What fluid does the high voltage battery cooling system require?

The high-voltage battery cooling system in most electric vehicles and hybrids typically requires a glycol-based coolant mixed with water (using either ethylene glycol or propylene glycol). Always follow the exact specification provided by your vehicle's manufacturer in the owner’s manual.

Common coolant types used in HV battery systems

In production EVs and plug-in hybrids, the battery thermal management loop is filled with a glycol-water coolant. This is not plain water; it includes corrosion inhibitors and anti-foaming agents to protect metal components and sensors within the battery pack. The choice between ethylene glycol and propylene glycol varies by manufacturer, with some newer models favoring propylene glycol for lower toxicity concerns, while others still use ethylene glycol formulations. The key point is to use theOEM-specified fluid and mixture for your specific model.

Design variations across manufacturers

Different automakers approach battery cooling differently. Some route the battery loop as a separate circuit with its own coolant, while others share the vehicle’s primary engine cooling loop. The exact fluid type, concentration, and maintenance schedule are defined by the maker. For precise requirements, consult the vehicle’s manual or an authorized service center for your model.

Maintenance and safety considerations

These systems operate under pressure and involve electrical components, so do not attempting to service them yourself unless you are trained. Do not substitute fluids or run the system with plain water, and avoid mixing different coolant types. If you notice a leak, sweet-smelling coolant, or low coolant level indicator, stop driving and contact a qualified technician. Use only the coolant specified by the manufacturer to ensure proper heat transfer and corrosion protection within the battery loop.

Summary

Across most modern electric vehicles and hybrids, the high-voltage battery cooling system relies on a glycol-based coolant mixed with water—either ethylene glycol or propylene glycol—formulated with inhibitors as specified by the manufacturer. Always refer to the owner’s manual or a qualified service provider for the exact fluid type, mix ratio, and maintenance intervals for your model.

What kind of water do you put in a battery to recharge it?

You should put only distilled water in a car battery to maintain its electrolyte level. Tap water, bottled water, or other liquids contain minerals that can harm the battery's performance and reduce its lifespan.
 
This video shows how to check and add distilled water to a car battery: 59sMike attemptsYouTube · Dec 20, 2023
Why distilled water is essential

• Mineral-free: Distilled water is purified to remove minerals and other impurities that are present in tap water. 
• Prevents damage: These minerals can react with the battery's chemicals, disrupt the electrolyte balance, create sediment, and lead to a shorter lifespan. 
• Protects performance: Using distilled water helps maintain the battery's efficiency and ensures it can hold a charge properly. 

What to avoid

• Tap water: It contains minerals that can cause chemical imbalances and damage the battery over time. 
• Bottled water: Bottled water is not purified to the same standard as distilled water and can contain minerals. 
• Acid: Do not add more acid, as only distilled water is needed to compensate for water loss through evaporation or charging. 

Does Tesla battery coolant need to be changed?

Battery coolant: Your Battery coolant does not need to be replaced for the life of your vehicle under most circumstances. Any damage caused by opening the Battery coolant reservoir is excluded from the warranty. Brake fluid: Do not top up your brake fluid.

What is the coolant used in EV battery cooling?

Indirect Liquid Cooling
99% of the coolant is made up of a commodity such as glycol or polyglycol, and water, but the 1% additive package is what separates good from great engine protection and performance.

Which fluid is used in a cooling system?

Cooling system fluid, also known as antifreeze or coolant, is a mixture of water and a chemical like ethylene glycol that regulates an engine's temperature by absorbing and dissipating heat. It prevents the engine from freezing in cold weather and overheating in hot weather, while also lubricating components and inhibiting corrosion. There are different types, including organic acid technology (OAT), inorganic acid technology (IAT), and hybrid organic acid technology (HOAT) coolants, so it is crucial to use the correct type specified by your vehicle's manufacturer.
 
This video demonstrates how to flush and refill a car's cooling system: 59sAutoZoneYouTube · Apr 10, 2017
How it works

• A water pump circulates the coolant through the engine block to absorb heat.
• The heated coolant then flows to the radiator, where it is cooled by air passing over the radiator's fins.
• A thermostat helps maintain a consistent engine operating temperature by controlling the flow of coolant. 

Key components and types

• Base fluid: Typically a 50/50 mix of water and glycol, with water being the primary heat conductor and glycol providing freeze and boil-over protection. 
• Additives: Corrosion inhibitors and other chemicals are added to protect the system's metal components. 
• Types:
  • IAT (Inorganic Acid Technology): Uses silicates and phosphates; it is less expensive but doesn't last as long. 
  • OAT (Organic Acid Technology): Contains no silicates; it costs more but lasts significantly longer. 
  • HOAT (Hybrid Organic Acid Technology): Combines OAT and IAT technologies for a balance of protection and longevity. 

When to check or replace

• Check your vehicle's owner's manual for the recommended change interval, which can range from 30,000 to 100,000 miles or every two to five years. 
• Your engine temperature warning light illuminates. 
• You smell a sweet odor coming from the engine bay, which can indicate a leak. 
• The fluid itself looks cloudy, rusty, or discolored instead of bright and clean. 
• The engine is overheating without a clear reason. 

This video shows how to check the coolant level and identify potential issues: 1mBudget MechanicYouTube · Sep 18, 2024