Could someone help me figure out this HONDA BMS?

[Offroader]

This is from a Lithium titanate Honda FIT EV car. I have the 30 volt pack with attached BMS.

The BMS doesn't seem to be doing anything, I charged and discharged cells by 1 amp hour and they just stay unbalanced. All cells were balanced by .002 when I opened the pack up.

Some ideas:
Does the BMS need to be powered through the 6 pin connector or connected to the car to work? Does the BMS need to be charged or discharged at the pack level for it to work?

If anyone has any idea on what I could do to get this to balance, thanks.

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Thank you

 

[okashira]

How did you get this car. They were supposed to be destroyed./ Recycled.
I want that pack.

 

[Fishybob]

The BMS requires a seperate dc supply (I think the main micro-controller came to life when the supply hit 6 or 7 vdc but have used 12v.)
The board spits out CAN bus messages with encoded cell voltage (3 messages with binary codes for 4 cell voltages each) shortly after power-up.

I have one board with microcontroller debug connectors soldered on for both the low voltage (isolated) and high voltage sides and have identified the non-standard baud rates used on the debug serial ports.

I Have not tried taking the cells out of balance to see if balancing is enable at "power up".
I have not been able to decode much more than the cell voltage.
I have not been able to identify the main AFE/BMS chip and have set the project aside for now.

I can dig up my notes if you are still interested.

Scott.

 

[dapsyra66]

I have some of the Honda FIT LTO batteries which have been deployed in solar storage.

Can I have your notes on the BMS so that I can try my hands on making the inbuilt BMS functional.

Thank you.

 

[max22]

I'm also interested in any notes on the BMS if anyone is looking at the pack. Or just to know if anyone has been using this pack as-is, and if the cells stay balanced passively with moderate charging/discharging?

 

[Fishybob]

Hi Max22

If you have the 8 pin connector with 6 wires that was plugged into the balance board the wires are:

Red (V+) DC Supply (I have used 7-12vdc)
Black (V-)
White (CANH) CAN Bus
Yellow(CANL)
Brown(CANH) CAN Bus (same as above.)
Blue(CANL)

Using a raspberry pi with a CAN transceiver board and "can-tools" I can read repeating 8 byte messages from each board all of which contain four 12-bit cell voltages (in the first 6 bytes) and a "group" number (2 MSB of the 8th data byte.) Group b00 indicates voltages for cells 1-4, b01 indicates voltages for cells 5-8, and b10 indicates voltages for cells 9-12.

rpi> sudo ip link set can0 up type can bitrate 500000

pi@RPI0W:~/my $ candump can0 -n3
can0 20A [8] 00 00 00 00 00 00 24 06
can0 20A [8] 00 00 00 00 00 00 21 54
can0 20A [8] 53 AC FE CF EC FE 02 A3

pi@RPI0W:~/my $ candump can0 -i -n3
can0 20A [8] 00000000 00000000 00000000 00000000 00000000 00000000 00100100 00000110
can0 20A [8] 00000000 00000000 00000000 00000000 00000000 00000000 00100001 01010100
can0 20A [8] 01010101 01101100 11111110 11001111 11101100 11111110 00000010 10100101

cell 1 = b000000000000 * 1.5 mV = 0.000v
cell 12 = b110011111110 * 1.5 mV = 4.989v
(dump above is from board not attached to cells.)

I have some balance boards with duplicate "addresses" (the 0x20A above) and would trade them for addresses I don't have so that I can easily read all cell voltages from a string of battery modules on a single can bus.

If you (or anyone else) get this far (or further) let me know and I can dig up more details.

Scott.

 

[Offroader]

I'm also interested in any notes on the BMS if anyone is looking at the pack. Or just to know if anyone has been using this pack as-is, and if the cells stay balanced passively with moderate charging/discharging?

I have been using 3 and half a pack of these, or 84 cells in my hybrid car with no BMS. The cells have stayed perfectly balanced for over a year already.

You just need to check them for bad cells as some of these can have bad cells. They will go out of balance if the cell is bad.

 

[IamIan]

I have some balance boards with duplicate "addresses" (the 0x20A above) and would trade them for addresses I don't have so that I can easily read all cell voltages from a string of battery modules on a single can bus.

If you (or anyone else) get this far (or further) let me know and I can dig up more details.

FYI
A little bit of progress with
1st gen Honda Insighter's using them for PHEV conversions.

https://www.insightcentral.net/threads/honda-fit-lto-bms-discussion.125085/

Some BMS board swapping is available if you still want / need non-duplicates.

 

[Offroader]

Thanks, yeah they finally got that BMS working.

I'm kind of too lazy to do anything about this now because after using these cells in my hybrid car for 2 years now, I have yet have one single cell go out of balance. Still within .003 volts of each other.

 

[IamIan]

Thanks, yeah they finally got that BMS working.

not yet 100% .. but ..
For anyone who has one of those OEM BMS 12s boards , and wants to put it to some use.

Sense they come 'included' with the $265 for 1.1kwh LTO module .. it's not a bad deal .. battery cells and cell level voltage monitoring.
https://greentecauto.com/hybrid-battery/repurposed-batteries/20ah-lto-titanate-li-ion-scib

For the moment .. cell level battery voltage monitoring is unlocked via isolated CAN communication .. be it for 12s , 24s , 36s, 48s, 60s , 72s , etc .. one just needs each BMS to use a different ID # .. but on the above InsightCentral forum link members have extra boards they will swap with people to achieve that.

The cell to cell balancing function is not 'on' by default .. it has to be commanded to turn on for specific cell .. have not yet figured out what that specific CAN command is.

I'm kind of too lazy to do anything about this now because after using these cells in my hybrid car for 2 years now, I have yet have one single cell go out of balance. Still within .003 volts of each other.

Understandable.

I got some to put to use in a ~12kwh home solar battery .. that will (with ~20,000 cycle life) hopefully last for several decades.

 

[Fishybob]

I have some balance boards with duplicate "addresses" (the 0x20A above) and would trade them for addresses I don't have so that I can easily read all cell voltages from a string of battery modules on a single can bus.

If you (or anyone else) get this far (or further) let me know and I can dig up more details.

FYI
A little bit of progress with
1st gen Honda Insighter's using them for PHEV conversions.

https://www.insightcentral.net/threads/honda-fit-lto-bms-discussion.125085/

Some BMS board swapping is available if you still want / need non-duplicates.

Thanks for the heads up Ian. (I am going to spend a little more time with this BMS board and will post progress on insightcentral.net as that discussion looks more lively.)