Monday, February 5, 2018

Tesla 5.3 kWh Battery Module Monitoring Board - Part 2


Previously (this blog 12/8/2016) the Tesla Battery Module Monitoring Boards were described and later an interface board (this blog 5/15/2017) that allows Tesla batteries to be connected to an Orion battery management system.

Jaroslav Alexa in the Slovak Republic ( jaroslav.alexa@gmail.com  ) made contact and he is working on a 1993 Opel Calibra .  He plans to maintain the 2.0i gas engine in the front but add an AC75 with Curtis controller that is powered with 4 Tesla batteries in the rear.  To interface the batteries he ordered 4 of the EVBimmer battery interface boards.



Picture JA214814 showing that the top of Jaroslav' board which appears to be equivalent to the boards previously examined (this blog 12/8/2016).

Jaroslav's Tesla battery board has the following markings:

PCBA, BMB, WIRE-CLP  (perhaps Printed Circuit Board Assembly, Battery Management Board)
1014183-00-0  Rev 0
2113C50004242  (perhaps 21st week of 2013)

Our Tesla battery boards have the following markings:

PCBA (1020796)
1021749-00-B Rev 03
0313KD0001147  (perhaps 3rd week of 2013)

Although the top of the Tesla battery board appears to be identical to the boards that we have worked with, and it appears that both boards were manufactured at about the same time, the circuit board bottom surface is different in that the sensor wires are directly soldered to the PC board without using any sockets.  (Pictures JA205319 and JA212739).
 
 

Picture JA205319 showing the back side of Jaroslav's board while it was being removed from the battery module.


Picture JA212739 showing what appears to be the same J1 inter battery connector (lower left with 2 green dots) but the other jumpers are all soldered directly to the PC board.
 
 
 
Picture JA215550 side view of  J4 (right) J3 (right top) and J5 (left center).   All connections were soldered to place.
 
If the white plastic connectors on the EVBimmer interface board are removed it is then  possible to directly solder the sensor wires to the board.


Picture JA212242 showing the connections after Jaroslav finished soldering the wires to the back side of the EVBimmer board.  He was able to make the new connections without removing the sockets on the front side of the board.  The wire leads from the Tesla module are not very long and a white wire was used to extend the length of the Tesla Orange wire.

Alternatively the sensor wires can be attached to the corresponding plastic connectors that would then permit direct connection to the EVBimmer board.

The surface mount connectors (male) used on the EVBimmer interface board are parts numbered S15B-PASK-2 (LF)(SN) and S04B-PASK-2 (LF)(SN).  Both can be ordered directly from JST in Japan.   As of this writing the S04B can also be obtained from DigiKey.com  .

The corresponding mating connectors (female) that would then attach to the EVBimmer board's connector include the housings (parts numbered PAP-15V-S and PAP-04V-S) and the pins (part number SPHD-002T-P0.5 ).  All of these parts are available from DigiKey.com  .  To attach the pins to the sensor wires requires a micro crimper and an Engineer PA-09 Micro Connector Crimper can be used.  The crimper is available for $38 from Amazon.com and can be found here:

https://www.amazon.com/Engineer-PA-09-Micro-Connector-Crimpers/dp/B002AVVO7K/ref=sr_1_1?ie=UTF8&qid=1517513466&sr=8-1&keywords=pa-09 





Tuesday, August 15, 2017

Tesla 5.3 kWh Battery Modules Bus Bar - Copper Prototypes

This posting is a continuation of the 6/18/17 blog posting which described a steel prototype bus bar to vertically connect multiple 5.3 kWh Tesla battery modules.

Calculations of Bus Bar dimensions.

The battery pack will initially be used with a NetGain Warp 11 motor and then later, using NetGain's new HyPer9 AC Motor.  The first motor (DC) is high performance but not easily cooled, while the AC motor can be cooled, driven with continuous operation, and it permits regenerative braking which the DC motor can not.

The specifications for both motors are as follows:


NetGain Warp 11 DC



Maximum input voltage: recommended at 170 V by some advocate 190 V

Minimum recommended input voltage:  48 V
Ideal input voltage: 144 V
200 amps for continuous operation
250 amps for 1 hour
500 amps for 5 minutes

NetGain HyPer9 AC Motor



Minimum input controller voltage: 65 V
Maximum input controller voltage: 130 V
Maximum output controller: 760 amps
Nominal input controller voltage: 100 V (120 V fully charged battery pack)
Typical fully charged battery pack voltage: 95-125 V

Normal driving amperage: 40-380 A, estimated average 200 A
Ideal amperage for continuous operation: <250 A
Normal acceleration up a steep hill: 400 A
Pedal to the floor amps: 750
Motor can provide 38 kW continuous

The battery pack under construction in this blog will be sized for 400 amps continuous current. 

Using information from the following location,

https://www.copper.org/applications/electrical/busbar/bus_table3.html 

suggests that copper measuring 1/8" x 1.00" will be good for 250-299 amps with 30' C rise under continuous use, or 350-399 amps with 50' C rise under continuous use.  Note that flat copper sheets will allow for better heat dissipation when compared to round wire.

Copper sheet 110 alloy, 0.032" x 12" x 24" was then purchased (McMaster Carr cat 8963K56, $43.96.  It is also available in bulk from Alro Steel, 0.032" x 36" x 108", at $223).
 
Laminated Copper Bus Bar Construction

It was felt that it would be more difficult to bend 0.125" thick copper sheets, so alternatively four 0.032" copper sheets were cut according to the drawing shown in picture DSC05985.  To allow for thickness of the plates and the dimensional losses expected due to bending, the terminal surfaces on each piece was slightly lengthened 0.125" .


DSC05985 of the bus bar template drawing. 



DSC05986 Multiple copies were made of the template and then they were laid out and taped to the sheet of 0.032" copper plate. 



DSC05990 Water jet cutting (a DXF or equivalent file would be required) may be preferable in the future, but for now the pieces were cut out by hand with a band saw and hack saw.

The original steel template along with a bus bar sheet were placed in a vice (DSC05994) and the copper sheets bent to desired form with a mallet..



DSC05994 showing the plastic hammer that was used to bend the copper pieces.  Initially one sheet was bent, trial fitted, and then placed back into the vice with a second copper sheet.  The second sheet was hammered down and the process repeated until all four sheets were tightly formed as is shown in picture DSC05993.



DSC05993 of the copper sheets after bending.  Initially the vertical dimension was marked on the inner face of the bottom copper sheet, and then the sheet was bent over the template corner.  Additional layers were then separately aligned with the bottom horizontal and left vertical edge of the first sheet, and then bent over the bottom sheet(s).  All of the horizontal tab lengths were intentionally made longer then required and then trimmed to final length in a single pass with a band saw.

When the four laminates were assembled together the mounting holes were drilled to accommodate the Tesla M8 bolts.

Vice grips were used to hold the left sheets together while the right side sheets were bent.

The most perplexing problem faced was how to bend two separate 90 degree bends while maintaining the required exact vertical and horizontal placement of the copper sheets.  It was elected to build a steel fixture that could be placed in a vice to hold all of the copper sheets together and allow both bends to be made before removing the copper sheets from the vice.  The fixture's dimensions were based upon the assumption that a single copper sheet was to be bent, and the upper layers would then be bent over the bottom sheet.

Construction of the Steel Bending Fixture

Two pieces of 836 steel measuring 1" x 5" x 12" and 0.625" x 5" x 12" were purchased from Alro Steel (Outlet store, 847-640-1111, $22.22 and $13.60 respectively). The thicker plate will function as the anvil and the thinner plate will serve to hold the copper in place while the bends are formed.


DSC06069 of the 836 steel plates that were used to fabricate a fixture that was then used to bend the copper sheets.



DSC06070 cutting the 1" plate.  The cut was more rapid and quieter after lubricating the blade with 10W30 motor oil.  The paper tape was placed and marked with pencil to make the endpoint more obvious.

When stacking the battery modules in the support frame, the plane of the terminals are separated by a 3.375" vertical distance.  A band saw was initially used to cut the fixture, and it was noted that the band saw blade curved slightly under load, so the step was initially cut less than 3.375".  The plate was then placed in a Bridgeport mill and the factory top edge was reduced about 0.010", and without removing the fixture from the mill, the side step was then finally cut to guarantee both parallel surfaces and the final vertical dimension of 3.375" .



DSC06073 showing the trial fitting of the previously welded steel bus bar prototype (6/18/2017 blog entry) when placed on the fixture. It was noted that apparently due to slight distortions during welding, neither of the faces of the steel template were completely flat on the "anvil" surfaces.  



DSC06075 close up view of the lower bus bar face during the prototype trial fitting.



DSC06087 showing the rounded corner of the lower bus bar face of the "anvil" that allows for the curvature of the 1/8" copper bus bar during bending.

Solid Copper Bus Bar Construction

It was difficult to cut the interior edges of the copper bus bars shown in picture DSC05986 (above) using a band saw.  Consequently, the 0.125" copper plate was initially marked using a Sharpie and a paper template.  The first cuts were then made with a Miller Spectrum 625 Xtreme plasma cutter (240 VAC, 35 amp setting), and although the copper cut rapidly, it was necessary to slow the linear movement to allow the molten copper to be blown free and not weld the parts back together on the back side.  A band saw was then used to refine the cuts followed by filing to smooth the edges.  To achieve final parallel and perpendicular outlines, the piece was mounted in the Bridgeport and all parallel lines machined (DSC06080).



DSC06080 picture of the 0.125" copper bus bar being trimmed with the Bridgeport.  The mill made it possible to make all horizontal lines parallel to each other and all of the vertical lines perpendicular to the horizontal edges.   The rounded corners were trimmed with a band saw and then sanded with a metal file.



DSC06091 showing the final solid copper bus bar prior to placing in the vice with the faceplate.  In the future, MIG welding of a 0.0625" horizontal shelf or ledge directly below the lower edge of the copper bus bar along with a 0.0625" vertical edge to the immediate left of the vertical portion of the bus bar, would provide for reproduceable placement of multiple bus bar blanks.



DSC06092 of the copper bus bar pressed between the anvil and the front plate,


DSC06096 after bending the 0.125" copper bus bar flush to the horizontal surface.  It was very easy to bend the copper and both faces of the copper bus bar fit perfectly on the battery module terminals without any changes being required.  At this point, with the ease of the use of this bending fixture, there is no longer any reason to pursue the original laminated copper bus bar design.

Bus Bar Installation

To guard against accidental contact and possible electrical shorts to adjacent areas, the bus bar was wrapped with Kapton tape (McMaster Carr 7648A734) and then covered with a fiberglass sheath (picture DSC05999 and DSC06105, McMaster part number  7324T19 ).

A temporary nylon tie off was placed at each end to help minimize the unravelling of the fiberglass cloth.



DSC06000 Kapton Polyimide tape (McMaster Carr 7648A734, 3/4" wide, 15 feet long, 0.0025" thick, 5 yds $8.88)).


DSC6101 of the copper bus bar after application of the Kapton electrical insulating tape.


 
DSC05999 of Fiberglass High temperature sleeve (McMaster 7324T19, $5.36, 3/4" ID, 60" long.)



DSC06105 of the installed final copper solid bus bar with the fiberglass sleeve.  The horizontal distance between the midlines of the M8 bolts in the  + and - terminals on the battery module is 9.0"

updated 9/2/17, 12/9/17

Thursday, August 3, 2017

Support Frame for Two Tesla 5.3 kWh Battery Modules

This build will require 6 Tesla battery modules.   After the enlargement of the wheel well (described in this blog 11/21/13) the well provides for a battery box approximately 28.5" (left to right) by 20.5" (front to back).  Although 6 Tesla batteries would fit, to better distribute the weight, 4 will be placed in the wheel well and 2 will be initially be placed in the back seat and later moved to the motor compartment.  The 2 battery box will be made taller to accommodate an Orion BMS controller and it will be 14.125" (H) x 28.125" (L) x 12.625"(W).  The 4 battery box will be 17.625" (H) x 28.125" (L) x 12.625"(W).

Battery Module Mounting

Tesla 5.3 kWh battery modules each have a 3/8" wide "fin" as part of the Aluminum extrusions that serve as the side walls of the battery module.   These fins traverse the majority of the length of the module and we were able to utilize them to support the modules within the battery box. 



DSC05299 showing one of the "side fins" that is 0.125" thick and 22.8125" long.  The 3/8" wide fin runs nearly the length of the module as is shown in pictures DSC05331 and DSC05330.



DSC05531 showing the end point of the fin at the terminal end of the battery module.



DSC05530 showing the end point of the fin at the cooling inlets of the battery module.



DSC05290 showing the outline created with a Sharpie on the 0.5" leg of one 90 degree Aluminum angle used to support the side of the module.



DSC05291 showing the landing area on the 0.5" leg of the Aluminum angle.
The loop (center) extends 0.5" from the module, while the remainder of the fin only extends outward 5/16".  On the opposite side the fin extends a uniform 3/8" for the full length, and there are no loops.  (Picture DSC05287 bottom module).



Picture DSC05287 showing the difference in the fins on opposite sides of the modules.  The bottom fin is 3/8" wide, while the upper module fin is 5/16" with a pair of loops that extend 0.5" from the body.

The first battery box prototype uses a pair of 0.25" thick 6061 Aluminum plates (Alro Steel, http://www.alro.com/ , 888-888-2576 at $70.85 each) for side walls.  To each plate (14.125" x 28.125" x 0.25") was then mounted pairs of 6061 Aluminum 90 degree angle (1/2" x 1" x 0.125").  Each pair will function to both support the battery and prevent vertical movement (Picture DSC06046).


DSC06046 showing the Aluminum angles used to support the Tesla battery modules. Each pair was cut flush with the ends of the box and were installed using 1/4" x 20 bolts (17/64" drill).  Final assembly will use nylon insert lock nuts.




Picture DSC05453 showing one of the side panels with dimensions indicated for both the structural threaded rods and the holes for the pairs of Aluminum 90 degree angles used to support the Tesla battery modules.


DSC05355 showing close up details of the hole placement dimensions on one of the two side panels.



DSC05460 showing the pairs of Aluminum angle supports (0.5" x 1.0") placed on what will be the walls of the battery box. 

The internal width of the box is maintained using three 13.5" x 0.5" stainless steel threaded rods at the top, and three 13.25" x 3/8" SS rods at the bottom of the frame.  The top threaded rods will also function as lifting points when moving the box. 


DSC05438 of the rough structure that was used for fitment testing in the BMW prior to trimming the excess length of the threaded rods (final length 14.25").  A red fiberglass insulator sheet is shown at the bottom of the box.  To prevent the threaded rods from contacting the bottom of the battery module, the final design placed the sheet above the bottom three threaded rods instead of below it as is shown in this picture.


DSC05442 showing close up of the bottom of the box prior to relocating the fiberglass above the threaded rods.


DSC05444 of the corner construction detail.  The bottom 3/8" SS threaded rod passes through the 0.125" x 1" x 0.5" Aluminum angle.  The fiberglass was later replaced with black foam and relocated above the threaded rod to prevent any contact of the bottom of the battery module with the threaded rod.



DSC05561 Showing the initial design bottom corner details and how support was provided for the bottom plate.  Note that the red GPO3 is located between the threaded rod and the bottom of the battery module to prevent accidental electrical contact.   The Aluminum end plates ( 12.5" x 14.125", picture DSC05520 at end of blog below) were attached to the support frame with Aluminum angles ( 1.25" x 1.25" x 0.125", picture DSC05518 ) and 1/4"-20 SS bolts.  The bolts were secured with steel press-fit nuts (McMaster 95185A205, 25 at $12.35, picture DSC05474).


Picture 5474 of the zinc plated steel 1/4" 20 press fit nuts.  A 11/32" drill was used to prepare the guide hole and then the nut was forced into the opening using an arbor press or large vice.



Picture DSC05518 showing the press fit nut after installation in the 0.125" Aluminum end panel bracket shown above in DSC05561.  Since the threads are located on the back side of the Aluminum angle, the end plates remain flush with the face of the box frame and tightening of the bolts pulls the press nuts into the Aluminum bracket.


DSC05524 Close up of the installed mounting brackets.  The press fit nut is adjacent to the threaded rod in the middle of the picture.  The next generation battery box should have the corner angle bracket recessed 0.125" from the left edge so that a sheet of 0.125" GPO3 can be placed between the Aluminum end plate and the bracket itself to provide additional electrical insulation for the batteries.



DSC05465 with two Tesla battery modules installed (terminal end) and prior to trimming the bottom threaded rod and attaching the corner mounting brackets. 

Leaving a space for a top fiberglass insulation sheet, an additional bracket will later be added above the top battery module to support an Aluminum plate with the Orion battery management system, a pair of fuses, a pair of Zonka relays, and terminal connections.


DSC05525 end view of the of the battery box (cooling end) prior to the installation of the press nuts at the corner angle brackets and the installation of the end plate as described in this blog on 4/12/17.

Insulating the Modules and Protecting the 18650 Battery Fuses

Each 18650 battery used in the module is connected to the steel faces of the battery pack by 
individual fuses located at both the positive and negative terminals.  The fuses blow at about 25 amps.

see:   http://electronics.stackexchange.com/questions/171797/what-are-the-technical-specifications-of-tesla-cell-level-fuses-one-fuse-per-c 

The fuses are bonded using an ultrasonic metal-metal friction welding process that combines vertical force, ultrasonic power (60 kHz) and time (100ms).   

https://chargedevs.com/features/a-closer-look-at-wire-bonding/ 

Tesla wire bonding patent: http://www.google.com/patents/US20070188147 

 During all the prototype work every effort was made to protect these fuses for fear of shorting one and damaging the module.  Careful inspection showed that the fuses are somewhat protected with individual plastic "cradles" that extend slightly beyond the surface of the battery module. 


DSC05273 showing a close up of the individual fuses that connect each battery to a common end plate.  Although the Tesla patent indicates a wire thickness of 0.38 mm, our calipers measured them to be about 0.3 mm in diameter.  The Tesla patent also indicates that each wire is "substantially Aluminum" and the wire bond to the battery is an Aluminum alloy that contains 50 ppm of Nickel and 0.5% Magnesium for additional strength. 

It is desired to place a protective fiberglass cover over each side of the Tesla modules, and I was concerned about the possible fragility of the fuse wires and wire bonds.  Close examination of the battery ends shows that each battery end resides in a clear plastic cradle which extends about 1.5 mm above the metal plate.  This plastic suggests that insulating foam and fiberglass placed against the face of the module would not be in direct contact with the individual fuses.
 


DSC05272 side view showing the plastic "cradles" that hold each battery and extend 1.5 mm beyond the face of the module.  These cradles will help prevent the fiberglass sheets from contacting and abrading the battery fuse wires.


DSC06047 Each Tesla battery module as supplied comes with a tightly fitting top and bottom protective plastic cover.

To further protect the wire fuses and the entire face of the battery module, it was decided to place individual sheets of electrical grade fiberglass between each module (DSC05281). 



DSC05281 of the 0.125" x 12" x 36" electrical grade fiberglass (also called GPO3) that was purchased to insulate each module from each other.  (McMaster Carr, part number 3345K51, at $18.48 per 12" x 36" sheet).  Foam tape was placed on the underside of the fiberglass to minimize vibration.


Picture DSC05487 bottom view of the box.  The clear plastic protective cover was maintained in the final design.  For clarity the layers were separated to show: (from the left) 0.125 bottom Aluminum sheet, black 3/4" polypropylene foam (0.5" would have been easier to install ! ),  fiberglass insulator sheet (GPO3), clear Tesla protective sheet, and finally, the battery module.


DSC05507 Picture showing all of the layers fully installed prior to adding the Aluminum bottom plate.  It was difficult to slide the Aluminum plate over both the foam and threaded rod, so the foam was cut away as shown adjacent to each threaded rod.


DSC05508 Showing the bottom after the 0.125" x 28.125" x 11.625" Aluminum bottom plate was installed.


Picture DSC05520 of one of the 0.125" x 12.625" x 14.125"end panels prior to cutting holes for the coolant lines (described in this blog 4/12/17)


Picture DSC0644  showing the final side view of the battery box.  Future improvements might include counter sinking the bolt heads or TIG welding the internal Aluminum support angles so that no support holes are required in the battery box walls.

initial posting 8/3/2017
blog updated 8/5/2017, 8/22/2017