# 08-15 Gen4 - BTMS coolant inspection and test

# Objective

Verify the dielectric properties, contamination level, and basic condition of the dielectric cooling fluid (light blue in colour) used in the battery packs and the BTMS of the LionC Gen4 electric bus.

The LionC Gen4 drivetrain (electric motor and related components) and the diesel heating system (if present) use the regular coolant (red in colour) found in heavy vehicles. The LionC Gen3 buses battery packs and BTMS unit don’t use coolant.

# Required Tools & Materials

Clean, dry sample container (non-conductive, preferably glass or HDPE)
Digital multimeter or conductivity meter
Syringe
Visual inspection device (a white background, a source of light)
Disposable gloves and safety glasses
Manufacturer’s specification sheet for fluid properties

# Procedure

1. Safety Preparation

Power down the vehicle and shut down the high-voltage system according to Lion high voltage safety protocol.
Wear gloves and safety glasses.
Ensure the work area is clean and free of conductive debris.

2. Fluid Sampling

Drain a small amount of cooling fluid into a suitable clean container.
Avoid contamination by using clean tools and sealing the sample immediately.

3. Visual Inspection

Check for:
- Color changes (compare to new fluid standard)
- Presence of particles or sediment
- Cloudiness or emulsification (may indicate water ingress)
If contamination is visible, fluid replacement is recommended.

4. Conductivity Meter Test

Measure the conductivity of the used fluid with a proper conductivity meter like this one:
- Make sure your meter can measure below 100 µS/cm (micro siemens per centimeter)

The maximum permissible conductivity is 100 µS/cm (micro siemens per centimeter). Any fluid recording values above should be discarded and replaced as per Lion’s repair procedure.