BMU,Cautions,CMU, SERVICE PLUG, BALANCER,CAN, K-Line

Drawings: http://www.facebook.com/media/set/?set=a.2962156685359.2127715.1004832596&type=1&l=f57646d719

The BMU comprehensively judges and calculates the battery level (%) from the main battery conditions including the electric consumption of the main battery, the battery cell voltage or the module temperature, and also from the travel history. The calculated battery level is sent to the EV-ECU through the CAN.

Precautions
• The main battery, which is based on lithium ion cells, should be charged before all the stored energy is used up. (Don't drain the pack all the way down and the sooner it's recharged the better. The battery likes being between 40% and 80%.)
• The main battery capacity gradually decreases with the lapse of time, depending on the operating/stored conditions.
• The main battery performance varies with ambient temperature. Especially at lower temperature, the cruising range becomes SHORTER and the required time for charging becomes LONGER.
• If the vehicle is stored in extremely high or low temperature, the battery capacity may decrease rapidly.
• Even if the vehicle is not in use, the main battery may be gradually discharged and the energy stored in the main battery will be reduced.
• Storage of the vehicle for a long time with zero state on the energy level gauge would make it infeasible to charge the main battery due to the over-discharge and in some cases the main battery needs to be replaced. (The Tesla brick effect.)
• When the vehicle is parked for a long time without use, charge the main battery fully every 3 months to avoid the over-discharge.

CELL MONITORING UNIT (CMU)
The cell monitoring unit (CMU) is mounted in each module. The battery cell voltage sensor measuring the voltage of each battery cell and the module temperature sensors measuring the temperature of the module cells are mounted in the module. There are three module temperature sensors where four battery cells are connected in series and six module temperature sensors where eight battery cells are connected in series. The signal is input into the CMU. This allows the CMU to monitor each cell conditions. The CMU has the balancer that smooths voltage variations among the battery cells.

SERVICE PLUG
The service plug is placed under the driver seat <L.H. drive vehicles> or under the passenger seat <R.H. drive vehicles>. Remove the service plug before performing the check and the maintenance work on the high voltage components to ensure the job safety, shutting off the high voltage circuit. Inserting and pulling the service plug switch installed to the main battery turns ON/OFF the service plug lever.

BALANCER DRIVING CONTROL OF BATTERY CELL VOLTAGE
The voltage of the battery cell has an excessively charged range and an excessively discharged range. When the voltage of the battery cell is excessively charged, or excessively discharged, the battery cell is dramatically be deteriorated. For this reason, the BMU controls the battery cell not to be excessively charged or excessively discharged. When the main battery is charged, the BMU should control the battery cell having the highest voltage not to be in excessively charged range. When the main battery is discharged, the BMU should control the battery cell having the lowest voltage not to be in excessively discharged range. When the main battery is repeatedly charged and discharged, the voltage should vary among the battery cells. If the voltage varies, some battery cells can reach the excessively charged range or the excessively discharged range faster than other battery cells. This causes the available capacity of the main battery to decrease. For this reason, the BMU drives the balancer installed in the CMU under the specified conditions to reduce the difference in the voltage among the battery cells. This allows the available capacity of the main battery to increased.

CONTROLLER AREA NETWORK (CAN) COMMUNICATIONS
The BMU is connected with the CAN bus line to communicate with other ECU through the CAN communications. This allows the communication to be assured. For further details on the CAN, refer to GROUP 54C.

K-LINE COMMUNICATION
K-LINE communication has been adopted with EV-ECU, BMU, and MCU, as a backup for CAN communication.

Wow, this (and your transmission post) are full of great info. Some real technical details. More please, if you've got it!!

Interesting, it looks like the battery has its own CAN network for the CMUs to the BMU. Too bad there's not more detail on the cell balancing.

Here's a link to my blog posting with photos on removing the service plug.
http://www.karmanneclectric.blogspot.com/2012/02/service-my-i.html

jray3, thank you for identifying the service plug location. All my other EVs have dc motors and have a panic button (emergency disconnect), but hopefully simply turning back the ignition key on the iMiEV will work in this very very remote (I trust) eventuality. At least we don't have to wait a full second (or whatever time delay that was in the ill-fated SUV) pushing and holding some button to turn off the power.

From: http://www.analogzone.com/pwrt0207.pdf
There are two kinds of mismatch in the pack: state of charge (SOC) and capacity/energy (C/E) mismatch. SOC mismatch is more common, each problem limits the pack capacity (mA·h) to the capacity of the weakest cell.

FiddlerJohn, you've certainly got a talent for digging up the data! :ugeek:
Do you have any insight on what it would take to add the capacity for charging while driving?
I have several desires actually, one is to add a J1772 inlet to the inside of the car with a NEMA 5-20 outlet either inside the unused CHAdeMO chamber, or discretely dangling behind the rear bumper. The goal is to simplify opportunity charging and not leave valuable portable EVSE sitting on the sidewalk; keep it secured in the car...
Secondly, I've got access to a couple of range trailers, one genset and one battery, and want the ability to make use of these either while underway, or at an 'off the grid' location. Have you found the interlock circuitry that prevents charging while underway and/or do you know what steps might be taken to 'clean up' genset power as to not trip the EVSE safeties? My old Onan genset is probably not very well regulated, but the PFC20 charger feeds happily on over 3 kw from it's AC 120V output, though the SPX EVSE drops out immediately if that AC connection is made with the genset.

Here's a nice diagram of the J1772 protocol.
http://electronicdesign.com/article...Standards-For-Electric-Vehicle-Charging-64857

The Li-ion battery temperature is controlled by the cabin A/C and heating system with an AIR duct to the battery.

The big AIR duct comes from under the dash to the battery.

The water pump comes on while charging to cool the charger not for cooling the battery.

FiddlerJohn, thanks for reminding us about this posting - I had forgotten about it.
Since it's cabin air that is ducted to the battery compartment, are they assuming that what's good for the occupants is good for the battery pack and that I'm supposed to be running the a/c in summer and heater in winter? :roll:

I have stated some of this before in this forum and other places.

The BMU uses the information from the CMU or the sensor to know the main battery condition. The BMU sends the information to the EV-ECU through the CAN communication.

Input and output pin configuration of BMU connector:

1 Auxiliary battery power source
2 EV-ECU control power source
3 BMU earth
6 CAN interface (high)
7 CAN interface (low)
8 K-LINE
12 Main battery cooling fan relay
13 Main battery cooling fan PWM signal
21 Input signal for main battery cooling fan speed
31 Applied voltage for main battery current sensor
32 Main battery current sensor (high)
33 Main battery current sensor (low)
35 Main battery earth leakage sensor
37 Local CAN (for main battery) interface (high)
38 Local CAN (for main battery) interface (low)
42 Main battery current sensor earth
43 Main battery current sensor earth(shielded)
46 Main battery earth leakage sensorpre-check signal
48 CMU ID automatic number input signal
49 CMU ID automatic number output signal


MAIN BATTERY CURRENT SENSOR
The main battery current sensor is installed in the main battery. The main battery current sensor detects the amount and the direction of the current, going through the high voltage circuit, based on the flux passing through the hall element. The two sensors that have different measuring ranges are installed in the main battery current sensor. There are the main battery current sensor (high) widely measuring the current changes and the main battery current sensor (low) specifically measuring the current changes. The current value detected respectively is converted into the voltage to output it into the BMU. This allows the BMU to monitor charge and discharge conditions of the main battery.


MAIN BATTERY GROUND FAULT DETECTOR
The main battery ground fault detector is installed in the main battery. The main battery ground fault detector has the ground fault detection circuit. When a ground fault occurs in the high voltage circuit, the main battery ground fault detector should output the voltage into the BMU. This allows the BMU to detect the ground fault occurring in the high voltage circuit. The main battery ground fault detector has a pre-check circuit. When the pre-check signal is input from the BMU, the main battery ground fault detector should be quasi-state of detecting the ground fault. The BMU detects this signal to check that the main battery ground fault detector normally operates.


MAIN BATTERY COOLING FAN CONTROL
During the quick charge, large currents are input into the main battery to swiftly complete the charge. This causes the temperatures in the main battery to easily increase. For this reason, the BMU drives the main battery cooling fan, according to the main battery cooling request signal from the EV-ECU. The air circulation in the main battery cools the temperatures.

During quick charge, the BMU calculates the temperature of each battery cell, based on the information from the module temperature sensor. The BMU sends it to the EV-ECU and the compressor & heater controller through the CAN. When the highest battery cell temperature in all the battery cell temperatures exceeds the specified temperature, the EV-ECU should send the main battery cooling request signal to the BMU. The BMU receives this signal and turns ON the main battery cooling fan relay, also supplies the electric power to the main battery cooling fan. Inputting the PWM signal to the main battery cooling fan from the BMU drives the main battery cooling fan. If the temperature in the main battery exceeds the specified temperature with driving the main battery cooling fan, the BMU should send the compressor activation request signal to the compressor & heater controller through the CAN.
Immediately after a regular charge starts, the main battery cooling fan should be driven for a few seconds to prevent the clogged filter.

In the course of recording the CAN buss data during charging i discovered that the wire for terminal 12 of the BMU was not present as called out in the diagrams above--this is said to be the control line for the fan relay. Maybe the driver circuit was moved to the EV-ECU but the schematics were not changed...? If anyone else pulls the rear seat to look around you might check on that to see what you find.

Another interesting find is that the data sent from the CMU to the BMU is formatted as 48 separate CAN PIDs ranging from 0x611-614 up to 0x6C1-6C4 with 2 temperatures and 2 cell voltages each . The msb of the PID, 0x6, indicates cell data, the middle byte which ranges from 1 to C identifies the cmu module, and the lsb ranging from 1 to 4 identifies the 2-cell pair.

This is a slightly different format from the BMU data sent over the main CAN buss found in 4 PIDs, 0x6E1 to 6E4, in which an index byte ranging from 1 to 12 is sent in the data frame to identify the cmu module, and the lsb of the PID identifies the 2-cell pair.

The BMU sends a balancing-enabled command to the CMUs, and then they report back which cells actually have the balancer turned on. It would be cool to have a display of 88 LEDs that would turn on and off to indicate which cell is balancing. This may become useful some day when packs are dismantled to re-purpose for other cars and applications.

Is the cell balancing data present on the main CANbus? If so, maybe me68 or priusfan could add it to CaniOn, possibly turning those cells orange on the battery voltage bar graph. That would be really cool.

kiev said:

Another interesting find is that the data sent from the CMU to the BMU is formatted as 48 separate CAN PIDs ranging from 0x611-614 up to 0x6C1-6C4 with 2 temperatures and 2 cell voltages each . The msb of the PID, 0x6, indicates cell data, the middle byte which ranges from 1 to C identifies the cmu module, and the lsb ranging from 1 to 4 identifies the 2-cell pair.

Click to expand...

I've been sloooowly making progress on the CMU firmware. Would you have some sample data including a few CAN IDs? PM or email me if that's more convenient.

This is a slightly different format from the BMU data sent over the main CAN buss found in 4 PIDs, 0x6E1 to 6E4,

Click to expand...

Yes, I somehow assumed that they'd merely pass the data along with the same CAN ID or at least the same formatting. It drove me crazy when I started to find 6XX CAN IDs, but not 6E1-6E4.

If all goes well, I may be able to publish the CAN packets for interfacing with the CMUs directly, bypassing the BMU and all other computers. This would be ideal for using an iMiEV pack in a conversion, for example. Though your post has nearly all the details already.

It's been a couple of years so i'm a bit rusty on this. The voltage calculation is not correct formula.

i have some scans of the BMU CAN buss traffic. One is very simple with just sitting stationary and toggling the key positions to see the buss traffic when it turns on and off--a summary of this is listed below. Another is quite long (~10 Meg over 3 parts) with the EVSE plugged in, and a third scan is about 1 Meg that includes some driving.

------------------------------------------ Looks like the formatting isn't holding when posted
Summary of CMU CAN buss scan in which the ignition key was toggled ACC and ON. The buss turns off when the key is in the OFF or ACC position. i think these are the only PIDs that are used on the BMU buss.

PID 3C3 8 bytes
1 2 3 4 5 6 7 8
3C3 When key goes to ON, sends 4 messages with 0x0F in the 5th byte, then it sends ~25 messages with a temperature limit? in the 2nd byte, then sends a cell voltage in 2 bytes, and possibly a cooling or balancing? indicator in the 4th byte.

ACC=off
SCAN HEX DATA STARTS HERE WHEN KEY IS SWITCHED FROM ACC TO ON
REPEATS 4 times
0x0 0 0 0 F 0 0 0 ON
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
REPEATS 25 times
0x0 52 0 0 0 0 0 0
temp limit = 82 - 40 offset = 42C
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
REPEATS 429X
0x1 8D 0 0 0 0 0 0
cell voltage 3.98
0x1 8E 0 0 0 0 0 0 3.97
0x1 8D 0 0 0 0 0 0 3.98
0x1 8E 0 0 0 0 0 0
0x1 8E 0 2 0 0 0 0 ACC=off

repeats 4x 0x0 0 0 0 F 0 0 0 ON
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
repeats 25x 0x0 52 0 0 0 0 0 0 ON
till key off 0x0 52 0 2 0 0 0 0 ACC=off

repeats 4x 0x0 0 0 0 F 0 0 0 ON
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
0x0 0 0 0 F 0 0 0
repeats 42x 0x0 52 0 0 0 0 0 0
till end of scan0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 0 0 0 0 0
0x0 52 0 2 0 0 0 0 ON


CELL DATA FROM CMUs
PID INDEX 3 temperatures/card cell voltage cell voltage

611 0x1 0 45 45 1 8E 1 8E cmu 1
612 0x1 0 45 45 1 8E 1 8E 8-cells
613 0x1 44 45 0 1 8E 1 8E 2 cards
614 0x1 0 0 0 1 8E 1 8E

621 0x2 0 45 44 1 8E 1 8E cmu 2
622 0x2 44 44 0 1 8E 1 8E 8-cells
623 0x2 44 45 0 1 8E 1 8E
624 0x2 0 0 0 1 8E 1 8E

631 0x3 0 45 44 1 8E 1 8E cmu 3
632 0x3 44 44 0 1 8E 1 8E 8-cells
633 0x3 44 45 0 1 8E 1 8E
634 0x3 0 0 0 1 8E 1 8E

641 0x4 0 45 45 1 8E 1 8E cmu 4
642 0x4 44 44 0 1 8E 1 8E 8-cells
643 0x4 44 45 0 1 8E 1 8E
644 0x4 0 0 0 1 8E 1 8E

651 0x5 0 45 45 1 8E 1 8E cmu 5
652 0x5 45 45 0 1 8E 1 8E 8-cells
653 0x5 45 45 0 1 8E 1 8E
654 0x5 0 0 0 1 8E 1 8E

661 0x6 0 45 45 1 8E 1 8E cmu 6
662 0x6 45 FF 0 1 8E 1 8E 4-cells
663 0x6 FF FF 0 FF FF FF FF 1 card
664 0x6 0 0 0 FF FF FF FF

671 0x7 0 45 45 1 8E 1 8E cmu 7
672 0x7 45 45 0 1 8E 1 8E 8-cells
673 0x7 45 45 0 1 8E 1 8E
674 0x7 0 0 0 1 8E 1 8E

681 0x8 0 45 45 1 8E 1 8E cmu 8
682 0x8 44 44 0 1 8E 1 8E 8-cells
683 0x8 44 45 0 1 8E 1 8E
684 0x8 0 0 0 1 8E 1 8E

691 0x9 0 45 45 1 8E 1 8E cmu 9
692 0x9 44 44 0 1 8E 1 8E 8-cells
693 0x9 44 45 0 1 8E 1 8E
694 0x9 0 0 0 1 8E 1 8E

6A1 0xA 0 45 44 1 8E 1 8E cmu 10
6A2 0xA 44 44 0 1 8E 1 8E 8-cells
6A3 0xA 44 45 0 1 8E 1 8E
6A4 0xA 0 0 0 1 8E 1 8E

6B1 0xB 0 46 45 1 8E 1 8E cmu 11
6B2 0xB 45 45 0 1 8E 1 8E 8-cells
6B3 0xB 45 45 0 1 8E 1 8E
6B4 0xB 0 0 0 1 8E 1 8E

6C1 0xC 0 46 45 1 8E 1 8E cmu 12
6C2 0xC 46 FF 0 1 8E 1 8E 4-cells
6C3 0xC FF FF 0 FF FF FF FF
6C4 0xC 0 0 0 FF FF FF FF