing this will not have a detectable affect on balance.

      Other things done included sorting out the trunk's old wiring and pulling many out that will not be used. Also, fuel lines and emissions parts, and tubing was removed. Space was made under the hood to mount the charger by re-aligning the right front brake line. The holes for the DC-DC (on the front battery box) were tapped for assembly. Next week we begin assembly of the modules into the boxes.

      New Flywheel assembly, a KEP Stage II pressure plate, and a four puck clutch on a lightened flywheel - plus starter ring gear removed.

      Completely controlled by wire, the charger was mounted in the old fuel compartment space. All of its connectors extend to the drivers' side for easy access.

      With the motor installed, the clearance behind it looks good. It is hard to imagine that the engine compartment was barely long enough to get this assembly into place. The motor had to be staged at the proper angle as the car was lowered down over it to get the motor/clutch assembly started around the transmission input shaft. The motor was simultaneously inched forward to clear the rear body panel. For much of this maneuvering, there was less than a 1/4" of clearance between the body and the motor until the splined transmission shaft lined up with the splined hole in the motor coupler. Then the motor assembly slid forward over the transmission shaft and stoped against the adapter plate. Notice 1 of 3 bolts is missing from the back of the motor on the middle photo. That's because there wasn't enough clearance between that bolt and the body.

      These images show the front box in position with the DC-DC converter, BMS, and main contactor with a high voltage fuse. We are verifying fit, final wire routing, and service access before the final installation of the battery modules into the box. Re-routing of some under-box wires and the hood-release cable were things we knew were needed. We also decided the 12V fuse panel will be relocated so that its backside wire connections can be accessible in the future for serviceability.  I didn't get an image of the template and location yet, but I'll post it next week.

      The 12V fuse planel landed here. Easy to reach and still in the standard VW configuration. There will be other cosmetic panels covering up the less than pretty backside of the dash that is normally exposed. 

      This was a super short work week for me and the crew, so there's not much visually to show. However, I have a question for you to think about over the weekend. I realize interior work was to follow the conversion project. However the dash is in pretty rough shape as seen below. It can only be removed with the battery box out of the way. The box can be removed by the other interior restoration folks, but I'm wondering if you would rather have the issues below addressed now? This will avoid having someone else pull that pack for access later.

      And finally, I have a suprise that is 16% bigger. Bigger than what you ask? Bigger capacity, of course. I recently bought TESLA battery modules from a Tesla P100D. Thes have more cells in each of the same sized modules. Externally, only the coolant plumbing is a little different. Otherwise the same external dimensions. They came from a Tesla that was purchased for reverse engineering by a TESLA competitor. The car wasn't wrecked and had been driven less than 5000km. I would like to mount these into your Beetle instead of the P85 pack above. I hope you're excited about that.

      The images above show the rear battery box coming together. The top-left and the two bottom-right images show the box sitting upright. The rest show the box tipped on it's back while making a revision. The base bolt holes (originally slots) were where we planned to bolt the box to the floor. The revision is the addition of the rivet-nuts being fitted and fastened to teh base. This will ease assembly, reduce parts and be a bit more strong.

      To install the new BMS, we need to wire the new cell tap wiring harness and cell temperature wiring harness to each battery module. We must replace the stock PCB (green) with a reliable connection method. The stock PCB precisely positioned the cell tap connectors (red) to minimize movement and stress on the connecting flex circuits (blue/orange) coming from the cells. The white connection mates to the new BMS cell temperature harness. Its position is more flexible. The black connector is where the Tesla wiring harness was to connect to the module.

      Top left & right are the first draft of a 3D model and its 3D print process set-up. That draft was used to quickly check for interferences when in position on the module. The bottom left and right images show the latest 3D model and printed part with connectors in place. The channel guides keep wiring organized and the small slots are for zip ties to secure the wiring. In the past, we have installed aftermarket PCBs (not pictured) sold for this purpose, but they would cost >$300 for this 10 module pack and require more labor time to install because of connector issues of their own. The 3D printed solution cost is $0.50 each, which eliminates the need for the black 10 pin connector and allows visual confirmation that connectors are properly seated without removing the fixture.

      The old dash panels, switches, glove box door, etc. have been removed.

      Much of lasts week was spent researching the best PTC components to assemble at least a 1.5kW heater system that will fit in the available spaces without crowding the passenger compartment. Most heater system parts have been ordered. The under-the-hood ductwork will be ordered when we see what parts and shapes we need to mate to on the dash kit ducts.

      Wheels are in! We didn't make them, but it's always nice when big shiny parts arrive for a project.

      The tires are mounted on the wheels with chrome valve stems and caps. this will look really nice when they go on the car next week.

      This week I uncrated all the Tesla P100D modules. I'll spare you the booring images of that process.

      The rear battery box is bolted together except for the side walls. Modules were inserted, and the fit was as good as we had hoped. BMS cell taps and temperature wiring is underway. Then we'll make the high current series cables and install them between modules. The final steps will be plumbing, leak testing, and cell tap harness testing.

      This image shows the black 3D printed board using scavenged connectors from a TESLA slave board. The green board is a TESLA slave board (which we don't need) that we are testing the idea of using its connectors without removing them. We're looking for the most stable way to make our connections considering serviceability, visual inspectability that connections are seated completely and a few other things.

      Dash parts and stereo are ordered.

      I've been working on various ways we plumb in a great (3kW+) heater and defrost system. Upper left is a 1.5kW 6 element PTC unit. That's like what is inside the black assembly pictured. The gray assembly is smaller, uses nichrome elements much like a hairdryer, and multiple units can be located where needed much like a hairdryer. All types have pros and cons. At the bottom are the missing VW defrost ducts that just arrived.

      The new wheels are on and looking good.

      The cell taps and thermistors for the front battery box modules are wired. The tester shown checks for proper pin-out of all connections and wire issues when we giggle the harness. It's a life saver. Next, we'll train the wire looms into position and start making the high current series connections between modules.

      The engine compartment was cleaned up more (removed all the spray-glue), oil. Then wire brushed and sanded the rust off. Masked and painted. The wiring cleaned up nicely as well. The BMS mount holes were drilled and revet-nuts inserted. Next, we'll mount the high current fuse and contactor (from the rear battery) and the motor controller and fluid cooling systems. Lower panels will be formed to help keep the weather out.

      I know this diagram isn't readable, but it gives you an idea of how we've laid out the component wiring diagram in a way that shows component location and wire routing between different sections of the car. This is one of many tabs from the wiring diagram drawing set.

      This image shows the motor controller/inverter in position. Since this image was captured, I've updated the coolant portions of the wiring diagram to show pumps, radiators, plumbing and ordered the parts to make visually appealing connections to the two chiller plate ports visible at the top of the controller/inverter box. Also not shown, are the stand-offs that hold the inverter/controller 1/4" off the firewall that it's mounted to.

      As discussed before, the new tires are slightly wider than stock. Because of that, we discovered that the spare tire doesn't quite fit into the stock VW space. So we'll be exchanging your spare for a slightly narrower tire.

      The dash parts arrived, except they forgot to ship the main large part. I reached out to the vendor and they've responded positively. It should arrive early next week. We haven't received the stereo parts yet.

      This was a busy but unproductive week at the shop. One day was spent preparing for the film crew for the pilot called "EV Rides" and the following two days were spend with them at the shop and out getting moving shots with past customer projects. Without air conditioning, it was above 90 degrees in the shop so not much happened there this week. The film crew was interested in your car and recorded some video, but the story they have in mind seemed to focus on finished cars, so I don't know if they'll feature shots of your car or not. They said it would be a couple of weeks before they publish. If there are scenes using your car, I'll post the video here for you when it releases.

      High current cables were started, and cooling systems parts were gathered and began getting mounted and plumbed. The wiring diagram was updated to consolidate low voltage fuses and reduce wire runs between sections of the car. In that process, I determined there are 10+ EV related low voltage fuses and at least 4 relays all in the engine compartment. Rather than add in-line fuses, we're adding an additional small fuse block in the engine compartment that will look neat with a nice cover. The stereo and final dash replacement piece has arrived. I'd have more images to show here but I'm having trouble recovering them from my phone.
      As we commit to more part locations & circuit routes, I've ordered a lot of small parts like plumbing fittings, relays, sealed High Voltage (HV) box, fuse blocks, etc. Also, more refinements to the wiring diagrams. This is normal at this stage.

      The big box of goodies from the Stereo order turned out to be missing the radio unit. I spoke with the vendor and they knew it, and said it's on backorder and should ship in 1 to two weeks. I'm a little bummed because we wanted to get that dash in before the front battery box is complete.

      The P100D battery modules are missing some plumbing fittings and some of the plastic clamshells that protect them. The seller didn't specify that they "were" included. It is just standard protocol and I made an assumption. I'm working to source those parts. We have enough to assemble the rear battery enclosure and that is now wired and the other end (plumbing) will begin Monday. I expect to have that battery pack in the car early next week.

      The heater has been challenging. I've purchased several different types of heater units that I thought might be slick for the limited space. I'm not satisfied with any of them being under your hood and then plumbing big vents through the wall above your knees. You won't be billed for the heater systems not used, they'll be perfect for another build sooner or later.

      The best heater plan for your car and in your climate appears to be mounting it in a console (to be purchased as seen above, or something similar fabricated) over the hump between the driver and passenger knee-space. That will get you the heat directly and efficiently, and one or two well-hidden tubes can be routed to the windshield defrost. A console like this offers a clean way to add the fan controls. You're probably aware there was no electric fan in the stock VW's because pressurized air from the engine cowl/fan was used. The stock controls were only valves opened by cables. Please let me know if you would like to discuss this further, otherwise, I'll keep working on that plan.

      This may bore you, it's an image of the rear battery box cables being cut, crimped, and the protective heat-shrink tube added (black) to the connectors.

      This image shows the high current cables (orange) and cell tap/thermister harness installed. The cell tap wires (small red, yellow, orange) will be secured a bit more. he bottom right cable coiled up is the Negative end of the pack. The positive high current cable (not shown) will connect at the upper right, then the side cover goes on! The plumbing on the other end will go much more quickly.

      The final cable is on the rear battery pack, the BMS and temperature sensor wiring are all secured. Wiring is pulled through the firewall tube of the box end cover. That side is assembled and bolted into place. On the other side, we are plumbing the modules from a 100kWh pack (6.3kWh each). They have twice the connections and odd-sized fittings as compared to the more common Tesla S modules. We have all the hose, connectors and manifold plumbing sizes figured out. But when we wired and plumbed it yesterday and connected a pump to check for leaks. We found no leaks but discovered this pump won't work with these modules. A second pump (different type) wasn't good enough either. Both of these pumps have garden-hose-like flow, but we need higher pressure. When the flow is restricted too much on these pumps the pressure drops. That's why we test before we button up.  I'll keep you posted on how we solve it.

      These images show how we are attaching the high voltage junction/fuser/contactor box (and all  other parts mounted to the rear firewall of the Beetle. All fasteners are threaded rivet-nuts or rivnuts. We drill a hole and rivet the nut into position. This way, the fasteners can be removed from this side only, without having to remove the battery pack on the other side of this wall.

      Or the right, the two 6-fuse low voltage (12V) fuse blocks and 3 cube relays for the rear of the car are mounted on the door of the high voltage box. Inside the box, the aluminum plate is cut and drilled to accept two contactors, a high voltage fuse for the rear pack, a high voltage key-switch-relay (the small black one at the top), and our Positive high current battery input cables (not routed here yet). This had to be mounted in order to cut and crimp their ends to the exact length needed. The gland nuts for the cables to pass through are also installed. When the plumbing flow is resolved, the rear pack will go into the car. We'll secure and trim its high current cables then.

      More high current cables were routed, crimped, and installed by Chris. We've had concerns with the pressure required for the P100D Tesla modules not being good enough with typical pumps. We are experimenting with a higher pressure pump. We've tried other pups, some in series, etc, trying to get the coolant flow up to par. We must find the solution that we'll install so we can check for leaks in the rear module (and front) before they go in. We can't put them into the car until this is confirmed. The delays to research and test a few options is dissapointing, but it needs to be done. I'll post images of this testing too so you can see the lines and manifolds we are dealing with.

      The throttle linkage and location were determined, a few parts were fabricated and polished (since it shows). It's about an hour from being installed and done, but it took much of a day to get the linkage and cable extension that would work. It all is looking super neat and tidy. The radiator, throttle, and possibly a pump or two have been included in the cusstom CAD design for the engine compartment floor plates. Those plates will be ordered on Monday.


      1970 VW beetle EV heater
      Unlike other beetle conversions, this will have 63kWh on board. That battery pack consumes a lot of space where other conversions have had room for luxuries like a heater. During this project, we have explored many ways to get good heat in the remaining space. That includes custom enclosures, multiple heater units, a center console to hide stuff, and add fan controls, which the original car never had. After sitting in the driver and passenger seats imagining a center console, one begins to realize the small car would feel very cramped for average-sized or bigger people. The center console remains a valid option to put around what we've done if it remains appealing. We went with a 3kW off-the-shelf heater/fan unit neatly tucked under the firewall in the center. Having open space below it feels roomy. Having the heater the cabin (vs. under the hood) will allow it to recirculate the cabin air, heating more effectively. The left and right side duct tubes will get replaced with directional and closable vents. Hot air will also be ported to the windshield defrost ports. Closing the lower vents will send all the hot air to the windshield.

      Recently it we discussed that there are no big roadblocks (anticipated) regarding parts. But as we build, a few things are requiring a bit more attention or follow-up than expected. This is par for the course and is getting worked out. While they're not big nor long delays, today's updates are dedicated to a few of those things, bulleted below.

      • The heater assembly that was recently been decided on has been back-ordered due to an unavailable 12V blower fan. I'm told it's coming, but In the meantime, we've been using one that we had on the shelf with the same outer dimensions, but a wrong pack voltage element.

      • Most coolant connectors for the Tesla P100D battery modules were included in the shipment. There are 4 needed per module. With typical Tesla Model S battery modules, these connectors are not needed nor included. But the P100D connectors are different and have no good alternative. I have been calling battery suppliers and posted on social media yesterday that we need 17 of these, plus 3 clamshell tops. I'm also reaching out to a local traveling Tesla tech to check new part availability. I've created a page to clarify the difference for these discussions and to give early warning to builders considering these modules. As of today, I found new connectors for 9,50 each, but am continuing to check around.

      •  Heat and windshield defrost ducts for Classic VW type 1 are well known for having issues. A lot of time went into exploring how to add a simple and reliable electric heat source while also being able to plumb the air to the existing vents. This week we began executing the plumbing strategy. We'll pop a hole in the top surface of the heat box (pictured a few paragraphs above). Another hole will go through the upper firewall panel above it. The 3D printed manifold pictured below will port air directly from the cabs heater box to feed 4 ports with short tubes to the windshield defroster vents. Sourcing duct hoses of the proper size and adapting at couplers where needed was the challenge. We modified the 3D print port sizes to make use of stock VW hose sizes and repositioned the ports to clear the battery box and other obstacles. Thankfully one tube was supplied with the car that we could use to verify dimensions. More hose was ordered and the latest 3D airport is being printed (lower left) as I write this update.
      VW beetle electric heat manifold
      • Engine bay floor pattern (CAD) was sent at a local laser cut shop to get us a thin pattern to verify the latest CAD geometry we have will fit, and receive the part planned to mount to it properly. This shop is usually a next-day lead time. Unfortunately, the CNC programmer had an emergency come up and has been out for two days. I spoke with him today and we should have parts Monday.

      • Correct coolant pressure and flow rate through the Tesla modules is an important part of the conversion. We've been doing some testing on the plumbed rear box of 5 modules and have learned that an upgraded pump will likely be needed. To verify the minimum requirements, we're going to fill and test the modules within the front and rear battery boxes on the bench (as a whole system) before installing them.

      This week's emphasis for Chris and I was on getting the new foam dash and related parts cleaned up, and installed. As previously discussed, the front battery box will block much of the access to dashboard switches, wiring, and fasteners. This makes restoring it a priority. 
      Don't let anyone tell you a new dash install is easy. The shaping and fitting of nearly every vent, trim piece, and switch had to be persuaded into place. It probably doesn't help that the steel of this car experienced a front-end collision and may have tweaked some geometry.
      While the car has new paint, there were unpainted areas under the windshield that would be exposed with the replacement dash. We masked and painted that flat black. Other detailed work included cleaning all knobs with a toothbrush to get 50 years of grime out of every crack.

      The metal grill's beside the speedometer and the glove box were sandblasted, but rust pitting still showed on the bare steel. After more sanding they're painted and installed. Through the slots of the metal grilles, a new coarse stainless cross-link mesh shows a nice contrast. Glove box and other fasteners were replaced with new stainless steel.

      The original heater knobs did nothing when we got it. They were crudely held in place with bolts jammed into them from behind. Originally they each opened and closed air valves. The cable control mechanism that they once connected to was missing from behind the dash, but we don't need it. We 3D printed an adapter to mate the original left knob to the half-moon shaft of a new rotary switch. The switch will enable a PTC electric heater element via a contactor, and controls the fan speeds 1, 2, or 3.

      The side vents of the new heater box pictured previously in this article may be opened or closed to change the proportion of hot air between the defrost and footwell spaces. The right knob is mounted firmly to fill the hole in the dash. Turning it won't cause it to loosen nor be harmed.
      The stereo amp, speakers, and other parts arrived soon after ordering with exception of the stereo itself that should arrive any day.

      Custom Autosound USA740 Radio in 70 VW
      The USA-740-Radio from Custom Autosound arrived. It is installed easily and has a great old-school look. It mates with the four steel tabs on the back-side of the original dash.

      Defrost ducting for 1970 electric VW beetle
      The air-port (top image) distributes the warm air to 4 original windshield-defrost vents through the original 25mm defrost tubes. The outer-most tubes each pass through another 3D printed adapter to make the shortest run to the stock dash vent ducts.

      The original windshield washer fluid on this car used air pressure from the spare tire to force fluid from a reservoir through a valve in the same switch that controls the wiper motor speed, and finally to the squirter nozzle. With most of those parts missing, we're updating to an electric windshield washer fluid pump and reservoir. The red button shown in the lower-right image will operate the pump. The original dash valve switch still rotates to operate the wiper motor.

      The lower-right image also shows a rectangular 3D printed cover that we designed to block the hole from the relocated fuse block. The wiring from the heater unit will pass through the round holes on the right side of the cover.
      Now we're routing wires from front to rear for 12V power, CAN1 and CAN2 communications, plus BMS and charger signal  wires. It's not a photogenic step in the process.

      The heater unit (with proper voltage element) has not arrived yet. Its 12V wiring to the car is done and ready to plug it in on arrival. The high voltage wiring is simply two wires to a high voltage contactor mounted on the front battery box. It will be wired and connected when the front pack goes in.

       We now have enough P100D top clamshells to assemble the front pack and will begin that next week. We can't button it up until the P100D coolant connectors arrive and are verified for proper fit and pressure testing completed. I've updated the P100D module coolant connector page with further details discovered this week. I've ordered what I believe to be the correct connectors, and have received a shipping confirmation.

      Routing of all the low-voltage power, signal, and data wires needed from front to rear went quickly.

      Electric VW Beetle floor panel

      The image above shows a draft part representing the drivers' side engine compartment floor panel resting in place. It was produced from thin aluminum to verify edge geometry and other features such as radiator mounting, etc. From this, the CAD models were updated as shown in the bottom image, and the final stainless steel parts are being laser-cut as I write this update.


      EV PTC heater box test

      Until this week, we were using a heater box that we had in stock to mock up the system. Its PTC element was the wrong voltage, but everything else was identical. The proper heater box arrived, and of course, it's not black (a must). It was scribed for the defrost porthole and cut (upper left), painted black, and bench tested with the 3D printed ductwork to confirm higher temp plastic isn't required (upper right). The 12V heater fan wiring harness was completed, secured, and tested by operating the 3-speed switch on the dash. The airflow to all six ports is excellent. The windscreen defrost airflow and temperature is impressive.


      VW Beetle front battery box, 5 Tesla P100D modules!

      Some Tesla Model S and X battery modules have wires from each of the 6 bricks inside to the connectors at the green slave boards. In a Tesla, these boards monitor and balance the module as coordinated by the main Tesla BMS. Some versions have a more fragile flex circuit (Kapton and traces) like the modules pictured that we are building with. When we began to route our Orion BMS cell tap wires, we discovered one module had a torn-off flex circuit (bottom right). Disappointing, but a part of the journey. The box needs to be disassembled to get a better look and decide the best way to make a new reliable BMS cell tap connection to the bricks in this module.

      Once the wiring of the front box is complete, we begin connecting the coolant lines for both front and rear battery boxes to run the whole coolant system on the bench. Yesterday I received tracking confirmation that the coolant connectors and hose arrived in the US and hope to see them arrive next week.

       Electric VW bug engin compartment panels by SHIFTev.com

      The stainless steel panels arrvied with a dull eggshell finish and minor scratches. Directional grain texture was added and was just aggressive enough to work through the scratches. The two large flat panels got three folds each and were ready for test fitting. Minor trimming was needed, but the parts fit into place really well. A final assembly of parts in the motor compartment is underway.

      Tesla P100D module coolant connectors  (pre-Plaid modules)

      The new connectors for the P100D Tesla modules just arrived and I have test-fit one on a P100D module. In case it's not clear, the white latches are all shown in a state that allows the two ear-hooks (what I call them) to pull inward over the aluminum collar on the Tesla Module. Pressing the white latch so its legs extend past the connector (a 5mm movement) causes the ear-hooks to expand enough to remove the connector, but not so far as to break them off. The connectors fit tighter than I expected and appear to seal and latch correctly. We will finish assembling the front pack and pressure test on the bench to confirm.

      3D printed tool for pressing nylon hose onto connector

      The press-fit of the nylon hose onto the connectors requires a special tool with a 3 week lead time. It takes a lot of force and without the tool, it is a lot like pushing a rope. Rather than wait for a tool, I looked up some clever ways people have accomplished similar press-fits like this. A homemade fuel-line tool on this z28 thread gave me an idea. A couple of hours later I was printing the parts in the image that are nested into a standard caulk gun. Solutions like this are often a gamble, but it worked amazingly. Thirty minutes later all 10 lines for the front box were pressed onto the Tesla P100D modules.

      To check clearances for the custom heater ducting and behind-the-dash access we put the front battery box into place one last time (as empty). The spare tire wouldn't fit. It's not the box in the way. It's the new wider tire on the new wider rim. The new rim will fit, but we need a narrower tire on it. I dropped it off at the tire store to return the tire and have it replaced.


      repair of Tesla S P100D module flex circuit

      A few paragraphs above I mentioned a broken cell-tap flex-circuit on one of the battery modules. These are critical for the BMS to monitor and balance the pack and a reliable fix is important. Since replacement parts are not available, some careful scraping exposed the flex circuits gold surface under the transparent Kapton coating. Then a fast touch with a fine tip solder iron is all it took to wick a nice solder bridge across each tear. Another spot nearby was beginning to tear also, so it received the same treatment. The affected area was cleaned with isopropyl and sealed with Conformal Coat. Before connecting it to the slave BMS PCB this and all other cell tap connectors were inspected and probed to be sure no other tears were present. The lower right image shows it repaired and plugged into the slave BMS PCB on the module. It is very stabilized once in place, and it is not relying on the solder bridges for mechanical strength.


      The assembly of the front box remains the priority. Here's a status update:

      Mechanical fit: It was assembled mechanically with modules, but without plumbing and wiring. That went together as planned. 

      Damage was discovered and fixed. While Chris was installing the cell tap wiring of the assembled front box, he discovered the torn cell tap circuit. The box had to be disassembled to repair it (as described above).

      Slave BMS PCB modifications & cell tap harness wiring. Since the flex circuit repair, all of the slave BMS PCBs have been modified (traces cut). This way, we can solder our cell tap wiring harness to the exposed side of the mounted BMS slave PCBs in place on the modules, without extra handling of the board, connectors, and flex circuits. The PCBs are all mounted and ready for harness wiring.

      P100D Coolant connections and routing to manifolds. Before cutting and assembling the coolant line to the new connectors, the minimum lengths from each module to its coolant manifold must be understood. This length changed because the plumbing side of the front box was designed, fabricated and powder coated before we switched from standard Tesla modules to the P100D modules. The box side-cover has slots intended for plumbing to exit, but those slots don't line up well with the P100D fitting locations. There must have been over 20 pages of sketches exploring possible routing to avoid the delay and cost of a new box side panel. The space in the box is very constrained, making hose overlaps a pinch risk. The nylon coolant line is not very flexible. With t the tightest allowable radius at about 5" or 6" they need to exit near the connections on each module. All this to say it was more difficult to accommodate the P100D coolant line routes than expected. We now have a routing plan and are proceeding to assemble!


      The front battery is nearly assembled. The cooling lines are in and had to be heated and hand formed to route them inside the box before exiting the side. This side lid was made for the standard Tesla modules that we expected to use in the beginning of this project. The slots don't line up quite right for the coolant connections found on these P100D modules. The series connection cables are all installed. The fasteners are mostly in place. Of course, a few odd sizes are needed in some places, so those will get picked up and installed next. Otherwise, what's left is to make and install the cell tap wiring harness and the thermistor (temperature sensors) harness.

      1970 VW bug EV build by SHIFTev.com
      The front battery box is mechanically assembled and external wiring has begun. The busy upper left image shows cell tap and thermistor wiring connected and shims (white) that precisely position and stabilize each of the 5 modules.

      The upper right image shows the main contactor, and the PTC heater contnactor below it. A clear protective guarding will go over this so the exposed high voltage is not accessible to curious fingers.

      The center image shows the radiators and fans mounted, with the throttle pot box in the upper left. There is more going on underneath the stainless steel panels.

      The bottom left image shows the raw fuel gauge driver PCB (blank), and the right image shows it with components soldered to it. This board has a combination of components that suit the gauge on this car.

      Not shown, the new spare tire (narrower) is on the rim and fits into the stock location under the hood.

      *** This update doesn't have images ***

      This Thanksgiving week was very short. The ten coolant lines that exit the front battery box are now plumbed to the manifolds. The coolant lines sweep down around the side and underneath the battery box to two aluminum block manifolds. One manifold is for cold coolant-in, and the other is warm coolant-out. The manifolds transition the five small tubing lines to one bigger tube. The water-out comes from the coolant connection nearest the positive-most cells, one of which has the stock Tesla temperature sensor. The BMS harness has been wired to use these sensors so that it will report what is likely to be the warmest cell temperatures.

      Next the large coolant line from the warm-out will be routed up to a fill-port at the highest point in the system alongside the battery box. Then back down near the cold-coolant manifold where both large lines will be routed parallel all the way back to pumps and radiators. This routing will go through the main center tube in the floor pan and was only recently firmed-up because we had to see exactly how the inflexible coolant lines from the battery box modules would lay.

      Two 1" holes have been drilled into the floor pan tube under the battery in front, and two more in the back of the tube to bring the lines out of the floor pan tube. Next, we'll be pulling and connecting these two main coolant lines, connecting the pumps, and radiators.

      Last updated:11/26/2021 3:44 PM PST