« Notes and more information about EV-RATS can be found below the calculator »
EV-RATS Notes and Disclaimer:
1] Results labeled with "theoretical" are just that -- theoretical values that will basically never be attainable in real-life. These values are shown only for the entertainment value of seeing how good things would be in an ideal world verses real-life.
2] Currently this script calculates forces, power consumption, efficiency, range, run time, and discharge currents associated with running the vehicle at a *constant* speed (the one you input), and until the batteries are discharged to the DoD you select. These results are marked with an asterisk.
3] There will be some discrepancy in Real-life range and run-time versus what the script calculates. This is because the script currently assumes the vehicle is always being powered, yet real-life driving also consists of times when the vehicle is coasting. During these times the vehicle will use almost no power from the battery pack, and the pack may have a chance to recover between (usually heavy) discharges. Both these factors may increase or decrease the actual available range and run time, condition dependent.
4] The script calculates the vehicle's attainable top-speed by obtaining the peak power capability of the battery pack and determining to what vehicle speed the batteries will still have just enough power to overcome aerodynamic drag and gravity. Thus top speed will be directly affected by the user inputs: Maximum battery discharge current, Minimum allowable battery cell voltage, and Road grade.
5] Peukert's corrected range and run time should be duly noted, especially when using Lead-Acid batteries! Notice that Peukert's effect will tend to reduce available range and run time *significantly* (compared to the non-Peukert's corrected range and run time values). Sorry, that's real-life.
6] Do some searching online for reasonable values for the coefficients of drag and rolling resistance. For example, Wikipedia has a list of Coefficients of Drag (Cd) for some vehicles: http://en.wikipedia.org/wiki/Coefficient_of_drag. This site also has lots of vehicle Cd and frontal area figures: http://www.mayfco.com/tbls.htm
7] The "Total system voltage under load" result uses the battery pack's typical charged OCV as the base voltage before calculating the voltage to which the pack will sag while loaded with the calculated current. This provides a much more accurate result than using the pack's nominal OCV in the calculations.
Final Disclaimer: This EV-RATS calculator script was written with an attempt at being as accurate as possible at determining an EV's range, top speed, and acceleration capabilities. However, it is just that; an attempt, and only an attempt. Its real-life accuracy is not known or guaranteed, and will vary based on the accuracy of the inputted variables. If you go out to the garage and blindly build or modify your EV expecting to obtain the range, performance, and/or top speed predicted by this script, well... we will be flattered. But don't bother sending angry E-mails when things don't work out exactly as planned because, well, we've now typed 107 words telling you why they probably won't. This script, DriveEV.com, and we are not responsible for mistakes!