Loading the Battery Boxes
The challenge with our selected battery boxes is that they were engineered for a 3/2 battery split in a Volkswagen. The implication is that the engineering was for the smallest possible space for Tesla S batteries. This is good news because I don't believe that battery boxes could be built smaller. You'll see that in some of the pictures.
The contents of each of the battery boxes is similar:
- The batteries, 2 or 3 depending on the box
- A fuse for the negative lead coming from each box
- A Battery Management System controller, BMSC primary in the 2-battery box, BMSS secondary in the 3-battery box.
The primary BMSC box and secondary BMSS boxes are the same size and are wired to their batteries in the same way. The wiring of these boxes to the batteries is described in the prior page, Battery Prep, The challenge now is dealing with the 2/0 gauge wire between batteries and between batter boxes.
The contents of each of the battery boxes is similar:
- The batteries, 2 or 3 depending on the box
- A fuse for the negative lead coming from each box
- A Battery Management System controller, BMSC primary in the 2-battery box, BMSS secondary in the 3-battery box.
The primary BMSC box and secondary BMSS boxes are the same size and are wired to their batteries in the same way. The wiring of these boxes to the batteries is described in the prior page, Battery Prep, The challenge now is dealing with the 2/0 gauge wire between batteries and between batter boxes.
|
A word about the final decision to place the batteries all in the trunk. I see in some MG Experience writings that the general practice has been to load batteries split between the front and back and to custom build battery boxes.
With the selection of the Tesla S batteries, I don't have the skills necessary to fashion boxes of the quality available from EVWest. Given the batteries and boxes, I saw no way that any batteries could be under the bonnet. I suspect success in that regard used different batteries. |
|
|
Using Tesla 5 Batteries
Capacity: 232Ah, 5.3kWh Height: 3.1 Inches Width: 11.9 Inches Length: 26.2 Inches Weight: 55 Pounds Bolt Size: M8 Voltage nominal: 3.8V/Cell, 22.8V/Module Charge voltage cut-off: 4.2V/Cell, 25.2V/Module Discharging cut-off: 3.3V/Cell, 19.8/Module Maximum Discharging Current (10 sec.):750 Amps Warranty Period: One year |
|
|
The components that went into the battery loading process were:
|
|
|
|
Battery Management System made up of the BMSC (Controller) and the BMSS (Satellite). The cable is the UBS cable for computer programming of the BMS. |
|
Additional components:
|
90 degree battery bus bar - I considered very important due the confined battery boxes I chose.
The Ring Terminals were in 8mm size for the batteries and 10mm for most of the other requirements for the big cable. |
|
|
|
The 12-pin Molex plug was used in both the 2- and 3-battery boxes. The EVWest boxes were precut with the shape of this plug. The wiring is discussed below.
|
|
|
|
With exception of the Molex holes, all the rest were left to me. 2 large holes in each box for the Gland Nut for the 2/0 gauge cable in and out.
Holes were cut and countersunk for the fuse holder and cut for USB panel adapter. The BMS controllers were attached with rivets. I also show the drill bit I used to prepare the boxes and the USB panel mount connector for PC to BMS. |
|
|
|
The 3-battery box
It this box, all additional components go on one end. Here we seen the BMS controller, the main on/off switch, the negative fuse. The loose cable on the bottom left will be attached to the bottom battery + pole. The outbound - wire from the switch goes to the front of the car. The cable from the fuse leaving the box is the negative pole heading for the other battery box. The cable on the other end of the fuse will be connected to the negative pole of the of the third battery in the box. Behind this cable are the white BMSS cables that will be attached to each of the batteries. And behind those wires is the 12-pin Molex plug. Only two wires are connected to this plug, the blue tape hold the brown/yellow connect from this secondary BMS controller to the main controller in the other battery box. This outside view shows the position of the Molex plug as well as the two bolts holding the fuse, the main power switch, the six rivets holding the BMS controller and the + and - cables. The two white plugs are the evidence of mistake holes drilled for the in/out cables! Excuse the stray washers! |
|
|
One can see the crowded space in the battery box. I don't think that the 3-battery box could have been much smaller unless the support components were moved out of the box. I like them in the protection of the box. The 90 degree bus bars are visible and help manage the space. 
|
|
Three Tesla S batteries just about ready to go.
Now to the 2-battery box.
Now to the 2-battery box.
|
This drawing of the 2-battery box is not exactly as built. It shows that this box is shorter and the connections to that battery poles are tight. For in-box components, there is a narrow space running the length of the box. The fact is that this drawing and later versions (this is on white board) were really helpful in loading the box with tight wiring. |
|
|
This view shows how tight the connections to the batteries are. It is critical that everything possible be put in place before the batteries are put in the box. An implication of this view is that this box could not be much smaller. It was engineered to the extreme since it was engineered originally for a VW kit. |
|
|
This view shows the BMS Controller. It also shows the challenge of having the battery BMS connections have to be all in place waiting for the batteries. The thermistor wires can't be seen. This BMSC receives two wires sent from the BMSS in the 3-battery box. This controller outputs six wires to be routed to the front engine compartment. |
|
|
This picture shows the negative fuse mounted to the floor of the box. The cable attached to the lower pole is from the last negative pole in the 5 battery serial wiring. The upper pole is attached to a cable that loops back toward the camera and exits the box heading to the front engine area. |
|
|
In place. The 3-battery box is sitting in the Magnette truck pushed to the back. The 2-battery box is on top of it and pushed into the space where the fuel tank was.
The larger box is bolted to the floor. The smaller will be strapped in using the anchors that the fuel tank used. The Molex plug in the smaller box receives the two leads from the larger box. These leads are connected to the main BMSC box. That control box outputs six wires which are the color wires waiting for insertion into two small pipes headed for the front. Two wires are for the +/- 12 volts power; 2 signal wires; and a twisted pair for CANH and CANL. |
|
|
Delivering the power to the front with two PVC pipes. Two smaller pipes carry the BMS six wires, the CAN twisted pair in one pipe and the power and signal wires in the second.
This final photo shows the battery boxes installed in position in the Magnette trunk. |
|
|
That's all for now folks. Next step will be to position the support components under the bonnet.
Maggi EV Home ||| Motor ||| Coupling ||| Battery Prep ||| Load Battery Box ||| more to come... ..
Maggi EV Home ||| Motor ||| Coupling ||| Battery Prep ||| Load Battery Box ||| more to come... ..
