Increasing Prius Prime ZVW52 battery capacity

The ZVW52 factory battery

For the 2020 US Prius Prime, Toyota lists a lithium-ion battery rated at 351.5 V and 8.8 kWh; its brochure gives a mass of 265 lb, or about 120.2 kg. [8] A Japanese ZVW52 removal and recycling manual gives approximately 122 kg. Toyota's technical comparison of two PHEV generations lists 129 kg for both packs. These figures come from different documents and conditions. They cannot be treated as the exact mass of a particular VIN without resolving market and weighing-method differences. [1] [2]

The high-voltage pack sits at the rear, behind the rear seats and below the cargo floor. Toyota's removal procedure takes out the floor panels and storage sections, removes some rear trim and seats, disconnects the connections, and lifts the pack through the hatch. This describes the layout; it is not an instruction for working on a high-voltage system. [1]

The owner's manual shows battery air inlets by the rear seatback and warns that blocking them can limit battery charging and discharging. Toyota also issued a service bulletin for the intake filter, fan and duct on 2017–2020 Prime models. ZVW52 uses forced airflow and a separate electric heater. A cooling function before charging uses the car's air-conditioning system. This is different from the refrigerant cooling plate described by Toyota for the next Prius PHEV generation. [1] [2]

Toyota Technical Review for the 2017 PHV lists 95 cells at 25 Ah; each cell weighs 720 g and measures 148 × 26.5 × 91 mm. Panasonic separately confirms that its automotive prismatic lithium-ion batteries were used in the 2017 Prius PHV. This article applies 2017 internal details to the 2020 Prime with a qualification: the project owner reports that the 2017 and 2020 batteries share cells and construction, consistent with parts catalogues, but no teardown of the specific 2020 battery is provided. [3] [4]

Published dimensions do not fully agree: another archived Toyota/AABC document gives a height of 105 mm instead of 91 mm. The reason may relate to measurement boundaries, but that has not been confirmed. A physical fit check must measure the cells and account for terminals, insulation, compression, clearances and orientation. The summed volume of cell bounding boxes does not show whether a complete assembly fits the factory case.

Voltage and charging

The 351.5 V nominal figure belongs to the battery. Toyota describes a converter that raises voltage for the inverter to as much as 600 V. That figure applies to the converted bus; it does not set the battery's permitted maximum. The Toyota documents reviewed here do not publish the full battery-input voltage range of the power electronics. A secondary MarkLines analysis estimates about 351–399 V at the battery terminals at full charge; this is not an official Toyota limit. [11] [1]

Diagnostic values after boost, displayed PID ranges and diagnostic trouble-code thresholds also do not disclose the battery's operating limits. The project needs battery voltage and current limits, and permitted PCU operation during driving, regeneration and charging. A similar nominal voltage is not enough: the full voltage range, cell limits, protection and regenerative power must all be compatible.

Japan-market ZVW52 Prius PHV models were offered with factory CHAdeMO fast charging. Toyota stated about 20 minutes to roughly 80% under the conditions in its source. The US 2020 Prime owner's manual says DC charging cannot be used with that car. [7] The Japanese configuration shows that DC charging was integrated on the platform, but does not prove this equipment is present on a North American car or establish charging power in kilowatts. A retrofit would require checking the charging inlet, high-voltage wiring, interlocks and controls. [10] [1]

How much energy is needed?

The owner estimates a target of 77–103 km over 3–4 days, at 15–22 kWh per 100 km. Multiplying distance by consumption gives about 11.6–22.7 kWh before reserves, charging losses, cold weather, degradation and usable-charge limits. This range describes one driving profile, not a vehicle specification.

The 15–92% SOC window mentioned by the owner spans 77 percentage points. It does not prove that the battery delivers exactly 77% of nominal energy or that this is a safe window for a different chemistry. For illustration only, multiplying nominal capacity by 0.77 gives 11.55 kWh from a 15 kWh pack and 15.4 kWh from a 20 kWh pack. At 15–22 kWh/100 km, those values correspond to about 52–77 km and 70–103 km. They are not range predictions.

The upper trip case, 103 km at 22 kWh/100 km, needs about 22.7 kWh of usable energy. If the same 77% fraction were assumed, nominal capacity would need to be about 29.5 kWh. This illustrates how strongly the result depends on driving consumption; it does not prove that a pack of that size can fit or connect to the car.

Options for further assessment

Higher-capacity cells in the factory rear area

The source study examines the EVE M21-V1.2 prismatic NMC cell in the most detail. A copy of a specification hosted by a third party lists 59 Ah, 3.74 V nominal, a 2.8–4.3 V range and a mass of about 888 g. A current specification directly from EVE and the origin of any available cell batch have not been confirmed. Using those nominal figures, a 94-cell series string calculates to about 20.7 kWh, and 95 cells to about 21.0 kWh. This is arithmetic from listed ratings, not a verified vehicle configuration. [5]

At 4.3 V per cell, the upper voltage would be 404.2 V for 94s and 408.5 V for 95s. Both exceed the secondary estimate of 399 V for a fully charged factory pack. That difference alone does not establish compatibility: the battery-input limit of the PCU and the usable capacity of EVE cells when limited to a lower top voltage are unknown. Those values need confirmation before selecting the cell count.

The same EVE copy lists different currents by temperature and state of charge; these are limits in one table, not automatically a recommended charging profile. For CATL's 28 Ah LFP cell, the manufacturer's catalogue lists 26 × 148 × 95 mm dimensions and 0.73 kg mass, but it does not provide a full datasheet with voltage and current curves by temperature. Cells should be compared across charging, discharging and regeneration conditions, not by one C-rate. [6]

A calculated 95s2p arrangement using twice the factory 25 Ah cells would provide about 17.6 kWh gross but require 190 cells. The cells alone would weigh about 136.8 kg, roughly twice the mass of the factory cells. This is a reference calculation, not a recommended design; it excludes a new case, busbars, insulation, protection and thermal management.

A complete pack from another generation or model

Toyota compares the Gen4 and Gen5 PHEV packs: 8.8 and 13.6 kWh, 95 and 72 cells, and 25 and 51 Ah. Its table lists 129 kg for both packs; the Gen5 description adds a new cooling structure using the air-conditioning circuit. This shows how packaging density can improve, but it does not prove that the Gen5 battery fits or works with ZVW52. Cell series count, voltage, battery management, charging and thermal integration differ. [2]

A complete RAV4 PHEV battery also cannot be selected from capacity or label voltage alone. Dimensions, mass, cooling, voltage range and communication with the car all need to be checked. Each swap must be assessed as a system: pack, BMS, PCU, charging, interlocks and mechanical mounting.

Mass, volume and thermal layout

Subtracting the calculated mass of 95 factory cells at 720 g each from the 120–122 kg pack estimates leaves about 52–54 kg for the case, mounts, power connections, control hardware, heater and airflow path. This is a difference between figures from separate sources, not a measured mass of individual components.

Toyota gives a 145 L pack volume for the European ZVW52. This is the volume of the pack, not an empty cavity. Ducts, fan, filter, heater, busbars, clearances and service access take up space. Cell volume alone therefore cannot prove that a new assembly will fit. The case and car need to be measured, with airflow, mounts, crash protection and axle loads checked.

For the same reason, pack mass cannot be estimated by simply adding cell mass to an unchanged factory figure. New cells may require different compression, busbars, insulation, sensors, case and cooling. The initial estimate of 20–21 kWh in the factory area remains a mock-up target, not a verified package. [9]

What to establish before choosing

1. Record actual driving and wall-energy consumption on target trips; decide whether the capacity goal means gross or usable energy.
2. Measure the factory cavity and case, including airflow passages, mounts and service clearances.
3. Obtain battery-side PCU limits for the specific VIN: voltage, discharge and regenerative current, permitted charging power and temperature derating.
4. Request a current datasheet for the exact cell revision, temperature curves, traceable production and mechanical compression limits.
5. Compare candidates across the full electrical and thermal range, then assess the BMS, protection, layout and total mass.

Until those data are available, the most grounded next step is to measure the factory area and log the car while requesting a full EVE M21 datasheet and details for Toyota OEM cells. The 20–21 kWh figures for 94s/95s can guide research, but they are not a purchase specification. The upper driving-profile case cannot yet be considered covered.

Sources and limits

This article paraphrases the technical material. Catalogues and manuals cover different markets and years. Calculations are labelled as estimates; secondary or incomplete specifications are not presented as manufacturer approval. Source metadata.

1. Toyota: PHV ZVW52 battery removal and recycling manualRemoval procedure, mass and layout; Japanese-version scope.
2. Toyota Technical Review Vol.69 No.1Pages 10–11, Gen4 and Gen5 PHEV comparison.
3. Toyota Technical Review Vol.65Table 2 and the 2017 Prius PHV system.
4. Panasonic: batteries adopted for the 2017 Prius PHVSupplier release, 28 February 2017.
5. EVE M21-V1.2 specification copyThird-party copy marked confidential; currency and origin have not been confirmed with the manufacturer. For preliminary assessment only.
6. CATL overseas commercial brochure, 2022Pages 17–18; the catalogue does not contain a complete cell datasheet.
7. Toyota Prius Prime 2020 Owner's ManualCopy consulted for battery air intake, heating/cooling and charging limits.
8. Toyota Prius Prime 2020 eBrochureUS, Traction Battery section.
9. Toyota T-SB-0062-202017–2020 Prime battery intake filter/fan service.
10. Toyota: launch of redesigned Prius PHV in JapanJapan-market ZVW52 and quick charging.
11. MarkLines: Prius PHV ZVW52 onboard charger benchmarkSecondary full-charge voltage estimate; not a Toyota limit.