#REM Li-Ion Battery Management System Slave (Analogue On/Off Charger Control) By Peter Perkins. Picaxe 08M - PIC12F683 - 031108 - www.150mpg.co.uk - V1.09 Beta. **************************** General Information ********************************* The BMS modules carry no warranty or guarantee of any kind! They are used at your own risk, and I make no claims as to their suitability for a particular function. Prospective users must evaluate the system before using it, and no liability will be entertained by myself in any shape or form whatsoever. The modules and software have been produced at low cost for the benefit of the EV & electronic community. The software is available free via the internet. Users may modify or adapt the system as they see fit. If you are not fully competent to work on potentially lethal battery systems and high voltages, then do not experiment with or use this system. Be aware that vehicle modifications can lead to invalidated insurance and warranty issues. You the end user remain fully liable for any modifications made to your vehicle. ************************* Slave Picaxe 08M Pinouts ******************************* Top _____ (+ Cell Supply) +Ve -1| ^ |8- -Ve (- Cell Supply) (Program In) Rxd -2| 0 |7- Output 0 (Bypass Load Out) (Slave Bus Out/Low V Output 4 -3| 8 |6- Input 1 (RefAdc In 1.235V) (Slave Data Bus In) Input 3 -4| M |5- Output 2 (Master Bus Out/High V) ----- ************************ Slave Module Specification ****************************** Supply/Cell Voltage 1.75 - 5.00V DC (Pic limits) Average Supply Current at 4.00v <100ua Voltage Ref LM 385 1.235V accuracy 1% Supply/Cell Voltage sensing accuracy +/- 30mv Maximum balancing/bypass current with 15R resistor 333ma at 5.00V Maximum serial Bus data rate 4800 baud (Picaxe 08M limit at 8mhz) Maximum cell Capacity 65ah (65,000) (Limit of 16bit Word Master Variable) Maximum 128 Slave Modules per Master Module (Master Pic Scratchpad Ram limit) CPU Speed 31khz - 8mhz with internal resonator (Lower speed used for power saving) Permitted Working Cell Voltage Range 1.75 - 4.30V RefVADC should be 1263 but can be adjusted to compensate for variations. Note Slave Opto's are Sink driven therefore (Pic Output Low = Opto On, High = Opto Off) ***************************** Slave Clock Speeds ********************************* *********************** Reducing CPU Speed Saves Power *************************** ******** Use the slowest speed setting that gives acceptable performance ********* %00000000 = 31 kHz 19bps %00010000 = 125 kHz 75bps %00100000 = 250 kHz 150bps %00110000 = 500 kHz 300bps %01000000 = 1 MHz 600bps %01010000 = 2 MHz 1200bps %01100000 = 4 MHz 2400bps %01110000 = 8 MHz 4800bps Example = poke $8F,%01100000 'Set clock to 4 MHz ********************************************************************************** ********************** Program Size 67 out of 256 Bytes ************************** ********************************************************************************** ***************************** Simulation Notes ******************************** Use a generic adc input of 650 to simulate a cell voltage of 1.92V Use a generic adc input of 400 to simulate a cell voltage of 3.16V Use a generic adc input of 300 to simulate a cell voltage of 4.20V #ENDREM `Variables Constants and I/O definitions `Variables 16bit symbol CellV = w0 ;w0 (b0,b1) = Cell voltage (16bit value) symbol RefADC = w1 ;w1 (b2,b3) = Raw Adc input data variable range 0-1023 10bit `Constants symbol RefVADC = 63200 ;Fixed Ref Voltage Calibration LM385 1.235v * 1023 * 100 / 2 = 63200 symbol MaxVOptoOn = 365 ;Maximum Cell Voltage Opto On > 3.65V (Charger cut off Voltage) symbol MaxVOptoOff = 360 ;Maximum Cell Voltage Opto Off < 3.60V (Charger start up Voltage) symbol LoadOn = 355 ;Balancing load/bypass cut in Voltage > 3.55V symbol LoadOff = 350 ;Balancing load/bypass cut out Voltage < 3.50V symbol MinVOptoOff = 260 ;Minimum Cell Voltage Opto Off > 2.60V (Low Cell V Alarm Off) symbol MinVOptoOn = 250 ;Minimum Cell Voltage Opto On < 2.50V (Low Cell V Alarm On ) `Pins used for I/O and designations `*** Digital high/low Outputs *** symbol Load = 0 ;2W 15R Transistor driven load/bypass resistor on Output 0 symbol HighOpto = 2 ;HighOpto on Output 2 symbol LowOpto = 4 ;LowOpto on Output 4 `*** Analogue ADC Inputs *** symbol RefInput = 1 ;LM385 1.235V RefAdc on Input 1 `********************************************************************************** `********************************************************************************** Start: ;Main program start disablebod ;Disable Pic Chip Brown Out Detection to function at lower supply V poke $8F,%00010000 ;Set CPU to 125khz for minimal power consumption `********************************************************************************** Main: ;Main program loop label readadc10 RefInput, RefADC ;Measure ADC voltage reference CellV = RefVADC / RefADC * 2 ;Calculate Cell Voltage from the ADC LM385 VRef 1.235v reading if CellV > MaxVOptoOn then ;If Cell V > MaxVOptoOn then low HighOpto ;Turn on HighOpto (Warning/Charger/Controller/Regen Cutback) {Stop Charger} endif if CellV < MaxVOptoOff then ;If Cell V < MaxVOptoOff then high HighOpto ;Turn off HighOpto (Warning/Charger/Controller/Regen Cutback) {Start Charger} endif if CellV > LoadOn then ;If Cell V > LoadOn then high Load ;Turn on load (and load indicator led If fitted) endif if CellV < LoadOff then ;If Cell V < LoadOff then low Load ;Turn off load (and load indicator led if fitted) endif if CellV < MinVOptoOn then ;If Cell V < MinVOptoOn then low LowOpto ;Turn on LowOpto (Low Cell V Alarm On ) (Warning/Controller Cutback) & led if fitted) endif if CellV > MinVOptoOff then ;If Cell V > MinVOptoOff then high LowOpto ;Turn off LowOpto (Low Cell V Alarm Off) (Warning/Controller Cutback) & led if fitted) endif goto Main ;Goto program main loop