Electric Vehicle Frequently Asked Questions

INSTRUMENTATION

What kind of gauges do I need in my EV?

This really depends on what level of information you feel you need. Anything can be monitored if you really want to monitor it.

The instruments on an EV serve 3 basic purposes:

1) Monitor state of charge

The state of charge is generally indicated by the battery voltage at rest. An expanded scale voltmeter is the simplest instrument available to monitor this, although computerized meters called E-meters are available that actually track the amp-hours and/or kilowatt-hours used and replaced. E-meters combine the functions of voltmeters and ammeters, add other functions, and are reasonably priced.

2) Prevent damage to any components

EV's usually keep the factory tachometer or add an aftermarket one to avoid overspeeding the electric motor. Ammeters help to keep the currents within limits set by the component manufacturers.

3) Provide information that will enable the driver to enhance efficiency or performance

Tachometers help determine shift points to keep the motor in the range for best efficiency or performance. Ammeters help determine where efficiency starts to fall off. The E-meter data can be used to calculate watt-hours per mile (similar to MPG for an ICE car). Monitoring this figure can pinpoint when efficiency starts to fall, even before the driver notices a drop in performance. This can help to warn of dragging brakes, a low tire, etc. before they become a problem.

EV's have been built with instrumentation as simple as just an expanded scale voltmeter to roughly indicate the state of charge of the batteries. Other EV's have been built with separate meters for everything including battery voltage, motor current, battery current, individual battery voltages and currents, battery temperature indicators, and an E-meter. Most EV's are somewhere in between, and have a tachometer, a battery ammeter, and either an expanded scale voltmeter or an E-meter to monitor state of charge.

How do you connect and program an E-meter?

This question has not yet been answered

What is a battery monitoring system?

A battery monitoring system is a type of data aquisition system that keeps track of the status of each battery. Any number of parameters may be monitored, and they typically include temperature, voltage, and sometimes current. These systems usually have some means of interfacing with a portable computer for data logging and analysis purposes