Open source hardware universal balancing charger.
This project aims to create open source hardware platform for the ever popular cheali-charger software.
It is inspired by the fact that I managed to get one of those clone Imax B6 chargers and it was unfortunately one with the unmarked CPU and so uncompatible with the alternative cheali-charger firmware. Well the original firmware this was not sadisfactory for me also. In fact I was looking for it to cycle some NiMh packs for me, but it failed miserably to do so, I was lucky it did not burn down my house.
But the enclosure of the charger is so fine extruded aluminium, and a good design, so I did not have the heart to just throw it out , but also did not stand the useless brick laying around. Probaly it would be possible to reverse engineer it and get running somehow, but closer inspection showed that the hardware probably is not so perfect to bother messing with it, plus the results would be quite unrepeatable, becuse when ordering the charger from the ebay.com it is quite random what version you get. Much better to make one own hardware! The enclousres for those chargers seem to be quite indentical though. So it would be nice possibility for many people to be able to swap out the internals of the charger with the good fully customizeable open source hardware and software. Currently unknown where those enclosures come from and weather it is possible to order custom variants, but for the price (about 15USD) it seems completely viable to just buy whole charger for the project, throw out the original guts, and reuse the case.
For designing the circuit and board my choice of tool is very good free and open source electronics design suite KiCad (currenty ver5.0).
I found some circuits from around the web that is originally known to be compatible with cheali-charger.
The most basic seems to be this:RC-Power_BC6_Charger.pdf
Another almost same example:rc-power_bc6_imax_b6_hobbyking_eco06_digital_charger_voltcraft_b6_digital_balanced_charger.pdf
The one I had in my hands in most parts represented the following circuit, good ideas from there, also this is notably good source for component choice because uses most readily available and affordable components:ImaxB6_clone.pdf
Base design features:
- 6 cells balancer
- 26V max battery voltage
- charge rate up to 6A, power limited to 50W
- discharge rate 2A power limited to 20W
- supply voltage 11-24V (60W)
- Input reverse polarity protection
- Output reverse polarity protection
- Optional external temperature sensor
- UART connection for logging with PC
- Input undervoltage lockout (software)
- Firmware flashing connector compatible with Arduino and USBASP connectors
Improved version from 2.0. Assembled and tested. Now meets the original design specifications! (Exept for the maximum output current:(
Schematic in pdf:TBAMAX2.4.pdf
Kicad project files:TBAMaxVer2.4.zip
Firmware files that I flashed(and avrdude settings):TBAMAX_FW.zip
KiCad project files:EL19Charger.zip
3D rendering of the board with display: