« Notes and more information about EV-RATS can be found below the calculator »

Battery Electrical Information Battery cell voltage (Typ. charged OCV, Nom., Min.):       V   V   V Cells per battery: Battery capacity: Ah,   Rated at: hrs Battery Peukert's exponent: (?) Battery Internal Resistance: Ohms (?) Maximum battery discharge current: A	System Electrical Information Battery quantity in a single series string: Number of paralleled series strings:        Motor controller current limit:                  A
Physical Information Individual battery weight:        lbs. Vehicle weight (no batteries): lbs. Vehicle live load weight:          lbs. Number of wheels:	Aero & Drag Information Vehicle frontal area:                         sqft Coefficient of aerodynamic drag:      (?) Coeff of rolling resistance (per tire): (?) Coeff of resistance (Drivetrain):       (?)
Trip Information Vehicle speed:          mph Frontal wind speed: mph Road Grade: in: % degrees	Processing Options Show range and run time to: % DoD Round results to: decimal places
Results: Basic Analysis Total system voltage (Typ. charged OCV, Nom., Min.): V V V Total battery internal resistance: Ohms Theorhetical peak system power (with no voltage sag):         W    HP Corrected peak system power (accounting for voltage sag): W    HP Total system capacity to 100% DoD: Wh Total battery pack weight:   lbs. Total vehicle rolling weight: lbs. Battery weight: % of vehicle + live load weight Results: Trip-Specific Analysis Force required to overcome gravity (inclines)*:       N Force required to overcome aerodynamic drag*:    N Force required to overcome tire rolling resistance*: N Force required to overcome drivetrain resistance*: N Total force to overcome all sources of drag*:          N Power delivered*: W    HP Average energy consumption*: Wh/mile Theorhetical Battery discharge current (with no voltage sag)*:        A Total system voltage under load (accounting for voltage sag)*:       V Corrected Battery discharge current (accounting for voltage sag)*: A Run time to 80% DoD*: hrs Range to 80% DoD*:    mi Peukert's corrected total system capacity to 100% DoD*: Wh Peukert's corrected battery capacity to 100% DoD*:        Ah Peukert's corrected run time to 80% DoD*: hrs Peukert's corrected range to 80% DoD*:    mi Results: Top-Speed Analysis Maximum attainable vehicle speed: mph The maximum attainable vehicle speed is being limited by: .
EV-RATS version 1.2   |   Last modified: 01/03/2007   |   ©2006-2007 DriveEV.com and Nick Viera

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!

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©2003 - 2008 DriveEV.com and Nick Viera