A 2021 Toyota Prius comes into your shop with a center multi-function display failure. Would you know where to start?
Several shop owners feel intimidated by electric and hybrid cars and aren’t confident enough to troubleshoot problems. At Amplify 2023, industry expert “G” Jerry Truglia shared his tips and strategies in the session, “Preparing for the future of hybrid and electric vehicles”.
Jerry is an instructor at the ATTS with over 30 years of experience helping shop owners and mechanics enhance their technical skills.
In this recap, we cover key electric components and safety hazards. For the complete session that goes deeper into batteries for each manufacturer, watch the full replay.
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Hybrid & electric vehicles: what’s the difference?
The key difference is that hybrid vehicles have an Internal Combustion Engine (ICE) that offers a secondary mode of propulsion for a vehicle. Compared to this, electric vehicles only have electricity for propulsion whereas hybrid vehicles can use both electricity and the ICE.
From here onwards, we’ll refer to electric vehicles and hybrid vehicles interchangeably as they contain the same electrical components that we’re about to take a look at.
Electric safety
First things first – we start the session by diving deeper into safety requirements for handling electric vehicles. Dealing with high voltage carries considerable risk and can lead to both death and serious injuries.
Once you know your way around these, you can work on these cars with confidence. Let’s explore the safety tips Jerry shared.
- Wheel chocks: Hybrid vehicle engines are shockingly silent. This means that sometimes, people don’t realize they’re on. You don’t want the vehicle moving while you’re working on it. Install a wheel chock on at least one wheel.
- PPEs: Your Personal Protective Equipment is your best friend. Do not start off any work without these. Here’s the bare minimum of what you should have for each tech at your shop:
- Individual rubber gloves
- Glove bags
- A rescue hook
Major components
Essentially, the main electric components are the battery, a generator, an inverter, a converter, and IGBTs. Here’s a look at those.
- Batteries: DC high voltage battery with nickel metal, hydrate, or lithium ion and lithium polymers.
- Motor generator: These can come with single or dual motors.
- Inverter: An inverter converts high voltage DC (direct current) to three-phase AC (alternating current) for the generator. It also boosts DC voltage to a higher AC voltage, so they can charge high voltage vehicle batteries.
- Converter: This component takes the high voltage DC and converts it into low voltage to power low voltage comps such as the 12-volt battery, sound system, light bulbs, and OBD 2 system.
- IGBTs: Defined as Insulated GA Bipolar Transistors.
Insulation tests
Each facility that handles EVs needs to carry out insulation tests and thus, needs Ohm meters. These tests help make sure all your components are functioning well.
Insulation tests check if the voltage in your wires is healthy for each comp. They can highlight shorted wires and dead circuits. You can conduct these with either meg Ohm meters for high resistance or milli Ohm meters for low resistance. Milli Ohm meters are currently just used at Toyota to test motor generators.
Batteries
Now, let’s dig deeper into EV batteries. We’ll explore the various types you’d encounter. But first, a few words of caution for batteries.
- Don’t let your batteries overheat. Roll down the windows or make sure there’s adequate temperature when you’re servicing, not too cool, not too hot.
- Recycle the batteries once you’re ready to dispose of them. There’s usually a number on the label that you can call to have the batteries picked up. They must not be thrown away as they can be toxic to the environment.
Now that that’s out of the way, most cars have different batteries in their circuits. Each manufacturer uses a different type of battery. Here are the ones you need to be familiar with.
- Cylindrical cell battery: These can be mounted anyway and are used by Honda, Ford, and now Tesla.
- Regular prismatic flat cells: These can only be mounted horizontally and are used by BMW and Volkswagen.
- Chevy Volt battery: This is a T-shaped battery and weighs about 600 pounds. It comes with the coolant and cover.
- Nissan Leaf pouch batteries: These are pouch batteries that have two cells in series and two in parallel. It’s placed under the vehicle.
- Tesla battery: These contain about 400 cells connected in both series and parallel.
All EV batteries are 360+ volts and can output over 100 amps. To reiterate, be careful as you work on these.
Fuses
Fuses in EVs play a similar role to those in traditional internal combustion engine vehicles. These are electrical safety devices designed to protect the electrical circuits in a vehicle from damage caused by excessive current flow.
In this way, these devices regulate current and offer protection from overcurrent, keeping the circuits safe.
In this example, Jerry broke down each of the numbers on the fuse.
- SOC FT2035: This is the fuse manufacturer and identifier.
- DC 500 Volts, 100 Amps: These ratings explain the regular working voltages and current the fuse can withstand.
- IR 2000: The IR stands for Initial Rush and 2000 is the current in amperes that the fuse can withstand right when the engine is switched on.
Safety interlocks
HV interlocks check if any parts of the circuit are still open on the high voltage circuit. These provide an extra safety point when you want to power down the high voltage system.
This is made possible by a relay that disconnects the system and lets you safely inspect the circuit. These System Main Relays (SMRs) connect and disconnect the high voltage circuit and can be controlled by the HV ECU or PCM.
Also, note that similar to circuit breakers, these will trip the circuit when there’s an open connection.
Motors
EV motors layout is a lot similar to an alternator. They’ve got three wire coils, a spinning bar magnet, but they’re 100% brushless motors.
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Final thoughts
EVs and hybrid vehicles are just new technology. That doesn’t mean they’re impossible to troubleshoot.
Techs need to be aware of the risks that come with these new vehicles that are coming on our roads and familiarize themselves with how they’re made.
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