Wednesday, August 12, 2015

New Battety Technologies

As we all know, Motor rating is fixed, and only thing that affect the eBike or car range is, BATTERY.

Yeah, but battery technology improving these days due to intense researchs,

Conventional Batteries (we're using, also in production) : 
Lead acid battery
Li-ion battery
Li-ion Cells
LiPo (Lithium ion-polymer)
Li-ion phospate

Capacitor type batteries :

Upcoming (will be launched soon) :
EEStor -
Sakthi3 -
StorDot -


Supercapacitors store 2700 F, and charge in few seconds, but only contraint is weight, 15w-50w/kg

Ultrabattery Lead acide battery and supercapacitor hybrid is ultrabattery, that is it improve the lifecycle/efficiency of lead acid battery, also improve faster charging/discharing.

Supercapacitor specification :
Maxwell BCAP3000P 3000F 2.7V Super Farad Cap Ultra Capacitor

Capacitance  3000 farads
DC Equivalent Series Resistance (ESR) 0.29 milliohm
AC Equivalent Series Resistance (ESR) 0.24 milliohm
Leakage Current 5.2 mA
Operating Temperature Range -40°C to +65°C
Stored energy 10944 joules (3.04 WH)
Max Power 3020 Watts
Connections M12 x 1.75 threaded stud
Weight .89 lb (405 grams)
Diameter 2.4 inches (61 mm)
Height (including studs) 6.53 inches (130 mm)
Stud diameter .55 inches (14mm)
Stud height .120 inches (3 mm)

Normal Lead acid and Lipo batteries capacity calculated in Ah, V
Capacitors /Supercapacitors capacity calculated in Farad

Fard to Ah conversion (for theorital understanding only):

In Lead acid battery, even after discharge, it keep the voltage same, but in capacitor half discharge means, voltage also reduced by half.

Tuesday, August 11, 2015

Cooling of Motor and MOSFET

Due to the heavy current flow in Motor stator winding and MOSFET, there is a possibility of damage beyond certain temperature, so we have to cool it to maintain below optimal temperature.

This cooling is done in the price of reduced range, yeah we're using the power for cooling equipments from same battery, better we have to use the temperature sensor data to ON/OFF the cooling equipments, if we kept the cooling equipments always ON means, resulting in low range of eBike.

Which equipmets need cooling :
Mosfet, due to high speed switching / regenerative braking / high current flow, the temperature increase suddenly, so we must need cooling.

 Motor stator coil, as we supply the power in the stator coil, due to copper loss/eddy current loss, stator coil temperature also increase suddenly, so we have to keep this also cool.

High speed (above 40 kmph) reduce the range of eBike so it drain the battery faster, also it increase the copper losses at high rpm, so if we kept eBike in optimal speed means, More range, safety to our equipments too without the need of cooling.

Cooling technique for Mosfet :
Air cooling - Simply placing a CPU fans in controller box keep the temperature of circuits under control or within the preset level, Fan is fitted in heatsink, or we have to increase the surface area of heatsink, that is we can easily increase the surface area by placing aluminiu rectangular metal pack, so due to large surface area it grab more heat from the heatsink, and keep the circuits cool.

Water cooling - 
For water cooling, we need to remove heatsink and place the water cooling small equipments, and we have to keep the water flow.


Cooling technique for Motor :

Air cooling using CPU Fan - Put a hole in motor case/shield and place the CPU fans there, so it reduce the temeprature of stator coils.

Air cooling using Mini compressor - Chinese made mini compressors are available, they're operating at 12V 150W, which are mainly created for small refrigerators in car for keeping beer cans cool, we can use this mini compressor to generate cool air (in range of 20 degress celcius), so it cool the coils.

Air cooling using mini compressor with Vortex Cool Tool Cold Air Gun Spot Cooler - Spot coolers are popular, as these cool they cool in rapid manner.

Water cooling - creating a water path, and run by a small pump like we do in cooling engine in car.

In Progress, Will Update ...!

Saturday, August 8, 2015

Input Stage of BLDC Controller

Input stage consist of rs232/USB and Microcontroller, we need to connect the rs232/USB to external interface to load the code into microcontroller.

Input stage :
  1. PCB work
  2. Coding the Microcontroller unit

In Progress, Will Update ...!

Output Stage of BLDC controller

As output stage of the controller grab the source power (from Battery) and supply to the load (Motor), so i planned to design the Output portion first.

Output stage componets :
IGBT drivers
Current sensors.
Thick Busbar / Thick Soldering for connecting the Mosfet output to the Motor phase leads.

Output stage Circuit :
Full bridge
Double Puse test.

What is MOSFET ?
MOSFET is the 3 terminal/lead electronic device, terminals are Source(S), Gate (G), Drain (D)

Mosfet is just a switch, but it ON only when the Signal/voltage given in Terminal G (gate),
if the gate signal is given to Mosfet, it start conducting that is, it supply the power connected to Terminal S (source) to the Terminal D (drain)

 P type Mosfet Symbol

Figure shows Terminal 'S' connected to Battery, Terminal 'D' connected to Motor phase, Terminal 'G' connected to IGBT driver

Example :
Battery is connected to the Terminal S (source) of MOSFET,
Motor is Connected to the Terminal D (drain) of MOSFET,
IGBT Driver is connected to the Terminal G (gate).

[ON] Once the Signal/Voltage from IGBT Driver is given to Terminal G, Current flow occurs from battery to Motor.

[OFF] If no signal/voltage given  from IGBT Driver to Terminal G, NO Current flow occurs from battery to Motor.

Practical Mosfet :
theoritically, if we removed or stopped the supply to the Terminal G (gate), then terminal S (source) to Terminal D (drain) become open (no conduction), but this is not happening preactically, see the below video

For ON we need to give signal/supply to the Terminal G, for OFF even after removal of gate signal still MOSFET conduct, so we need to ground the Terminal G, then only it stop conduct.

How many FET going to use ..??
It is one of the important question regarding controller. In single controller we're going to use "Full Bridge" circuit, so the numbers must be like 6, 12, 18, 24 FET (multiples of 6 is the simple rule).

I planned to use 6 FET for my controller, as it is the minimum one.

Per MOSFET power dissipation :

MOSFET name and number :

Current Sensor :
Once we accelerate the bicycle using throttle, then the current flow increases, sometime it may damage the controller and motor, as they have certain limit, if it crossed the limit, then they damage, so we have to measure the current flow in phase wires (between controller and motor), and using the current sensor, and supply the measured current value to microcontroller, as we already store/programmed the certain current limit, so microcontroller compare the realtime current flow in phase wires with the preset limiting value, if it cross the preset current limiting value, then Microcontroller stop the signal to MOSFET, once the current flow value is below the preset value then it automatically turn ON.

Buck Converter :
BLDC motor is powered by battery in which controller sits in center between baatery and motor, but electronic components in controller also need a electric supply (in few 5v to 12v), so to stepdown the volatage we need a Buck converter.

Double Pulse Tester :
To know the switching characterisitics of MOSFET for our setup, we need to do one test called "Double Pulse Test", using this test we can understood more about the MOSFET temperature for certain current value and all, it is something like simulation without original load (motor)


Choosing the Components :

MOSFET Choosing :
Choosing MOSFET for controller depends on peak current and peak voltage, if we used the less rating MOSFET means, due to power dissipation overheat, it simply burns, so we always have to choose the higher rating MOSFET.

IRFP4110 - 100 A , 100 V,  Download datasheet
IRFP4468 - 190 A , 100 V, Download datasheet

We can decide from above mosfet ratings, still lot of high rating mosfets are there for higher power vehicles like car/bus/truck, but thing is higher power MOSFET need a proper cooling.

IGBT Driver Choosing :

IRS2186 - 

Current Sensor choosing :  

ACS758 -

Buck Converter choosing :

LTC3638 -

In Progress, Will Update ...! 

Thursday, August 6, 2015

Choosing the Motor and Battery for controller design

For designing the controller, we need the motor rating and battery voltage.

Requirements :
Speed : 40-50 mph.
Battery undervoltage Protection :
Current Limiting :
Method : PWM (Pulse Width Modulation)
Assumption : 30-35 Wh per Mile.
Motor : 48V 2000W
torque :  (still dont know how much i need, have to study)

For calculating rpm  (still have to analyse):

Motor rating : 48V 2000W , Sensored
From videos seen in youtube, 2000W or 3000W BLDC motors are doing good speed, but as this is my first project so i choosed 2000W, as our area have big slops/terrain.

Choosing Battery :
There are 2 choices in battery 'Li-ion cells' and  'Li-ion Polymer',
but Li-ion Polymer have lot of advantage over Li-ion batteries, like less weight, quick charge, high discharge current comparing to Li-ion cells battery,but in price point of view Li-ion cells are cheaper.

Li-ion cells :
Li-ion batteries are available in big block shape (we're using that in home UPS system) and Li-ion Cells
Tesla cars even use Li-ion cells.

Li-ion Polymer (LiPo) :
Lithium ion Polymer (LiPo) batteries are used for Ebikes mostly due to it's high peak current, Li-ion batteries are specified in 'C' and 'S' Value,

C means, Continuous, 
if battery show 40C means, we can grab maximum 40 A continuously.

S means, Series,
If battery shows 3S means, 3 cells are connected in series, that is 3.7 V  x 3 cell = 11.1 v .
 Li-ion Polymer battery is created by series joint of cells, each cell voltage is 3.7v

mAh  means, milli Ampere hour,
If battery shows, 4000 mAh means, its capacity is 4000 mAh or it can store 4000 mAh. 

Example :
Battery Specififcation :16 Ah 22.2V

For more detailed thing about battery (highly useful) :

Battery Fuse :

Budget wise :
High budget (use LiPo), Low budget (use Li-ion cells)


Range Calculator :
Range is one of the important factor to consider in creating an ebike, if we use ebike for home to office, then back to home. we have to calculate the per day usage kilometer or Miles, and adding extra Kilometer, so we may use it for other works too.

Eg :
Home to Office distance = 10 Miles (16 Km) , to and fro distance is 20 Miles,  so we have to create ebike range greater than 20 Miles, say 25 or 30 miles will be better .

Range =  Number of batteries  x Capacity of single battery (in Ah) x Voltage of single battery (in V)
                                                          Per Miles Watt usage

Per Miles Watt usage vary depends on speed, so we have to assume it as 35-50 Watt per Miles

Eg :
So assume Per watt Miles as 40 watt
i have 5 batteries of 26000 mAh , 22.2V ,
convert 26000 mAh to Ah, just divide by 1000, so 26 Ah.

Range  =  5 x 26 x 22.2    

          =  72.15 miles

according to your need, you can increase or decrease the number of batteries.

Weight :
For Low weight (use LiPo), weight is not a matter (use Li-ion cells)

 if we're going to use in bicycle/motorbike/car means, little extra weight is not going to affect a performance, so Li-ion cells is enough, still LiPo give less weight.

 but if you're going to use in helicopter/mini aeroplane/Drone, then weight matters, so LiPo is the only choice.

Example :
For Li-ion Polymer , 16000 mAh 6S1P 22.2V - Weight : 1932 gram.
think i am using 3 batteries,
3 battery total capacity in watt = 3  x 16 x 22.2 = 1065.6 W = 1.065 kilowatt

3 battery weight in gram = 3 x 1932 gram =  5796 gram = 5.796 kilogram.

 so  5.796 kg battery store 1.065 kw,

1 kg of LiPo batteries store    = 1.065/5.796   =  0.1834 kw
1 kw of Lipo batteries weight  = 5.796/1.065  =  5.442    kg

Now same calculation for Li-ion cells.
For Samsung ICR18650-26F cells , 2600 mAh, 3.7V - Weight : 48 gram.

think i am using 110 cells,
110 cells total capacity in watt = 110 x 2.6 x 3.7 = 1058.2 W
110 cells weight in gram = 110 x 48 = 5280 gram

so 5.280 kg of  cells store 1.0582  kw

1 kg of Li-ion cells store  = 1.0582/5.280   =  0.20 kw
1 kw of Li-ion cells store =  5.280/1.0582 = 4.989 kg

but thing is packing  of 110 cells need a special battery pack, have to weld, and connecting wires, charging of this 110 cell, these constraints increase the overall weight of the battery pack, resulting in LiPo the winner in weight range.

What i choosed :
16000 mAh 6S1P 22.2V

Range  =  1 x 16 x 22.2    

          =  8.88 miles
 as i use very less, so choosed only single battery.


Number of cells/power needed :

Li-ion cells  18650  2600 mAh 3.7V : 
Theoritical calcualtion :
10s 10p = 26.0A 37.0v,  0962.00W, 4800 gram, 100 cells.
11s 11p = 28.6A  40.7v, 1164.02W,  5808 gram, 121 cells
12s 12p = 31.2A 44.4V, 1385.28W, 6912 gram, 144 cells
 Practical values :

Li-ion cells 18650 6000 mAh, 3.7V :

10s 10p = 26.0A 37.0v,  0962.00W, 4800 gram, 100 cells.
11s 11p = 28.6A  40.7v, 1164.02W,  5808 gram, 121 cells
12s 12p = 31.2A 44.4V, 1385.28W, 6912 gram, 144 cells

In Progress, Will Update ...! 

Designing an Ebike BLDC Controller from Scratch

hi guys,
i am noob in this field, planned to design Ebike controller from scratch , why i choosed Controller is, because controller is the heart of the ebike, other parts can be bought easily with our needs, but controller is costly and most doesn't fullfil our needs.

 First i try to understand the controller and its components, without knowing the details and starting a PCB work is like learn swimming in centre of the pacific ocean, so i am always try to explain everything in brief, so noob like me can easily understood.

Name      : 6 FET BLDC Controller
Target     : Simple Ebike controller for BLDC motor (Brushless DC motor)
Motor      : 48V 2000W
Battery    :  1 x 10000 mAh 6S1P  25C 22.2V

Deadline  : 1 year (within August 2016)

From my view, Ebike controller or Controller  for BLDC is common to all, example if we developed one model successfully then we can use it in ebike, cycle, motorbikes, car and lot of application, so we have to progress slow and steady.

Google helped me a lot, and what i understood is, Controller consist of input and output.

Below figure show the components which connect to controller.

Throttle : we increase/decrease the ebike speed using the throttle , which is connected to input of Controller.
Cycle Analyst : it display the speed, temperature of motor, current values, which is connected to input of the controller. (because temperature of motor are got from tememperature senor, which is connected to input of controller)
Battery : it supply the power to the motor, which is connected to the output of the controller
Motor : it is the load, sensorless 2000W BLDC
Temperature sensor : it have to be fitted inside the motor, so we can view the temperature of motor in cycle analst display

Image 2 :

BLDC Motor consist of 7 wires, they're
3 wires for phase,
3 wires for hall sensor,
1 for temeprature sensor we fitted in it.

3 hall sensor wire and 1 temperature sensor wire is connected to input of controller.

Imgae 3 :

 In above figure, all 3 pahse wires of motor (U, V, W) is connected to the output of the controller, as current flow in both direction because of regenerative braking, so we used the double side arrow.

 Image 4 :

 In above image, battery is connected to the output of the controller.

Image 5 :

in above image, throttle is connected to the input of the controller, and cycle analyst is connected to the controller.

Image 5.1 :

Brake signal or voltage needed for regenerative braking, so it must connect to the input of controller and fuse (between controller and battery) is must to protect the controller and motor from overcurrent.

Till now i understood about the components of ebike and its connections, now let us move to the controller.

After lot of search on goolge and read from lot of  sites i understood few more things about controller.

In Electronics they're two type of devices/components
1) Active device
2) Passive Device

Active Device change the signal/current by amplification. example : transistors, op.amp

Passive devices change the signal/current by attenuation. example : resitor, capacitor, inductor.

still i not understood lot of these, but i will try to learn and post here, so it may helpful for others.

Here In our schematic, we discuss about "Active devices" only first, once we finalised the active devices, then we have to find a way for passive devices and values.

Image 6 :

Controller input unit :
Input unit consist of rs232/usb and microcontroller.

Microcontroller :
Microcontroller process the hall sensor input data we given and give signal to MOSFET through IGBT Drivers.

rs232/usb :
Microcontroller process any amount of data, but for processing we need to program the microcontroller, for that we have to connect rs232/usb to computer or some external interface to load the program codes into the microcontroller.

Controller output unit :
Contrller output consist of IGBT drivers, Mosfets, Current sensor.

Mosfets :
Mosfets is just a switch , but it can switch at a speed of  20 khz and above.
Battery and BLDC motor is connected through Mosfet that is, mosfet control the voltage/current flow from battery to Motor by switching. (we call as switched mode power supply). When to switch ON and when to switch OFF the Mosfet was guided by Microcontroller through the IGBT drivers .

IGBT driver :

Microcontroller decide when to switch ON and OFF the MOSFET and give signal, but the signal current is very low in milliampere (mA) so if we pass the microcontroller signal directly to MOSFET means, due to low signal current, MOSFET switching speed will be very low and switching loss become high, so we use the intermediate circuit called "IGBT Drivers" to amply the current , and then given to the MOSFET, so MOSFET work smoothly in high switching speed.

Current Sensor :
 If the output current from MOSFET crossed certain limit means, Motor will burn or MOSFET will burn, so we have to limit the current values. For limiting the current value first of all we must know the exact current flow through the MOSFET , so we need a current sensors, which give signal to the Microprocessor, which compare the current wuth pre-set value, if it crossed the pre-set value it shutoff the MOSFET, once the current value in less then the pre-set value the it automatically on the MOSFET.

First i planned to start output portion of controller, because Input portion is related to coding, but without the values of output stage we wont code, so i am starting from output portion.

In Progress, Will Update ...!

Welcome to Ebikecontroller

i am very new to this ebike field, due to my own interest i started to thinking about ebikes and planned to create controller from scratch.

My learning things about controller is Documented in this blog fully, so please read all posts. it will surely help newbie to understand controller.

How the interest came ?
I am from India and always i try the new technologies, just like that TVS (one of motorbike company in india) announced about launching "TVS Qube", but more than 3 years, they not launched it.

TVS Qube is a hybrid 2 wheeler (scooter) which work on petrol as well as electricity stored in battery, i dreamed it to buy one, but that delay caused me to think "whyn't you can develop one ..??" then i started searching in internet about hybrid and electric ebikes, this way i concentrated more on eBikes in my free time.

After a small research, i planned to build eBike (bicycle with electric powered one wheel), that is we have to replace rear wheel by hub motor fitted wheel.

Parts needed for Ebike :
  1. One Cycle (mountain ranger or one with good front/back suspension is needed)
  2. 48V 2000W BLDC Hub Motor (with sensor)
  3. Rear rim with high gauge spokes (we have to Lace the hub motor in it) and Tyre.
  4. Lipo Battery (2 nos)
  5. BMS (Battery management system) so we can charge battery
  6. Throttle (to control the present speed like we do in bikes)
  7. On/Off Switch
  8. Cycle analyst (that display speed/battery current/temeperature and all)
  9. Controller.

i thought, we can buy this and assemble it, finish, but here the problem start, we can buy everything, except controller, because all the controller available here are only for 250W BLDC motor, but i planned to create for 2000W, so if i got the controller means, Project finished, but controller...????

thats why i created this blog about creating controller from scratch, i planned to use my free time for creating the controller circuit.