We are building an open protocol smart charger for lithium batteries. BatCha can charge BATMON enabled batteries without have to set the parameters for each battery. BatCha is WiFi enabled and monitors the charge against over-temperature, over-voltage etc. Charging using BatCha is extremely simple and dumb proof.

BATMON is a lightweight BMS for drone batteries. 

We launched a Kickstarter Campaign to build the charger https://www.kickstarter.com/projects/batmon/batcha-and-batmon-smart-charger-and-battery. Please donate and support our campaign.

Lithium ion batteries have a higher energy capacity than Lithium Polymer packs, in general. Higher capacity lithium ion packs can be designed if the current draw of the drones are known. We have built a web utility to find the right chemistry of cells to use, from among the hundreds of different cells. 

Input the max weight, and current discharge of the drone and see: 

• Battery cell configuration (number of cells in parallel and series) 
• Approximate flight time as compared to current aircraft (without weight change)
• Battery weight.

Reach out to us shout@rotoye.com to get free access to this utility. 

• v4 is super fast to install on most batteries with a tool, and connects to the balance leads.
• The modular board make it possible to reuse BatMon after end of life of a battery. The XT90 leads can be replaced if they are worn, but can practically be reused few times, reducing the cost overhead on each smart battery pack.

You can now buy BatMon enabled smart batteries off the website, saving you the engineering time for assembling your own. 

BatMon enabled batteries can talk with Ardupilot, Pixhawk, Arduino and ROS. BatMon enables safe and robust operation of robot using smart batteries. Batteries are currently shipped ground within contiguous United States.

Smart Battery features

• 2-12S LiPo/Li-Ion Battery support
• SMBUS based data protocol. Work out of the box with Ardupilot, Pixhawk*, Arduino, Raspberry Pi etc
• 150A burst/ Optional 240A burst
• Accurate current monitoring 
• Accurate individual voltage monitoring
• OLED screen for monitoring and outdoor viewing
• Buzzer usable for warning
• Firmware upgradeable with optional programmer

Buy Smart Battery 6S 4500mAh

Get custom BatMon enabled Smart Battery

We built BatMon for making smart batteries. BatMon can now talk with Ardupilot, Pixhawk, and ROS and enables safe and robust operation of robot using smart batteries. But there is a missing piece, a smart charger that can safely charge batteries with a peace of mind for customers.

So, we are building exactly that, and a lot more, to future proof your workflow as they scale. Below is a sneak peek of the most foolproof futureproof smart charger we know of: BatCha

BatCha features

• Opensource Firmware
• 2-12S LiPo Charge
• Smart battery data interfaces:
  • I2C: Two wire based protocol such as SMBUS
  • CAN BUS: Two wire differential pair robust protocol for UAVCAN, CANaerospace etc
  • LIN BUS : Single wire communication protocol for micro drones
• Two ports. Charge two battery simultaneously.
• 500 watt total power. Shareable to either ports
• Max charging current per port: 20A
• Measures battery temperature and voltage for safe charging limits for each battery
• Optional: expansion puck to charge 4x smart batteries per port
• Optional: Puck for 2-12S dumb battery charging and balancing
• USB interface for monitoring and controlling charge workflow from PC
• Optional: Integrated Raspberry Pi Compute module for Wi-Fi and Ethernet connectivity
• OLED screen for monitoring and outdoor viewing
• User Interface engineered for speed and safety. Plug-in to charge-start in less than 4 seconds
• Zero effort to train customers on battery charging and safety. Customer have two options: Regular charging / Fast Charging
• Mechanical design optimized for robustness and repairability

Sign up here for more details.

BatMon is a module that connects to you batteries to "smartify" them. BatMon reads the cell voltage, current and relays it to autopilot or the onboard computers. We made a quite a bit of improvements in the latest v3 devkit. The most important is the support for 3 different protocols :

• SMBUS(I2C based two wire protocol)
• CAN (CAN based differential two wire protocol) 
• LIN (a robust single wire data communication protocol invented for automotive application)

SMBUS is currently supported in the stock firmware. We have added support for Ardupilot, Pixhawk and Raspberry Pi (ROS) environment. 

The features of Batmon are: 

1. Inbuilt Coulomb counting for accurate power draw (and State-Of-Charge) for the pack
2. Accurate monitoring of individual cell voltage ( precise to 50mV ) 
3. Onboard temperature monitoring + extra optional temperature probes for accurate measurement of battery temperature in harsh weather.
4. Stock firmware connects to Pixhawk, Ardupilot, Raspberry Pi (ROS) 
5. Onboard cell balancing
6. Switchable low-power LED indicators display for convenient display of battery SOC
7. Optional OLED display and warning buzzer
8. Optional safety cutoff FET

The first batch of boards are available for pre-order till Oct 31 here: https://rotoye.com/batmon/

UPDATE

We have some good news. A battery manufacturer Titan Power is working with BatMon kickstarter backers to assemble BatMon into Lithium Ion batteries for free! Backers also get a 5% discount on Titan batteries upto $1000 purchase. Now, you can get a custom shape/size Lithium ion battery without having to assemble BatMon into the pack yourself.

Hi robot enthusiasts, 

We launched a kickstarter campaign to support production of “smartification” module for robot batteries. BatMon is a small module that can be attached to your lithium batteries to convert it into smart batteries.

Here are some of the specs:

• Voltage, current, and temp sensors
• 64 bit unique battery id
• OLED display
• Current battery life display
• Automatic discharging to maintain cycle life
• No discharge cutoff
• Open  source case design 
• Dual LED, optional buzzer
• Cell balancing, with individual voltages
• Only 12 grams
• Compatible with SMBUS, PX4, Ardupilot, and Arduino
• Integrated coulomb counting

BatMon data on QGroundControl: Individual cell voltages of 6S cell during flight

Opensource case design for a 6S Smart Battery

If you are interested in a smart battery for your robots or other projects, PLEASE FUND US at BatMon Kickstarter

Designing electric multicopters for a specific flight time is a complex multidisciplinary optimization problem. This short blog post is some of my thoughts on how to think about this problem. Obviously, there so many different ways of doing this and welcome suggestions and other constructive discussions.

From an energy conversion standpoint, multirotors is a pretty simple systems. Energy is available from the batteries which is routed via ESCs to the motor and the propeller. 

The challenging part is that batteries do not always provide the same efficiency(energy). They are dependent on the power draw (watts,current). For most batteries, the higher the current you draw from the battery, the lower the total-energy available from them. This is mainly due to the internal resistance of the batteries which is pretty low (milliohms or less), but not zero. A typical characteristics of few of the different battery cells are given below. The y-axis shows the energy density (Wh/Kg) of the battery and x-axis shows the power that was drawn from one Kg of battery.

Notice how the increased drain causes the energy capacity to drop sharply for all the cells. 

If we ignore the ESCs power loss characteristics, the other significant power conversion is from the electrical energy received to the motor and the thrust provided by the propeller. One intuitive way to think about this conversion is W/Kg. This is the watts input to the system for every Kg of thrust generated by the propeller. 

If we ignore the motor and consider just the propeller, we can define this as

“Mechanical power (watts) supplied to rotate the propeller / Kg of thrust”.

If we consider the motor, this unit becomes “Electrical power input to the motor (watts) / Kg of thrust”.

Shown below is an “electrical watts/Kg of thrust” of various sizes of propellers tested with different motors. The x-axis shows the “electrical watts/Kg of thrust” and y-axis is the total thrust generated by the propeller. Each color shows a propeller of a particular size.

The three things to note are 

• How the same propeller can have widely varying efficiency with different motors. 
• How a given propeller drops its efficiency for higher thrust
• The higher efficiency of a larger propeller 

Designing an optimal multirotor requires matching the characteristics of the battery to those of the motor and the propeller. Would love to discuss more about this is in a later blog

Over the past couple of months, we have been working on a "smartification kit" to obtain accurate state of charge for Lithium batteries. Currently most systems use voltage based capacity estimation which is inaccurate and make it hard for flyers to

• maximize their flight time
• understand changes to battery capacity over time
• choose from the best pack among the many-in-hand to race with

Batmon helps solve all of the above issues and also automatically discharges the battery to storage voltage after set-time to enhance the life of the pack. 

The board currently works with modified pixhawk, ardupilot and arduino firmware. More details about the kit is available here: https://github.com/rotoye/batmon_reader

We also help assemble custom lithium ion and polymer packs with Batmon integrated for your specialized use case. 

Please PM me if you'd like to know more details. 

Happy new year to all flyers. 

We want to update the progress made on an in-flight battery monitor. Initial revisions of the board were meant to capture accurate cell voltages for the flight batteries. However, lot of feedback was received to push the board towards a minimal Battery Monitoring System. Currently, most diy'ers and professional flyers use large battery packs after monitoring them with an external battery meter. We believe its advantageous to semi-permanently attach the monitor with the batteries as Batmon has cell balancing and minimal weight/power penalty. 

The features of Batmon are: 

1. Inbuilt Coulomb counting for accurate power draw (and hence power remaining) for the cells
2. Accurate monitoring of individual cell voltage ( precise to 50mV or better) 
3. Onboard temperature monitoring + extra optional temperature probes for accurate measurement of battery temperature in harsh weather.
4. 9gm weight 
5. Connects to Pixhawk i2c bus with stock firmware to read total battery voltage, temperature, current. Custom pixhawk firmware enables monitoring cell voltages and many other battery parameters.
6. Low current onboard cell balancing. 
7. Switchable low-power led display for convenient display of battery vitals (~3mA / 40V with display on)

Batmon battery monitor measuring 10s

9gm board

Would love to get feedback. We will build ~100 boards end of March,2019. Please PM me for feedback/pre-orders.

Active current drain: <5mA
Total sleep current: < 20uA
Sleep current drain per cell: <1uA

Interface with autopilot: i2c , UART (will implement other protocols if there is interest)

Pics of first version monitor

Thought you might like a lazy way to get that cold soda at your party.