EV Fundamentals: Blue Lightning Lotus Evora
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Blue Lightning Lotus Evora
05.33
| 00:00 | In this section of the course, we'll be taking a high-level look at some of the real EV projects built right here at Mountain Pass Performance to help you better understand the process of designing an EV system. |
| 00:09 | First up, we'll look at my Lotus Evora Blue Lightning. |
| 00:12 | Blue Lightning was actually our first EV conversion ever and my personal introduction to EVs. |
| 00:17 | The goal with this car was to learn about EVs while also making a ton of power and achieving a range of around 150 to 200 kilometers. |
| 00:24 | It was also important that the car would be able to do at least one lap so that we could be successful in time attack with the car. |
| 00:30 | At the time, the only available OE drive unit, which is the motor and inverter combined into one unit, was from a Tesla Model S. |
| 00:37 | This set our system voltage to a target of 420 volts, because anything above that sets a fault with that drive unit. |
| 00:44 | There weren't many aftermarket controllers or any really for a Model S at the time, so we had to do some development with a company called Advantix from Switzerland to figure out how to make this motor spin and work in our application. |
| 00:54 | Once the motor was working, we designed custom mounts and welded them to the Evora's rear substructure. |
| 00:59 | Custom axles were built to interface with the Tesla CV joints on the inboard end and the Evora CV joints on the outboard end. |
| 01:05 | With the drive unit selected in the battery voltage set, the only good OE battery options, which we could use at the time were either from a Tesla Model S or a Chevrolet Volt. |
| 01:14 | The Tesla battery would have been far too heavy to produce the voltage and power we were looking for as we would have needed many modules. |
| 01:21 | The Chevrolet Volt battery has been great, offering high power cells, which make tremendous power for the capacity of the battery. |
| 01:26 | The downside is that the shape of these batteries are tough to reconfigure and being designed for the transmission tunnel of a hybrid, the capacity is quite low and they just don't fit into a lot of spaces. |
| 01:35 | Using two Chevrolet Volt batteries in parallel produced less than the ideal amount of energy, but the power potential was quite high, so that was the direction we went. |
| 01:43 | We used 2-watt cable for each battery as the current flow through the Tesla drive unit can be upwards of 1200 amps and the length of cable we were using was quite long. |
| 01:51 | With the major drivetrain components selected and the HV cable sized, the next step was testing with a single Chevrolet Volt battery connected to the Tesla drive unit on the dyno. |
| 01:59 | Once we knew how to control the drivetrain, I started on the design of all the ancillary components. |
| 02:04 | All of the control was done with MoTeC's M1 build platform using an M1 ECU. |
| 02:09 | I wrote the control software for both the battery management system and the drive unit control. |
| 02:14 | This software includes limits and safeties for the battery, as well as managing auxiliary components like DC fast charging and controls for the water pumps, fans and OEM Lotus Evora integration. |
| 02:23 | Aftermarket controllers are becoming more popular, so with careful component selection you won't need to be able to write your own control software to complete a high quality EV conversion. |
| 02:31 | You have to remember this swap was done in 2018. |
| 02:35 | A MoTeC C1212 display replaces the OEM instrument cluster creating an immersive EV experience and a CAN rotary keypad allows for selecting the drive direction, navigating menus and changing settings such as the upper charge limit through the display. |
| 02:47 | Knowing that the car wouldn't be running for longer than a lap or two at a time, cooling wasn't a critical concern. |
| 02:52 | However, I did want to recover waste heat into the cabin, so a three-way valve allows the motor loop to pipe coolant into the cabin. |
| 02:58 | I chose to run two coolant loops, one through the batteries and one through the drive unit with a common coolant reservoir, so while both coolant loops are separate, they can do some mixing. |
| 03:07 | In hindsight, having two separate reservoirs would have been a better design, as the system right now is overly complicated and doesn't bleed very easily. |
| 03:15 | The original Lotus radiator is retained along with the original coolant tubes that run through the side skirts down either side of the vehicle. |
| 03:21 | A 6.6 kilowatt charger and DC-DC combo unit was selected as this was the best balance between weight and utility. |
| 03:27 | We didn't need more charge power than this, but certainly anything less wouldn't be enough. |
| 03:32 | We developed our own J1772 control module as well, which handles all the signaling circuitry along with a wake-up system so that the vehicle powers itself on as soon as the charging cable is inserted. |
| 03:42 | The high voltage contactors selected are Gigavac GX16 contactors, which are specified to be able to carry 1200 amps of current for 100 seconds. |
| 03:50 | Note that the contactor temperature is very close to being a limiting factor here. |
| 03:54 | The same is the case with the current sensor we selected, which is a shunt type, meaning it has a resistor in it to measure current flow. |
| 04:00 | This means that it can get quite hot during operation. |
| 04:03 | Thankfully, in practice, logging the temperature of this sensor indicated that we were not near the limit and the inverter was always the first item to overheat, followed by the battery. |
| 04:11 | Contactors for the DC fast charging are much smaller, as CHAdeMO does not exceed more than around 125 amps. |
| 04:16 | With all of the components mounted, a wiring pinout and wiring diagrams were created, allowing the harness to be built properly. |
| 04:22 | A complete System 25 harness was constructed, along with spare connectors allowing for future expansion. |
| 04:28 | Although, I didn't correctly predict the future, so we've since had to make many less than optimal wiring changes. |
| 04:34 | One of the main goals of this project was to keep the weight added to the vehicle to the bare minimum, and to keep that weight central and as low in the vehicle as possible. |
| 04:41 | Considering the batteries were large and bulky, we couldn't do much to fit those low to the ground. |
| 04:45 | However, we were able to put the charger, high voltage electronics, such as the contactors, current sensor, and isolation module, all underneath the battery in an enclosed shell. |
| 04:54 | Reusing an existing aluminum box is the enclosure, which helped keep the weight down. |
| 04:58 | The main areas of improvement for the car are the power steering system and the battery. |
| 05:02 | The batteries are not fully enclosed in their own box as they should be, and in the future a custom battery design with its own enclosure would be a nice upgrade for this car. |
| 05:11 | It would also give us some additional range. |
| 05:13 | With this small battery, the large wheels, and sticky tires we have, the car doesn't go much further than 140km on a charge. |
| 05:19 | Although, in the end, the car has achieved most of its other goals. |
| 05:22 | Firstly, proving to be a very reliable and fun to drive sports car. |
| 05:25 | And secondly, winning and setting a time attack record in the Super Street class here in Canada. |
