Solar Bicycle Overview

Bicycles are the most common and most numerous (> 2 billion) vehicle amongst any kind of vehicle whether human powered or motorised ever produced by mankind. Invented over 2 centuries back (by the German Karl von Drais in 1817), today we see a major transformation - solar bicycles. 

Currently, solar bicycle is the only electric vehicle that provides a fully sustainable, environmental friendly, motorised solution to one's travel needs (upto 25 kms per day). 

Go cycling! Roam the remote country side! Venture out to areas where there is no access to electricity or petrol pumps! Go where no man has gone before with a Solar Cycle!

Truly Sustainable Living: Be totally off fossil fuels and electric grid. Zero running cost. Travel upto 25 kms/day  with a 40W panel attached to your cycle. Use Solar. Save Mother Earth!

No Registration or Driving License required: Can't get a driving licence for your under 18 teenager? Current regulations state that those between the age of 16 to 18 can obtain a license for driving a 2-wheeler with engine capacity less than 50 cc. Many teenagers aged 17 years or less are observed to be illegally riding a registered vehicle, with engine capacity of 100 cc or higher, at high speeds contributing to higher rate of accidents on Indian roads.  Best answer is to ride to school with an environmentally sustainable solution - a solar bicycle - whose speed is limited to 30 km/hour. 

Bicycle to Work: Wish to make a transition to a healthy lifestyle? Don't have time to go to a gym?  Ride a Solar cycle to work. Can choose between manual pedalling, power assisted pedalling, or full power throttle without pedalling with a solar bicycle.  

Bring Your Own Panel: As the BYOD (Bring your own device) policy is becoming more popular, carrying your own panel to work has even more advantages. No need to search for a charging point at work. Simply park the vehicle under the Sun and the battery will silently get charged while your work. 

Safety First: In sharp contrast to a fast charging process from the electric utility's ac mains that has resulted in numerous vehicles catching fire, the solar charge process is an safe and elegant one that is also gentle on the batteries and enhances its life too.

Charge while you ride: Keep the Solar charger switched ON while you ride along with your panel. The solar panel will supply approximately 15 to 20% of the BLDC motor's  needs while you ride. This means that the battery would be supplying only 80 to 85% of the energy and thus getting drained less, again enhancing the battery life. This also means that you can  cover larger distances after a full charge.  

Pedal your way back: Run out of battery power? Unlike other e-vehicles you do not get stranded in the middle of nowhere. Pedal back home.

Low Loss / High Efficiency Charging Process: When you charge the battery from a 230 Volt ac electric mains, an AC to DC conversion takes place which is inefficient. This means high temperature - low reliability operation, or requirement for forced cooling or bigger heat sink for the charger.  Many AC to DC chargers are also seen to inject harmful harmonics into the AC system.  Unlike this, the Solar to Battery charge process is DC to DC which is more efficient, which means that the charger can be smaller in size, more reliable, no need for cooling fans, less noise, etc. 

Optimum Charging Process: Unlike other chargers, the solar charger is microcontroller based and intelligent. The ARM controller chooses an optimum - Maximum Power Point Tracking (MPPT) point for the DC to DC (Solar to Battery) conversion for efficient charging with a smaller solar panel that can be carried on a bicycle. 

Charge in the Parking Lot Under the Sun: Staying in an Apartment or an Upper Floor? With Lithium Batteries getting placed inside the bicycle frame it becomes more and more difficult to charge the battery from an electric ac mains point; the entire bicycle needs to be lifted to the Apartment. Unless, you opt for the far more convenient alternative solution - Solar charging in the parking lot under the Sun!

Unique E-vehicle: No other E-vehicle other than a Solar Bicycle can boast of all or any of the above unique features!

Low Cost to Upgrade your E-bicycle: Riding your e-bicycle without solar upgrade is not truly environmentally friendly. The BEM Solar upgrade kit for  ₹2700 (inclusive of GST) gives you the satisfaction that you are doing your bit to save the environment.  

BEM® Solar-Bicycle Description

The BEM® Solar bicycle is different from all other electric vehicles with respect to its charging needs.  The Solar bicycle does not need to be plugged into an electric socket for charging!  No need to hunt for an electric socket at your destination or place of work. Simply park the bicycle with the solar panel facing the sun for approximately 6 hours to recharge the battery of the e-bicycle after  20 kms of daily travel. 

Harness solar energy even while travelling. During day travel, the DC motor of the Solar bicycle usually draws only 80% to 85% of the total current requirement from the Li-ion battery while the Solar panel supplies the rest (15% to 20%). Reduced burden on the battery means longer life of the battery.  The slower charging process over 6 hours under the sun is also recommended to enhance the battery life. (In sharp contrast, fast charging from electric outlets reduces battery life). 

Looking for a low loss charging solution for your E-bicycle? A 230 Volt AC to DC conversion is inefficient. Introducing the higher efficiency DC to DC (Solar to Battery) conversion with Maximum Power Point Tracking (MPPT) for faster charging with a smaller solar panel.   

The BEM Savitre charge controller is a 2 Amps (Max.) Solar True Maximum Power Point Tracking (MPPT) algorithm based charger for 37 Volt (Nominal), 42 Volt (Maximum) Li-ion battery. This charger provides you with the ability to extract the maximum possible power out of your Solar panel of rating 12 Volt, 40W, and feed it into the  rechargeable Li-ion battery. This means that the E-Bicycle battery would get fully charged in the shortest possible time with a smaller sized (lower cost) Solar panel.  Recommended size of solar panel is 12V, 40W that can be easily fitted on the rear carrier of a standard bicycle 

Set-up is easy as well. Simply, plug your solar panel into one (input) side of the solar charge controller and your e-bicycle battery into the other (output) side, then Switch ON the charger and the battery would start charging at the fastest rate! Ensure that the solar panel is facing sun, avoid shadows, and keep the panel surface clean for best performance.   

BEM® Solar E-Bicycle Kit Description

The BEM® Solar E-Bicycle Kit (DIY) helps you convert your e-bicycle into a solar cycle.  The Kit does not include two essential or mandatory components, namely - (i) an electric bicycle with Li-Ion battery and (ii) a 12 Volt,  40 Watt Solar Panel.  In this manner, the customer is not restricted on his/her choice of bicycles and solar panels. 

The kit consists of a BEM® सवित्रे™  Savitre E-Bicycle Battery Charge Controller, a rear Bicycle Carrier for 26" MTB E- Cycle, an aluminium alloy Centre Stand, and also a few rods and fittings for 40 W Solar Panel. 

About the Charger

The BEM® सवित्रे™  Savitre - 2 Amps MPPT  Solar Charge Controller consists of MPPT digital controller and photovoltaic drivers and is designed to control high efficiency DC/DC conversion used in photovoltaic based Li-Ion battery charging application.

Savitre is a true MPPT solar charge controller in the 2 Amps range unlike others.  (Almost all the  solar charger modules available in the market  are actually PWM controllers that operate at a fixed 12 V input voltage and not at the MPPT of the solar panel. Then there are others such as the 'CN3791 MPPT Solar Charger Module' that claim to be MPPT controllers  but actually operate at a fixed input voltage such as 16V regardless of the maximum power point (MPP) of the solar panel).  

If the battery voltage is very low, a slow charge current is applied and limited until the voltage rises above a pre-set threshold value Vt. The full charge current is then applied. Once full charge is detected on the voltage of the battery, the system switches to a floating charge and maintains the battery voltage at a fixed threshold. At any time, the system will run in MPPT mode if the available power is lower than the power required to achieve voltage or current regulation.

Savitre is a  Maximum Power Point Tracking (MPPT) solar charge controller for 12-V solar panels. This compact reference design targets medium power solar charger solutions and is capable of operating with 12 V solar panels, 37V Nominal (42V Max) Li-Ion batteries and providing  upto 2 A output current. The design uses a boost buck converter to step up the panel voltage to the battery voltage. The boost converter and its connected gate drivers are controlled by a ARM Cortex microcontroller unit (MCU), which calculates the maximum power point using the perturb and observe method. The solar MPPT charge controller is created with real-world considerations, including reverse battery protection, software programmable alarms and indications, and surge and ESD protection.

37 V Nominal, (42 V Max.) Li-Ion Battery

Vin range = 6V to 25V Vmp (21V Voc)

Max Input Current: Isc = 3 A

MPPT algorithm for optimized photovoltaic applications

Up to 2A charging current

Reverse current protection

Trickle charge and fast charge mode

Up to 80% converter efficiency

42.5V max charge voltage, 42V floating voltage

Model MPPT1v9

OUTPUT Connector 2.1 x 5.5mm DC Power Jack / Plug (Male)

• Operating Voltage (VDC) 12

• Operating Temperature (°C) -40 to 85

• Swithing Frequency (KHz) 50

• Maximum Charging Current (A) 2

• Length (mm) 90

• Width (mm) 80

• Height (mm) 60

• Weight (gm) 150

• Shipment Weight 0.2 kg

• Shipment Dimensions 15 × 12 × 6 cm