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EV Components FAQ
Submitted by andrew on Sat, 02/23/2008 - 23:59
Q: What are some basic components necessary for a BEV?
A: Motor, batteries, controller, and charger.
Q: What do they do?
A: The motor converts electrical energy to kinetic energy to drive the vehicle. The batteries chemically store electrical energy for powering the motor. The controller controls the flow of electrical energy from the batteries to the motor. And, the charger delivers the energy necessary to charge the batteries in a controlled manner from an AC power source.
Q: What basic types of motors are used?
A: In most cases, low-voltage DC motors that are either permanent magnet brush/brushless, or series wound. AC induction, separately excited DC, and shunt wound DC motors are less common.
Q: Which type of motor should I use for x BEV?
A: There is no ideal motor for any particular BEV, but what's commonly used are:
● Ebike/small scooter: PM brush/burshless DC motor
● Road legal scooter: PM brush/brushless DC motor
● Motorcycle Conversion: PM brush or series wound DC motor
● Slow 4-wheel EV (NEV for example): series wound DC motor
● Car/Truck Conversion: series wound DC motor, or AC induction motor
Q: How does the motor drive the wheel?
A: There are three basic ways to drive the wheel.
1. In-wheel motor, or geared motor to drive wheel directly. These are almost always PM brush/brushless DC. They are mostly used for ebikes, small scooters, and road legal scooters.
2. Chain/belt drive of wheel directly with motor. These are common for small scooters, and motorcycle conversions.
3. Driving a differential with/without transmission. Common for 4-wheeled vehicles. Car/truck conversions usually keep the transmission.
Q: What types of batteries are used?
A: Lead-acid flooded/AGM deep-cycle, NiMH (Nickel metal hydride), NiCad (Nickel Cadmium), LiFePo4 (Lithium iron phosphate), and other lithium based chemistries such as lithium polymer.
Q: What battery technology should I use?
A: It general depends on these two factors: range, and budget. There are a lot of other factors to consider as well. Check here A Battery Guide.
Q: What type of battery is most commonly used in BEVs today?
A: AGM deep-cycle lead-acid are most commonly used, except for 4-wheeled vehicles which tend to use flooded lead-acid.
Q: Which type of lead-acid batteries should I use---AGM deep-cycle, or floodeds?
A: I recommend AGMs even though they are more expensive. I've had to experience these down sides to flooded lead acids:
● They smell
● They leak acid and corrode the battery box, in addition to leaving stains on pavement when rinsed off
● Difficult to avoid acid contact with clothing during maintenance. Acid eats clothing.
● They require adding water
● They can potentially spray acid
● They are more of a safety risk. ALWAYS WEAR SAFETY GLASSES WHEN NEAR FLOODEDS!
AGMs have none of these disadvantages. They also have numerous advantages. This answer is far from complete, but I would suggest seriously considering AGMs for any BEV.
Q: How many batteries do I need?
A: This depends on the range needed. For road scooter/motorcycle/car conversions the rule of thumb is 30% vehicle weight if using lead-acid batteries.
Q: What type of controllers are used?
A: It depends on the motor type:
PM brush/series wound DC: Pulse-width modulation with semiconductors
PM brushless: Same as for PM brush/series, but require switching 3 or more phases as well, and requires motor position input to switch the phases
AC Induction: VFD (variable frequency drive) of some type [please help me add something here]
Q: What type of semiconductors are used in controllers?
A: Mosfets for low voltage, IGBT for high voltage. If the system voltage will be over 120v, than an IGBT controller is recommended.
Q: Which type of controllers/motors could have the potential for regenerative breaking?
A: All of them, but it is more common when controlling a PM brush/brushless, or AC motor.
Q: Are there any less-expensive controllers that don't use semiconductors?
A: Yes, but none are manufactured anymore to my knowledge. Different very high-power resistors can be switched in the circuit to adjust the current flow with a very high-power type switch. Also, contactors can be used to remove/add batteries to the circuit. Check here.
Q: What type of charger do I need?
A: It is specific to the type of battery being used. Most all chargers take an AC input to charge from grid power.
Q: What are some types of lead-acid battery chargers?
A: There are transformer based, and high-frequency switching chargers. The transformer based chargers are cheaper, larger, may only have CC regulation, and are good for flooded batteries while the high-frequency switching chargers usually have both CC and CV regulation. They are more expensive, and a good choice for AGMs. Generally, the switching chargers have three stages, bulk (CC), absorption (CV), and float (lower CV).
Q: How do you recommend charging an AGM battery pack?
A: I recommend breaking the pack into 6-cell sections, and charging each section independently, or wiring all of the 6-cell sections in parallel for charging. This means you can charge two 6v batteries in series, or one 12v battery independently from the rest. Or you can wire the batteries in parallel by using high-power connectors. Here's how to do it.
Q: Is it okay to charge more than one 12v AGM in series?
A: It is not advisable unless you have some type of battery equalization, or a bypass regulator across each battery that prevents the voltage from going to high.
Q: What equalizers/regulators are available?
[this is a work in progress]
[Updated July 1, 2008. Please add any Q/A additions below and I will link them in here]