Battery thermal management system (liquid-cooled BTMS unit)

01

Size cooling and heating capacity for the vehicle and climate

TKT's specification for its 11–12 m electric bus unit (model 10CW) lists cooling of 8–10 kW and optional heating of 6–10 kW, a coolant flow of 45–75 L/min, a weight of 40 kg and dimensions of 780 × 430 × 380 mm, for roof, side or rear mounting. The summary above the table states the cooling as 10 kW, so confirm the rating point with the supplier. TKT gives battery voltage options of DC 220–450 V, 400–750 V and 500–900 V, control power of DC 24 V/10 A or DC 12 V/20 A, CAN control and temperature control of ±0.5 ℃. [1]

TKT states that its BTMS cooling and heating capacity ranges from 3 to 10 kW to suit different commercial vehicles, for ambient temperatures up to 60 °C or down to −20 °C, and that it builds roof-, side- and chassis-mounted battery chillers. It explains the larger unit by vehicle size: a 12 m bus carries more battery packs, so more heat has to be removed or supplied. TKT also writes that the optimal battery operating temperature is 20 to 45 degrees. [1]

Editorial calculation: the coolant temperature change across the pack is heat load ÷ (mass flow × specific heat). Assuming a 50/50 ethylene glycol–water coolant with a density of about 1.07 kg/L and a specific heat of about 3.3 kJ/(kg·K) (assumed property values, not from the cited pages), 10 kW at 45 L/min gives 10 ÷ (0.75 × 1.07 × 3.3) ≈ 3.8 K, and at 75 L/min ≈ 2.3 K. Ask the supplier for the inlet–outlet difference measured on your pack. [1] [2]

Give the supplier the pack energy and chemistry, nominal and minimum–maximum voltage, peak charge and discharge power, the pack's cold-plate pressure drop and coolant volume, the hottest and coldest ambient, the mounting position and space, and the CAN messages the BMS will send.

02

Match the high-voltage window, refrigerant and protections

Hebei Nanfeng's 4.5 kW battery thermal management unit (model EHP3.0-3) lists 4.5 kW refrigeration and 5 kW heating capacity, a rated voltage of 320 V DC with overvoltage protection/recovery at 450/470 V DC and undervoltage protection/recovery at 235/250 V DC, a 20–30 V DC low-voltage supply, R1234yf refrigerant, a 34 cc compressor, 50%/50% ethylene glycol/water coolant, a working temperature of −20 ℃ to 50 ℃, IP67 protection, Φ20 mm inlet and outlet pipes, a total mass under 35 kg and CAN2.0 communication. [2]

The same page also says the units are optimised for 450–750 V DC systems, which does not match the 320 V DC rating in the table; confirm which voltage window applies to the model you are quoted. [2]

Nanfeng describes three modes chosen from the battery management system's feedback: refrigeration (compressor and fan on, coolant chilled in the battery cooler), heating (compressor off, electric heater and pump on) and self-circulation (pump only, for low thermal load). It lists protections against overload, undervoltage, overvoltage, overcurrent, overtemperature and abnormal system pressure, with parameters readable over CAN. [2] TKT names IP67 electric parts, including the electric compressor, water pump and connectors, and CAN control to prevent improper operation. [1]

03

Hold cell temperature spread, not just coolant temperature

Wen and co-authors' 2025 review of battery thermal management in electric vehicles describes liquid cooling as coolant, such as water or ethylene glycol solution, carrying heat from the pack to an external heat exchanger. They note that adding ethylene glycol lowers the freezing point and that water–glycol systems carry electrical safety concerns if they leak. [3]

The review reports a simulated air-plus-indirect-liquid design that kept maximum battery temperature below 45 °C at high temperature and high charge–discharge rates, but whose internal temperature gradient exceeded what the authors call the 5 °C safety threshold. It also reports a cold-plate channel layout that cut the maximum temperature difference by 3 K against a Z-shaped layout, and a liquid/heat-pipe hybrid holding 34.1 °C with a 1 °C differential at 2C discharge and 30 °C ambient. [3]

These are research results on specific packs, not ratings of a supplier's unit. They show why a quotation should state the cell-to-cell spread the pack maker will accept and how it will be measured, alongside the unit's coolant temperature control. [3] [1]

04

Rooftop, side, rear or chassis mounting and an optional heater

Units differ by where they mount and what they share with the vehicle's climate system. TKT lists roof-, side-, rear- and chassis-mounted units for buses, trucks and heavy equipment. [1] Nanfeng's unit has an optional heater, so the heating function is a separate line in the order. [2]

05

Compressor, chiller plate, heater and pump between the refrigerant and coolant loops

06

Cooling kilowatts, DC supply window and refrigerant decide which BTMS unit fits

07

Send the pack, vehicle and climate data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Pack: [chemistry; energy; voltage range; cell spread target]
Loads: [peak charge and discharge power; duty cycle]
Climate: [hottest and coldest ambient]
Coolant loop: [cold-plate pressure drop; volume; glycol mix]
Unit: [cooling kW; heating kW; mounting position; space]
Power: [HV window; low-voltage supply]
Control: [CAN protocol; modes; protections]

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