I’m moving from the 0.1 HW version to 0.2 with big updates. I have decided after tinkering with the 0.1 prototype board, testing it and more importantly looking at other possible IC solutions to make the design have a better feature set, same price and same footprint. Well I found an affordable battery stack monitor IC from Texas Instruments, which supports up to 16S configurations and I can cut my total component count to less than half, fit all components on one side of the pcb (cheaper/faster pcb assembly). Now this does mean that the BMS now needs a microcontroller, but as it doesn’t have any crazy connectivity, it can be a pretty basic one, but this then enables a lot of smart features for it.
So the originally simple and dumb BMS is now becoming smart!
Thread got started with some initial general project ideas, but it has now converged more towards a small form factor dumb BMS, as the market already has decent and affordable dumb BMS’ from Daly for example, so folks threw around the idea to make it a really small form factor to make it distinct from the competition.
early PCB mock-up at 18x65mm size:
So currently the project parameters are:
- Same PCB size as a 18650 cell (18x65mm)
- 3S-12S cell support (11.1V-44.4V)
- 8A-12A charging current
- 5A discharge path control for accessories (undervoltage protection, so they don’t drain the battery empty)
- SPST switch control for discharge control, to turn accesories on/off
- Overcurrent protection
- NTC-temperature probe support for over temperature protection
Are you interested in the project?
- Yes, I’m interested
- No, I’m not interested
I have done some analysis of the cheap chinese BMS’ and have figured out how they are hardware wise implemented, so I’ve been wondering about making my own “dumb” (no programmable logic) BMS design based on the chinese “dumb” ones, but made with actually known components and I’m wondering would there happen to be any interest if I were to sell some as DIY kits with PCB and components included? I’m gonna designing a “dumb” BMS platform for my own use anyway for use in integrating battery packs into projects, so that’s why I’m asking.
The design can be scaled pack S-count wise between 3S-18S (fully or partially populate components), but same PCB. Both charge and discharge path control can be implemented (over-charge and -discharge protection). Adding a thermal probe is possible. Overcurrent protection is also possible. Should be pretty affordable especially if I only need to supply PCBs and can volume buy the needed components for the kits and there is no firmware development needed.
Basically the minimum BMS implementation with no extras, but enough to protect from overcharging, overdischarging, overcurrent, balancing and over temperature (under temperature also implementable).
Chinese “dumb” BMS for reference. We can improve on the connection placement though.
- Yes, I would be interested in a DIY kit
- No, I’m interested in a “smart” BMS
- No, I’ll buy a chinese one instead