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
Hyper9 Controllers and Motors
Operating Input Voltage Range: 62-130 volts
Rated Torque: 173 Lb Ft
Rated Power: 120 HP
Max RPM: 8,000
Weight: 120lbs
HyPer9 HV (high voltage)
Operating Input Voltage Range: 90-180 volts
Rated Torque: 172 Lb Ft
Rated Power: 120 HP
Max RPM: 8,000
Weight: 120lbs
updated 4/27/22
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. Note the small gap between the "anvil" and the right edge of the bus bar that was caused due to thermal distortion during the welding process. updated 5/6/18
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 yards $8.88)). edited 2/23/23 Updated pricing, at $11.75
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).
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. Note the small gap between the "anvil" and the right edge of the bus bar that was caused due to thermal distortion during the welding process. updated 5/6/18
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 yards $8.88)). edited 2/23/23 Updated pricing, at $11.75
updated 5/19/2023
Kapton Masking Tape for Electronics is an amber has a temperature range of -20' to 350" F and it has voltage rating of 7000 volts. The application temperature is rated at 55' to 95'F. There is an Acrylic adhesive on one side. $11.75 for 15' as of 5/19/2023.
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
DSC6101 of the copper bus bar after application of the Kapton electrical insulating tape.
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
