Battery Prep

The motor was a major effort.  The next one even bigger is the battery installation.  The installation steps will be:

1.  Inventory the compoents
2.  Plan wiring the Battery Management System (BMS) 
3.  Wire the batteries for BMS
4.  Plan the location of the batteries in battery boxes
5.  Plan High Voltage (HV) wiring
6.  Wire HV 

 

Inventory the Components

5 Tesla Batteries

Five Tesla batteries in a very strong (and heavy) crated skid.  I also have one 3-battery box and one 2-battery box.  Plus some parts for the boxes.  

Then comes the added components and wires.  In the picture on the right, from top to bottom are 

   - The BMSC Controller and the BMSS Satellite
   - Four harnesses of white wires, 2 each per BMS
   - Five colored wire harnesses, 1 each for the batteries
   - Four black wire harnesses for thermisters 
   - Plug assemblies with pin inserts for the exit of the battery box

We'll see these components as we go.  The challenge can described by an assembler as to connect the batteries to the Battery Management System (BMS).  
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Plan wiring the Battery Management System (BMS) ​

The wiring above is a key but not the whole story.  My kit came with four sets of white wire harnesses as shown.  Each harness is made up of 13 wires numbered 0 (black) and 1 to 12 (white).  The position of each white wire in the harness is critical, so critical that each wire is printed with its position number 1-12.

What fooled me most was that the wires as delivered are 4 feet long.  That's the approximate size of a Tesla battery front to back.  My obvious conclusion was that the wires must in the worst case, span the entire battery.  I wondered how they connect to the battery?

Wrong.  The 4 feet allow for many installations, not mine.  For my installation the wire will be trimmed.   

On the front of each battery, EVW has attached their red "Connectivity Board".  This is wonderful since the board collects all of the connections needed in the battery and consolidates them into one plug. That plug is then used to connect a colored wire harness.  Then the challenge is to connect the white harness to the colored harness.   

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The front end of Tesla Battery with the EVWest Connectivity Board

Connectivity board harnesses

 

Wire the Batteries BMS

The objective now is to attach white wires to colored wires.  Notice that the white wires are actually number at both ends of the schematic.  At the top, wire #0 traces around to "c-" which attaches to the colored #8 - Black - C1- (module negative.  Wire #1 traces to "C1" which attaches to colored wire #10 - Brown - c1+.  Wires 2-6 attach to colored wires 7, 11, 6, 12, 5 respectively.

Trick - white wires 7 - 12 are all connected to white wire 6.

The fact that white wires 1 - 6 attach to colored wires designated to go to 10, 7, 11, 6, 12, 5 respectively works for four of the five batteries.  A close look at the picture in the planning section above that shows all five white harnesses, this schematic indicates that batteries 3 and 4 share a harness and that white wires 7 - 12 are active for battery 4 and attach to colored wires in the same sequence as 1-6 attach to battery 3.  

The recommended method for attaching these wires are to solder and shrink wrap the connections.  

​DO NOT ATTACH THE WHITE WIRE HARNESSES TO THE BMS BOX UNTIL THE WIRING IS CONFIRMED WITH THE  HARNESS TESTER.

The first picture on the right shows how the white wires are labeled.  This is wire #1 with the number upright and upside down.

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The second pictures shows the wires ready for solder with the shrink wrap waiting in place. 








​I twisted the ends together a bit to help the solder.  This picture shows the soldering done and ready for the shrink wrap.

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Done.  This was the first of the chores.  The colored wire harness shown above has 12 wires, 6 white, 1 black, and 4 thermistor wires = 11 connections.  Position 9 on the colored harness has no connection.  11 times 5 batteries means 55 solder/shrink connections.

I think I'll used shorter stripped ends going forward, about 3/8".

I wired up battery with the exception of the terminator wires.  Notice that in order to properly shrink wrap the attachment of c7-c12 onto the c6 I made a bundle.  Worked out OK.

I used the test board that came with the BMS to check wiring.  The results approximated the tag EVW put on the battery.  The values are on the right.

One might wonder why I created the chart of my test measurements.  Just a matter of documented discipline.  

Thermistor Wiring.  The note on the right tells how to identify two thermistor wires among the colored wires for attachment to the small black harness of 10 thermistor wires.  As the tables above shows, the resistance was a bit higher than expect.   I will confirmed with EVW that I should attach the Pink/Pink to the transistor plug 1 and that Purple/Purple is not used.

A check with “Temperature vs Resistance” tables indicate that the 5k to 10k ohm readings are typical at room temperature.  I wired the thermistors in my garage while it was snowing outside.  17k ohms at closer to 50 degrees confirms the thermistors are working fine.

​The thermistor plug on the LTC is a 10 pin plug.  Thermistors coming from the battery have two wires each.  Each pair is wired to an upper and lower connection pairs.

I have two LTC's each with two thermistor plugs.  I have 5 battteries.

It happens that when the ohm test shown above were completed, the pairs were consistently Pink/Pink and Purple/Purple for every battery. 

I made the chart to the right so that I could see graphically the position of every wire.  Thermistor plug 3 is shared by Battery 3 and Battery 4.

IMI/IPI - IMO/IPO  The two wire IMI/IPI to IMO/IPO is used to connect the Satellite BMS to the Master BMS.  My current thinking is that this will be a connection that runs from the 2-battery box to the 3-battery box.  It will be twisted pair, 20 gauge.  The 2-battery box has a full 6-pin plug is a hole will need t be drilled to accommodate the exit from the 2-battery box.  Connection to the satellite BMS will through the empty 6-pin plug (if I can get male/female pins) or through a drilled hole similar to the one in the 2-battery box.

BMSC to Box Plug  You will see that the white harnesses attach to the BMS boxes with matching plugs.  This is a 6-pin to 6-pin connection with push-in connections a the BMS and crimped pins for the box plug.  The 6 pins are 

      12v-
      12v+
      LP1  For alerts (see manual)
      LP2.   "     "
      CANL. 
​      CANH

I will need to make sure which is 12v+ and 12v-.  This will be needed after the battery boxes are installed and these 6 bwires are connected.  The ultimate answer was found on the BMSC itself which pictures the wiring on the left with the leftmost wire being the negative 12v.

Battery Location

The 2-battery "Beetle Box" was designed specifically for the VW Beetle.  As the only 2-battery box available from EV West, it served my purpose.  I determined that the best (only) configuration that was practical for me to use was in the trunk.  The removal of the fuel tank provided a shelf that fit the Beetle Box and the 3-battery box in floor of the trunk.  It's going to work well.  The picture here is staging.

While it was recommended that the Beetle Box be placed and then loaded, that option obviously wasn't possible.  But a close look at his picture show that if I will place a long panel on the larger battery box, supported all the way out of the trunk, I can load the box on the panel and then slide it into place. 

Of course since the battery box is to be slid into place, a clear plan had to be executed in preparing the box.  

Next we Load Battery Box

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