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.
"I2C on their resume"... I think you misspelled "CAN" :-D
I2C sounds like mechanism envy, because everyone who programs a computer these days needs to have I2C on their resume. Most of the smart batteries use a single wire interface.
Right. I was relating a little history of why we got rid of the smart part of the only smart batteries that existed when this technology was new. Also, why you wouldn't want to use an off-the-shelf cordless tool pack, which do cut off and, at least in the Milwaukee case, won't turn on again until they're put back on the charger.
We used to make our battery packs out of Milwaukee V28 batteries by disassembling them, discarding the "smarts", and saving just the 7 individual cells to wire into 3s to 7s packs. The reason for discarding the electronics was fear that they would turn off the current if the draw was too much, thus causing a crash. This was in the days that you pretty much had to build your own chargers, so we added balancing connectors to the new packs and to the "smarts" and stuffed the electronics back into the the V28 housing in order to use a V28 charger to get a balanced charge.
Additionally, all that is needed for a standardized battery; with an SMBus output over I2C/CAN/RS422 or whatever...
@kelly, I was referring the electronics as being a no brainer. Indeed getting them to make a battery specifically for drones and then standardize it is a challenge. Chinese battery makers/sellers (aka HK) are reluctant to upset the status quo; failed/over charged/damaged battery means another sale...my M18 was made in China and I've had it for four years; still works.
Flask\hlights originally used standard batteries; A,AA, C,D, etc. Why cann't there be a standard smart drone battery? Probablythe same reason power-tool manufacturers keep insisting on creating their own custom battery designs...$$$..battery investment keeps the customer on a particular tool brand!
All that is needed is a robust socket/connector to take the battery. . The M18, as an example, already has a smart circuit in it.
@Thomas Butler Do you know which (if any) of these batteries are SMBus compatible? I've thought the same thing for a while, that there's a ready supply of smart batteries available for power tools that would be great in a drone. I hardly think of the process of getting a company making them to adapt them for drones as a "no brainer" though.
No need to re-invent the wheel. "Smart" LiPO batteries already exist. They are used by Milwaukee, DeWalt, Black and Decker, etc. I have recharged my M18 Milweaukee drill LiPO battery dozens of times, and it is STILL going strong. The batteries have a robust high-current connector, LED status indicators, etc. What is needed is for one of the companies making these intelligent :"power tool" batteries to make a standardized version for drones...they already have the proven track record of viable battery control logic; just add an I2C/SMB interface for the drone controller! No brainer!
@Peter it is simple enough to use a CAN bus interface which is virtually immune to noise rather than I2C. In addition, the I2C could be optically coupled. "Noise" is really a non-issue here. SMB bus for "smart" batteries already implements I2C, and there doesn't seem to be any issues with "noise"...
You can PM me for ordering a battery.