Battery for Emrax

Hello, I am electrical engineering student at RIT, and I am entering the FSAE EV comptetion, and I am confused about the battery calculations and capacity. Besides that we are going to use one EV motor on our car and the inventor we are using is Unitek Bamocar inverter Unitek Bamocar inverter, so I wanted to ask what is the battery capacity for an EMRAX 228 Axial flux EV motor?

Hey Moath, I don't think anyone can answer that as its the critical item that you size based on your requirements. In engineering, you typically start with laying out your targets (requirements), here you can specify your weight goals/minimum range/maximum torque requirement etc., then you model your approximate performance with various motors and gears, and lastly you pick a battery cell that gives you the correct performance and can deliver power that you need in a nice package.

Batteries are hard to do, so I would recommend laying out the battery before laying out the car, or at least do it together. Trying to manufacture a crazy shape battery or dealing with cooling after your vehicle is designed can become a massive time sink.

As Pasha said, that's not a question that can be answered, as it's going to depend on the drain current and operating voltage, and how long you will be drawing on it. Another factor may be access to re-generation, charging, and the rate/time available for between events.

I can't make a recommendation, but there are some factors to bear in mind -

The motor - https://emrax.com/e-motors/emrax-228/ and https://emrax.com/wp-content/uploads/2024/02/EMRAX_228_datasheet_v1.5.pdf -is available in 3 voltages, and so currents, and has peak and continuous power ratings those, with the event's duration and loadings, should give a good estimate of the amp-hours required - IIRC, there's an endurance one which might mean looking at a bit extra, just in case of less than full charge. OH, double check, there may be a voltage limitation for safely reasons, but generally higher voltage may be preferable for higher efficiency and the ability to use lighter wiring, as the current will be lower - but that's a trade-off between weight and copper losses!

The controller/inverter you're actually using for the motor - this will be chosen to match/meet the motor voltage and current peaks for the output, but there may be options for the input voltage/amperage with differing efficiencies. While there may be a voltage limit, usually the higher the better, like for the motor.

When you know the inverter input voltage and current, then you can look at the battery configuration to give the required voltage and current, while having the total amp-hour capacity needed, AT A MINIMUM! Some battery configurations may need more careful cooling, and have different charging times, than others.