Prius Plug In P1A00, P1A61, P1A64, P1A67, P301A, P314A, P31AB

@mudder Well, I started playing around with a little research for a plug and play replacement for the "glass unit."

Seems like need two CAN lines, one for HV battery ECU plug spoofed multiframe data and one for the drivetrain Hybrid/ECO mode override since say if wanting to use a NiMH battery one will need to help preserve that battery life compared to what I and Gemini AI assume PHV Prius does to the Lithium HV pack (seem like ClaudeAI would be better guessing for coding). Mainly, not using EV mode other than first few seconds of driving up to something like 5-10mph, albeit this can be determined maybe and adjustable based on HV battery performance. I also wonder if there is an area of opportunity for better fuel efficiency performance if used in the Gen 2, since seems like the gen 2 doesn't like to use EV mode to get up to speed.

Take everything with a grain of salt, as I am no way knowing what I am doing critically thinking wise.

Basically, I'm getting feedback for chips required as (would need to look at best practices from the datasheets for implementing):

• Master Microcontroller: STM32G474RET6. This automotive-grade MCU features three independent hardware CAN-FD/CAN controllers and high processing speeds to run real-time UDS injection loops without latency.

• Analog Front-End (AFE): Analog Devices AD7280A or LTC6804-1. These integrated circuits handle up to 12V inputs per channel (perfect for the 14.4V nominal tracking curves of paired NiMH modules) and incorporate specialized internal cell balancing and diagnostic self-tests.

• Galvanic Isolation: Texas Instruments ISO7741QDWRQ1 quad-channel digital isolator to keep high-voltage spikes away from the car's 12V accessories.

• Dual CAN Transceivers: Two NXP TJA1051T/3 modules to simultaneously isolate communication blocks between the battery sensor socket and the engine computer.

To prevent the custom board from suffering the same burnout fate as the original 89892-47011 "glass unit", incorporate three critical hardware design protections:

• Over-Current Fusible Links: Place an inline 250mA fast-acting, high-voltage ceramic fuse (rated for at least 300V DC) on every single voltage sense lead before it reaches the AFE input pins. If a wiring fault shorts out, the fuse blows instantly instead of cooking the silicon layout.
• Transient Voltage Suppressor (TVS) Diodes: Connect high-voltage TVS clamping diodes (such as the SMBJ18A) between each adjacent channel tap. This clamps high-frequency electrical switching noise generated by the hybrid inverter during regenerative braking.
• Conformal Coating: Coat the fully assembled circuit board with a military-spec silicone conformal coating (e.g., MG Chemicals 422B). This safeguards your custom design from moisture condensation and dust inside the trunk's battery enclosure.

@jacktheripper Does the PHV Pip actually read 28 blocks and Dr Prius app only shows 8?

If 28, then the replacement sense battery voltage computer firmware needs to act as an automated data proxy. Translating 14 analog block inputs from a NiMH chemistry pack into a virtual 28-block lithium structure. It maps out the exact layout below:

cpp

#include <stdint.h>
#include <string.h>

#define NIMH_BLOCKS 14
#define SPOOFED_LI_BLOCKS 28
#define BATTERY_RESP_ID 0x7EB

uint16_t physical_nimh_mv[NIMH_BLOCKS]; // Populated by AFE hardware reads
uint8_t uds_tx_buffer[64]; // Full assembly buffer for ISO-TP multi-frame

// Multi-functional Translation Matrix
void Build_Spoofed_UDS_Matrix(void) {
// Step 1: Map 14 NiMH readings across 28 virtual lithium tracking blocks
for (int i = 0; i < SPOOFED_LI_BLOCKS; i++) {
int nimh_index = i / 2; // Maps two virtual frames to every one physical block

// Split the 14.4V NiMH block into two 7.2V individual virtual readings
uint16_t virtual_cell_pair_mv = physical_nimh_mv[nimh_index] / 2;

// Inject into Big-Endian UDS Array layout (offset dynamically per layout spec)
int byte_offset = 20 + (i * 2); // Structural placeholder matching factory firmware offset
uds_tx_buffer[byte_offset] = (uint8_t)(virtual_cell_pair_mv >> 8);
uds_tx_buffer[byte_offset + 1] = (uint8_t)(virtual_cell_pair_mv & 0xFF);
}

// Step 2: Enforce strict hybrid safety clamping to disable pure EV driving modes
uds_tx_buffer[10] = 0x2E; // Force State of Charge (SoC) byte to a permanent ~23%

// Inject 48°C values onto all thermistor banks to trigger cooling fans and clip power draw
uds_tx_buffer[15] = 0x58;
uds_tx_buffer[16] = 0x58;
uds_tx_buffer[17] = 0x58;
uds_tx_buffer[18] = 0x58;

// Hard clamp WOUT (Max allowed battery discharge output) to 10kW to protect NiMH cells
uint16_t restricted_wout_watts = 10000;
uds_tx_buffer[8] = (uint8_t)(restricted_wout_watts >> 8);
uds_tx_buffer[9] = (uint8_t)(restricted_wout_watts & 0xFF);
}


To complete the multi-functional feature set, configure your board's secondary CAN channel (CAN-2) to monitor the car's primary drivetrain network. Every time the car turns on, your module will actively inject driving configuration tokens over the network to enforce your preferred background mode:

cpp

// Called in the background execution loop every 100 milliseconds
void Enforce_Default_Eco_Power_Modes(bool select_power_mode) {
uint8_t mode_frame[8] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

if (select_power_mode) {
mode_frame[1] = 0x04; // Hex byte mask to force PWR MODE engagement on dash
} else {
mode_frame[1] = 0x02; // Hex byte mask to force ECO MODE engagement on dash
}

// Broadcast frame over the primary drivetrain line
CAN2_Transmit(0x520, mode_frame);
}

Kind of neat the idea of a TFT or OLED display as well with a momentary contact switch on the display unit to toggle through different metrics real time and potentially use for changing settings

Would be interesting to confirm everything using Claude AI and a OBD2 sniffer of some sort like SavvyCAN with a USB to CAN adapter plugged into the laptop. DSD Tech SH-C31A or maybe the RHO2 adapter?

 

Such a tease. Though take your time. Guessing will be popular if you can get to that $300 or something great price point I thought I heard you mention. Guessing I heard wrong, or you're anticipating high enough volume to bring down so low. Either way, I drive a gen 2 prius daily and have the gen 3 that I can. Actually, a 07 camry hybrid now registered, plated and insured to study and work on.

Awesome. Will be looking forward for a gen 2 version as well. I probably can drive a gen 2 down for you if you needed one to prototype with.

Just great to know you're still out there somewhere moving forward, thanks for the reply. Did surprise me the regenerative braking wasn't integrated from what I saw regarding the Insight. Seems like I don't understand something, maybe charge method isn't optimal I'm guessing or am I missing something BMS related?

I'm still need to read into the reasons for Passive vs Active balancing methods and the logic behind the designs, since seems like might be useful or maybe not.