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Home > News of Winston Battery/LiFePO4>E-bike BMS

Product Overview

We are upgrading the BMS,new version available now :-)

BMSBattery management system

                          
               
     battery bms             


EVLithium BMS

Programmable EVLithium EBS-BMS Functions & Settings

Introduction


The programmable E-Bike Smart BMS (EBS-BMS) applies to superpower E-bike or E-motor which are equipped with a li-ion battery packs using less than 24 cells in series. (≤24s and any number of parallel cells).  

The EBSBMS uses Linear Technologies battery management chip LTC6803,and microprocessor to achieve high accuracy, stability and safety.







Features


· supports 4-24s Li-ion battery pack,max 100V

· controls max.30A charging current, no limit discharging current 

· controls E-bike electric lock (e-lock for short below), control E-bike throttle

· balances passively max 23 cells simultaneously at max. 200mA bleeding current

· monitors max. 4 external temperatures and 1 internal temperature

· monitors charging current with built-in sensor (+-50A) and discharging current with external sensor (+-200A/400A) 

· supports 2.8inch LCD display

· includes professional PC software for parameter setting via TTL-USB adaptor cable






  The BMS does:

· monitor all cell voltages V_cell

· monitor the battery pack current I_bat

· monitor battery pack and BMS temperature T_pack(4 channels) and T_sys  (1 channel)

· SOC automatically learning and calculation 

depending on the parameter settings the BMS will:


· detect and handle alarming situations (OV, UV, OC, UT, OT) by disconnecting e-lock/throttle or charger

· detect and handle charge and discharge limits of the battery pack

· detect unbalanced cells and control bleeding


EVLithium EBS-BMS

(Smart BMS for E-bike Throttle Control)

battery pack configuration

4-24s

DCHG current handling capacity

nominal: no limit (Choose appropriate CS) 

CHG current handling capacity

max continuous: 30A

supply voltage

10V-100V for 4-24S

passive cell balancing

200mA,,max 23 cells simultaneously 

SOC (calculated)

accuracy ±2.5% over one cycle

V_cell measurement

resolution 5mV, accuracy ±0.2%

current measurement

Internal CS for charging ±50A ±2.0%

external CS for discharging, ±100 - 600A ±2.0%

supply current

20mA normal(e-lock is on)

0mA standby(e-lock is off) 

communication 

TTL-USB for PC and LCD

throttle control

PWM 5kHz, for clamping Hall element throttle 

signals 1-4V

auxiliary control

Cool and heat control signal (opto coupled open 

collector)



About supply current
· when customers turn off e-lock,BMS will also be turned off  and no power consumption any more
· when customers forget to turn off e-lock(e-bike is no discharging and charging),BMS will be alarm
  when UV
(will not be turn off e-lock and throttle at this situation).BMS will turn off e-lock and throttle
  until the battery pack is deeply lack of electricity
· When charger on, BMS will open to normal state and check the voltage of cells,if cells are under
   CHG_Recover,

the e-lock will be automatically on and begin charging.(not all the chargers.)


Processing Logic

States (For charging)

CHG FET

V_cell>= CHG_Limit

OFF

V_cell<=CHG_Recover

ON

Over T_pack

OFF

Over T_pack Recover

ON

Over T_sys

Keep original state

Under T_pack

OFF

Under T_pack Recover

ON

Over Charging I_bat

OFF and Recover after 3 min

Plug on charger  

when e-lock is off

V_cell>= CHG_Recover             OFF

V_cell<= CHG_Recover                 On,e-lock on


sp;�ns���;�ging, ±100 - 600A ±2.0%

supply current

20mA norma (e-lock is on)

0mA standby (e-lock is off)  

communication
TTL-USD for PC and LCD

throttle control

PWM 5kHz, for clamping Hall element throttle signals 1-4V

auxiliary control

Cool and heat control signal (opto coupled open collector)

States (For discharging)

 E-lock and Throttle

V_cell<= DCHG_Limit

 OFF

V_cell>=DCHG_Recover

ON

Over T_pack

OFF

Over T_pack Recover

ON

Over T_sys

Keep original state

Under T_pack

OFF

Under T_pack Recover

ON

Over Discharging I_bat

OFF and Recover after 5 min


Opto-coupler switch

Opto-coupler switch is in P8.

Discharging on, DCHG opto LED ON. 
Current will be permitted between DCHG-A&DCHG-B. 

Charging on.CHG opto LED ON.
Current will be permitted between CHG-A&CHG-B.



PWM




PWM State

When battery is in lower power state,signal of throttle controller will be changed by BMS.


When battery is in normal state,voltage of throttle in and throttle out are the same.

When battery is in lower power state,output signal will be 50% duty ratio modulated by

PWM signal in order to let output power reduce to 50%.Recuperation Current


BMS has two current sensor.One is the internal CS(current sensor) to monitor charging current.


The other is the external CS to monitor discharging current.Besides that,external CS can also 

monitor recuperation current.This kind of CS is the two-way current sensor.When e-bike is downhill 

or braking,recuperation current will be monitored and BMS will calculate this part of current to SOC.

(In general,customers use 100BT or 200BT external SC,so if recuperation current is too small,CS 

can not monitor and BMS will not be calculate it to SOC.)




8. BAT-,     2. CHG-,     3. LCD, 4.Temperature sensor (4 channels),        5. External Temperature sensor

9. Cell 13-24 monitoring/bleeding (No.2 JST  18pin),     7. Cell 1-12 monitoring/bleeding (No.JST  16pin)

10. Buzzer,     9. TTL-USB,     10 Throttle/E-lock connector    11. firmware update



P5

P5-1

B-

P5-2

B-

P5-3

B1+

P5-4

B2+

P5-5

B3+

P5-6

B4+

P5-7

B5+

P5-8

B6+

P5-9

B7+

P5-10

B8+

P5-11

B9+

P5-12

B10+

P5-13

B11+

P5-14

B12+

P5-15

B12+

P5-16

NC

P6 

P6-1

B13-

P6-2

B13-

P6-3

B13+

P6-4

B14+

P6-5

B15+

P6-6

B16+

P6-7

B17+

P6-8

B18+

P6-9

B19+

P6-10

B20+

P6-11

B21+

P6-12

B22+

P6-13

B23+

P6-14

B+

P6-15

B+

P6-16

NC

P6-17

NC

P6-18

NC

P7

P7-1

+5V

P7-2

HALL

P7-3

GND

P7-4

NC

P1 

P1-1

NTC1+

P1-2

NTC1-

P1-3

NTC2+

P1-4

NTC2-

P1-5

NTC3+

P1-6

NTC3-

P1-7

NTC4+

P1-8

NTC4-

P2 

P2-1

+5V

P2-2

GND

P2-3

LCD_DATA

P2-4

LCD_CLK

P2-5

LCD_CS

P2-6

LCD_RES

P2-7

LCD_BL+

P2-8

LCD_BL-

P2-9

+3.3V

P2-10

BUTTON

P4

P4-1

NC

P4-2

NC

P4-3

NC

P4-4

NC

P4-5

NC

P4-6

NC

P8

P8-1

ISO_VCC

P8-2

Throttle In

P8-3

Throttle Out

P8-4

NC

P8-5

ISO_GND

P8-6

NC

P8-7

DCHG-A

P8-8

DCHG-B

P8-9

CHG-A

P8-10

CHG-B

P8-11

LOCK_IN

P8-12

LOCK_OUT

P3

USB Connector to PC

N5

B-

N6

CHG-



connection / power-up sequence:

1. connect BAT- power cable
2. connect CHG- power cable
3. connect LCD, temper sensors, switch
4. connect 
No.1 JST-connector of battery test lines which starts with cell1 V- (which is same as BAT-)
5. if there are more than 12 cells connect second JST-connector of battery test lines which ends with the last cell + which is same as BAT+ (e.g. V20+   for a 20s pack)
6. turn on BMS switch
disconnection / power-down sequence
1.turn off BMS switch
2. if there are more than 12 cells disconnect second JST-connector of battery test lines which ends with the last cell + which is same as BAT+ (e.g. V20+   for a 20s pack)
3. disconnect first JST-connector of battery test lines which starts with cell1 V- (which is same as BAT-)
4. disconnect LCD, temper sensors
5. disconnect DCHG- power cable
6. disconnect BAT- power cable

Protection concept

OV/UV Protection
There are two OV/UV thresholds:
"CHG Limit" and "Over VOL"
"DCHG Limit" and "Under VOL"
The concept of using these parameters is as follows:
If the voltage of any cell reaches the thresholds "CHG Limit" or "DCHG Limit", the CHG FET or e-lock/throttle respectively will go off - the BMS will stay in normal state and will not issue an alarm.
If the voltage of any cell reaches the thresholds "Over_VOL" or "Under_VOL", the CHG FET or e=lock/throttle respectively will go off - the BMS will change to emergency state and will issue an OV/UV alarm as long as the limit violation persists.








Figure 
2 OV/UV State machine

Table 2 Description of states (see Figure 2)



State

Description

normal voltage

No OV, UV event; Permit charge, discharge if no other protection events

high voltage

Prohibit charging; Permit discharge if no other protection events; if discharge current exists, that is discharge current < discharge state threshold, turn on CHG FET

low voltage

Prohibit discharge, When pre-charge function is enabled, if V_cell < UV threshold, permit pre-charge but prohibit charge; if V_cell ≥ UV threshold, permit pre charge and charge if no other protection events; When pre-charge function is not enabled, prohibit precharge but permit charge if no other protection events; If charge current exists, that is charge current > charge state threshold, turn on discharge MOSFET

over voltage

same as high voltage; issue alarm

under voltage

same as low voltage; issue alarm




Table 3 Description of states (see Figure 2)

Transition

Initial State

Final State

Condition

1

normal 

voltage

high 

voltage

HV event occurs (V_cell  HV threshold & delay timer expires)

2

high 

voltage

normal 

voltage

HV event clears (V_cell < HV release value & delay timer expires)

3

normal 

voltage

low 

voltage

LV event occurs (V_cell ≤ LV threshold & delay timer expires)

4

low 

voltage

normal 

voltage

UV event clears (V_cell > LV release value & delay timer expires)

5

high 

voltage

over 

voltage

OV event occurs (V_cell  OV threshold & delay timer expires)

6

over 

voltage

high 

voltage

OV event clears (V_cell < OV release value & delay timer expires)

7

low 

voltage

under 

voltage

UV event occurs (V_cell ≤ UV threshold & delay timer expires)

8

under 

voltage

low 

voltage

UV event clears (V_cell > UV release value & delay timer expires)


There are two situations that BMS "think" the battery is fully charged one of the cell reaches CHG Limit

but charging in CV state,charging current will be lower and lower, when charging current reaches CHG current

OC Protection

The concept of using 'Max_Continue_I', 'Pulse_Current Permit Time' and 'DCHG_OC' is explained in the following example:

settings: Max_Continue_I = 150A; Pulse_I Delay = 10s; DCHG_OC = 300; CHG_OC=30

If I_bat (discharging)<150A,e-lock/throttle is on

If 150A ≤ I_bat (discharging)< 300A, e-lock/throttle will go off after a delay of 10s; State shows 'OC'

If I_bat (discharging) ≥ 300A,e-lock/throttle  will go off immediately (<10us); state shows'OC' or short

If I_bat (discharging) ≥ 30A,CHG FET will be off immediately


LCD


1st page:SOC,real-time current,total voltage,temperature,alarm info(OV,OC,OT,UV)

2nd page:voltage of highest and lowest,4 channels temperatures,state of battery

3rd page:1-16 cells voltage

4th  page: capacity of pack,SOC,SOH
















Name

description

limits [unit]

remarks

Cell 1-24

display the real time cell

voltages as well as OV/UV

status and balancing status

+5.399 [V]

the dots to the right turn red when bleeding of this cell is on.

Bleeding starts with a delay of approx. 5min

Total Voltage

displays actual battery pack voltage

+130.0 [V]

Current

displays actual battery pack current

+300.0[A]

Pack 

Temp

displays actual battery pack temperature

+125.0 [°C]

-30.0 [°C]

external temp sensor

Sys Temp

displays actual battery pack temperature

+125.0 [°C]

-30.0 [°C]

internal temp sensor

CHG Enable

indicates charging mode

true / false

DCHG Enable

indicates discharging mode

true / false

Life cycle

displays the number of charge/discharge cycles

000

SOC

displays the State of Charge of the battery pack

State

displays the system's state

Discharging/Charging/ (Standby/OV/OC/OT/UV/Short/)






Parameter Settings

Name

description

range [unit]

action if threshold is exceeded

CHG Limit

sets the maximum 

cell voltage

0<V≤5'000 [mV]

switches off CHG-FET

CHG_Recover

sets the reset voltage of the 'CHG Limit' state

0<V≤5'000 [mV]

switches on CHG-FET when the

 'highest' cell returns to the 

CHG_Recover threshold

CHG_Stop_Cur

sets minimum charge current

0<I≤5'000 [mA]

switches off CHG-FET after 

xx seconds

DCHG Limit

sets the minimum cell voltage

0<V≤5'000 [mV]

switches off throttle & e-lock

DCHG_Recover

sets the reset voltage of the 'DCHG Limit' state

0<V≤5'000 [mV]

switches on throttle & e-lock

Max_Continue_I

sets the max discharge current

0<I≤200'000 [mA]

Pulse_I_Delay

max. duration of pulse current

1<t≤30 [s]

DCHG_OC

sets the pulse current

switches off CHG- and throttle & e -lock and triggers OC alarm

CHG_OC

sets the max charging current

switches off CHG- and throttle & e-lock and triggers OC alarm

Difference_On

sets the max cell voltage difference ('highest' against the 'lowest' cell) at which bleeding begins

0<V≤2000 [mV]

bleeding of high cell(s) begins

Difference_Off

sets the min cell voltage difference at which bleeding stops

0<V≤2000 [mV]

bleeding of high cell(s) stops 

Active_On

sets the min cell voltage to start bleeding

0<V≤5'000 [mV]

bleeding is enabled

Stop Balance Temp

sets the max Temperature of internal temp sensor

0<T≤70 [°C]

stops bleeding

Over_VOL

sets the maximum cell voltage

0<V≤5'000 [mV]

switches off CHG-FET and triggers OV alarm

Under_VOL

sets the minimum cell 

voltage

0<V≤5'000 [mV]

switches off throttle & e-lock and triggers UV alarm

OC Limit

sets the over current 

(peak current)

0<I≤300 [A]

OT Limit

sets the max Temperature

 of external temp sensor

-20<T≤80 [°C]

switches off CHG- and throttle & e-lock

 and triggers OT alarm

OT_Recover

sets the reset 

Temperature of the OT

 alarm state

50<T≤70 [°C]

switches on CHG- and throttle & e-lock

UT Limit

sets the min Temperature 

of external temp sensor

-20<T≤80 [°C]

switches off CHG- and throttle & e-lock

 and triggers UT alarm

UT_Recover

sets the reset 

Temperature of the UT 

alarm state

50<T≤70 [°C]

switches on CHG- and throttle & e-lock

Design Capacity

sets the nominal capacity

 of the battery pack

0<mAh≤500'000 [mAh]

enter manufacturer value

Current Capacity

sets the estimated initial 

capacity of the battery 

pack

0<Ah≤500'000 [mAh]

is dynamically adjusted according to 

real SOC. enter only once!!

SOC<

sets the min SOC 

0<SOC<100 [%]

activates the BMS throttle limiting signal

 and issues a low power alarm

Capacity Setting


Capacity Setting is divided into two values, the 'Design Capacity', which is set to the nominal capacity of the battery pack and the 'Current Capacity', which is set to an estimated value of the battery pack's initial charge before connecting for the first time. After a number of charge and discharge cycles, the BMS will 'learn' the real SOC and will adjust these values automatically. You must not set these two parameters after the initial setup.


Cell Balancing


The concept of using "Difference_On" and "Difference_Off" is explained in the following example:


settings: Difference_On = 50mV ; Difference_Off = 30mV ; Active_On = 3'000mV


behaviour: if any number of cell voltages are at least 50mV higher than the lowest cell (i.e. Difference_On) and this lowest cell's voltage is higher than 3'000mV (i.e. Active_On), the BMS starts bleeding all 'high' cells (i.e. those above this 50mV threshold).


When all 'high' cells have reached a voltage 30mV above the lowest cell (i.e. Difference_Off) bleeding will stop


.


Tools

Name

description

range [unit]

remarks

First Chip

sets the number of cells connected

to the BMS via the first JST connector

4-12

Second Chip

sets the number of cells connected

to the BMS via the second JST connector

0 (if not used) or 4-12

BEEP ENABLE

Sets beep on/off

Current Adj

sets the calibration factor for

the current sensor

factory set!

'config2' shows

the hall sensor

voltage in [mV] 

see 1)

Center Voltage

sets the offset for the current sensor

factory set!

Speed setting

Function not enabled yet!

Milage

Function not enabled yet!


Follow these steps to calibrate the current sensor (CS):


1. Run a cable connected to a constant current source in the range of 20A to 50A through the CS. A battery charger could supply the current. If the current is too low e.g. only 2A, you can wind the cable 10 times through the CS to reach 10x2A= 20A. Make sure the current flow direction is correct i.e. the arrow on the CS indicates the discharge direction from the battery.

2. switch off the constant current and confirm the BMS is in 'standby' state i.e. neither charging nor discharging.

3. copy the value displayed in 'config2' (approx. 2470-2500mV) to the 'Center Voltage' field and click 'Step1'.

4. Switch on the constant current and measure it with an amp meter.

5. copy the amp meter reading in [A] to 'Current Adjust' field and click 'Step2' to complete the calibration.



Possible configurations for cell numbers assigned to chip1 and 2


cells

chip1:chip2

comments

24s

12:12

23s

12:11

22s

12:10

11:11

21s

12:09

11:10

20s

12:08

11:09

10:10

19s

12:07

11:08

10:09

18s

12:06

11:07

10:08

09:09

17s

12:05

11:06

10:07

09:08

16s

12:04

11:05

10:06

09:07

08:08

15s

12:03

11:04

10:05

09:06

08:07


Electrical connections BMS pins and battery cells

Cells are stacked in the Pack and numbered from low to high i.e. Cell 1 is always the first cell which negative end is at the same time the negative end (minus pole) of the pack. In a 20s pack Cell 20 is the last cell and its positive end is the positive and of the pack (plus pole).

Each cell's negative and positive end is connected to the BMS via a single balancer cable which is used to measure the voltage and to draw some discharge current from each cell. Since all cells are stacked only one cable is required for any cell's positive end and the negative end of the successive cell.

The voltages in the pack are designated Vn_neg (negative end of Cell n, for short Vn-) and Vn_pos (positive end of Cell n, for short Vn+), there for Vn_pos = V(n+1)_nege-bike BMS

comments: nc = not connected; red text = pay attention

For 13s and 14s battery packs continue the same scheme as indicated in the table above

For 4s to 12s battery packs use only first chip following the same scheme as indicated in the table above



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