Customer HelpDo electric cars and hybrid cars have the same batteries?
Alec Sharma
Founder of iHybrid Battery
1. Battery Types in Electric Cars (EVs)
Electric cars are powered entirely by electricity and require large-capacity batteries to store and deliver the energy needed for propulsion.
Battery Type:
Lithium-ion (Li-ion) is the most common for EVs due to its high energy density, long lifespan, and efficiency.
Capacity:
EV batteries are much larger, typically ranging from 20 kWh to over 100 kWh, depending on the vehicle’s range requirements.
Purpose:
Provides sole energy for the vehicle’s propulsion and powers all electronic components.
Key Features:
- High energy density for extended range.
- Designed to support fast charging.
- Optimized for deep discharge cycles, as EVs fully rely on the battery.
2. Battery Types in Hybrid Cars (HEVs and PHEVs)
Hybrid cars combine an internal combustion engine (ICE) with an electric motor, using a smaller battery to assist the engine or provide limited electric-only operation.
Battery Type:
- Hybrid Electric Vehicles (HEVs): Commonly use Nickel-Metal Hydride (NiMH) or smaller Lithium-ion batteries.
- Plug-In Hybrid Electric Vehicles (PHEVs): Use larger Lithium-ion batteries compared to HEVs, but still smaller than EV batteries.
Capacity:
- HEVs: Typically between 1 kWh and 2 kWh, as they are not designed for extended electric-only range.
- PHEVs: Typically range from 8 kWh to 20 kWh to enable limited electric-only driving.
Purpose:
- HEVs: Support the ICE by providing a boost during acceleration, regenerative braking energy recovery, and stop-start functionality.
- PHEVs: Provide a combination of limited electric-only range (typically 20-50 miles) and hybrid operation with the ICE.
Key Features:
- Designed for frequent charge/discharge cycles (shallow cycles).
- Smaller and lighter than EV batteries.
Key Differences
| Feature | Electric Cars (EVs) | Hybrid Cars (HEVs/PHEVs) |
| Primary Power Source | Electric battery | Internal combustion engine (ICE) and small battery |
| Battery Type | Lithium-ion | NiMH or Lithium-ion (smaller capacity) |
| Battery Capacity | Large (20-100+ kWh) | Small (1-2 kWh for HEVs, 8-20 kWh for PHEVs) |
| Energy Usage | Solely powers the car | Assists ICE or provides short electric-only range |
| Charging | Requires external charging stations | HEVs self-charge via regenerative braking; PHEVs can plug in for charging |
Why the Difference?
• Energy Requirements:
EVs need large batteries to provide enough energy for full propulsion over longer distances, whereas hybrids use their batteries as a supplement to the ICE.
• Weight and Space Constraints:
HEVs and PHEVs prioritize smaller batteries to save weight and space, as the ICE handles most propulsion needs.
• Cost Efficiency:
Hybrid systems with smaller batteries are more affordable compared to the large batteries used in EVs.
How Safety is Implemented?
While safety is a priority for both EVs and hybrids, EVs face higher safety challenges due to their larger battery size, higher voltage, and reliance on external charging. Hybrids, with their smaller batteries and supplemental internal combustion engines, require simpler safety mechanisms. That said, both types of vehicles are designed with robust safety systems to minimize risks and ensure reliable operation.
Battery Size and Energy Density
EVs:
- EVs have large-capacity batteries (20–100+ kWh) with higher energy density to power the entire vehicle.
- The higher energy density increases the risk of thermal runaway or fire, requiring advanced cooling systems and robust protection.
Hybrids:
- Hybrid batteries are smaller (1–2 kWh for HEVs, 8–20 kWh for PHEVs) and generally operate at lower energy levels.
- Since they are less energy-dense, the risks of overheating or fire are lower, requiring less extensive cooling and safety measures.
Battery Size and Energy Density
EVs:
- EVs have large-capacity batteries (20–100+ kWh) with higher energy density to power the entire vehicle.
- The higher energy density increases the risk of thermal runaway or fire, requiring advanced cooling systems and robust protection.
Hybrids:
- Hybrid batteries are smaller (1–2 kWh for HEVs, 8–20 kWh for PHEVs) and generally operate at lower energy levels.
- Since they are less energy-dense, the risks of overheating or fire are lower, requiring less extensive cooling and safety measures.
Voltage and Electrical System Safety
EVs:
- Operate at much higher voltages (typically 400–800 volts, with some going beyond 1,000 volts in high-performance EVs).
- Higher voltages necessitate:
- Sophisticated insulation systems to prevent electric shocks.
- Emergency high-voltage disconnects for safety in collisions.
- Clear identification of high-voltage components (e.g., bright orange cables).
Hybrids:
- Typically operate at lower voltages (200–400 volts).
- Lower voltage reduces the likelihood of severe electric shocks, so hybrid vehicles may have fewer high-voltage-specific safeguards compared to EVs.
Thermal Management
EVs:
- Large batteries generate more heat during operation and charging, especially during fast charging or heavy usage.
- Advanced liquid cooling systems are used to dissipate heat efficiently and prevent thermal runaway.
- Some EVs include battery pre-conditioning systems to optimize charging and performance in extreme weather.
Hybrids:
- Smaller batteries generate less heat, and the cooling requirements are simpler. Many HEVs use air cooling instead of liquid cooling.
- Plug-in hybrids (PHEVs) may use more robust cooling systems than regular hybrids because of their larger battery size.
Crash Safety Design
EVs:
- The battery pack is often placed under the floor (in the chassis) for better weight distribution and vehicle stability. This location requires:
- Strong reinforced enclosures to protect against punctures or deformation in crashes.
- Advanced crash sensors to isolate the battery and shut down the electrical system immediately after impact.
Hybrids:
- Hybrid batteries are usually smaller and located in areas like the trunk or under the rear seats. This reduces the risk of damage during crashes but may require additional shielding.
- Hybrids rely on both the engine and battery, so even if the battery is damaged, the vehicle might still run on the engine, which has different safety implications.
Charging Safety
EVs:
- EVs rely exclusively on external charging, including fast charging stations that can generate significant heat.
- Safety measures include:
- Real-time monitoring of battery temperature and state of charge.
- Battery Management Systems (BMS) to prevent overcharging and overheating.
Hybrids:
- Regular hybrids (HEVs) do not require external charging, relying on regenerative braking and the internal combustion engine to recharge the battery, which reduces external charging risks.
- Plug-in hybrids (PHEVs) do require external charging but at lower power levels than most EVs, reducing heat generation and risks associated with fast charging.
Summary of Differences
| Aspect | EVs | Hybrids (HEVs/PHEVs) |
| Battery Size | Large (20–100+ kWh) | Small (1–20 kWh) |
| Voltage | High (400–800+ volts) | Moderate (200–400 volts) |
| Thermal Management | Advanced liquid cooling | Simple air cooling for HEVs; some PHEVs use liquid cooling |
| Crash Safety | Robust enclosures, floor-mounted | Smaller batteries, less crash exposure |
| Charging | External charging, high-power input | No charging for HEVs; lower-power input for PHEVs |
| Fire Risks | Higher due to energy density | Lower due to smaller batteries |
| Maintenance | More complex, requires specialists | Easier, especially for HEVs |
Conclusion
While both electric and hybrid cars may use Lithium-ion batteries, the size, capacity, and function of these batteries differ significantly due to the unique demands of each vehicle type. Fully electric cars rely solely on their batteries for propulsion, necessitating large, energy-dense battery packs, while hybrid cars use smaller batteries as a supplement to their internal combustion engines.