Being the high voltage lead for Cal Poly Racing, I was not only responsible for the EV car battery but also the charging of the battery. The charger sits within a charger box which is seperate from the main car. Inside the charger box also sits the boards which control the charging states and monitors them. I integrated the new boards as well as suggested new QOL (quality-of-life) features.
However, the most important change I made to the charger occured because of the new battery architecture for that year. With a 20% increase in battery pack voltage & an over 20% increase in total energy (due to higher energy density batteries + extra module), the requirements for charging became more demanding. The two main challenges for charging were compatibility and charging speed.
The first main challenge was that the charger (Elcon PFC2500-288XX) would not be able to output such a high voltage if the input voltage was kept to 115VAC, basically any regular NEMA 5-15 wall outlet. However, according to the datasheet below, it can be seen that the charger can output 408V if the input voltage is 230VAC, enough for our ~400V battery.
The second main challenge of the greater energy capacity was that charging speed would drop considerably. This is important because the top-level goal is to score as many points in the June competition which is only a few days long. Therefore, it is important to have a fast charging speed to minimize downtime, thus giving the whole team more time to fix issues, tune the car setup, and complete the events.
The event organizers for the FSAE competition provide a 200+VAC input for this specific purpose, the catch however is that an SAE J1772 plug must be used in order to access this higher voltage. Almost every American EV (with the notable exception being Tesla) use a universal plug for charging.
Charging the EV Formula Car from the Cal Poly Parking Lot Charger
Bryan Lew | Electrical Engineering Student 