Awesome to see something like this out there. A BMS can get very advanced, and it would be very interesting to see a complex open-source system down the road.
I'm not sure I understand the balancing code. It looks to me like the gate is turned on for any cell over 3.509 V (the conditionals all depend on constants). Doesn't this unnecessarily drain your cells?
thats correct. I'm typing this on my phone bare with my short response.
From 20 to 80% state of charge. The cell voltage will be around 3.3v. When the battery gets charged to more than 3.5v, it is pretty much full. The bms will cut the charger off when the first cell reach 3.6v. Most cells will still be around 3.5. So the ones that are above 3.5 will get drain down to 3.5v and in turn balances there battery pack.
balancing battery is tricky, and this is just one simple algorithm I find to work fairly well.
A Battery Management System contains all the onboard controls necessary for a battery to manage its components. Depending on the complexity of the battery, this includes when to (dis)charge, temperature control, cell balancing, high voltage connections, safety monitoring, and more. A good BMS is crucial in using a battery efficiently and maintaining a long life.
An open-source BMS could play a huge role in the advancement of battery technology. If only automakers would do the same. :)
Excuse my EEE ignorance, but can this be scaled down to say a small robot (think Roomba size), or even smaller to a Li-on battery backup for something like a Beagleboard/Pandaboard?
This is indeed awesome. I was literally just thinking about the importance and potential of something like this. FLUX Power bms are too expensive but remarkable technology. Thanks for doing this. It is open technology like this that will change the market for electric cars.
[+] [-] jroll|14 years ago|reply
I'm not sure I understand the balancing code. It looks to me like the gate is turned on for any cell over 3.509 V (the conditionals all depend on constants). Doesn't this unnecessarily drain your cells?
[+] [-] ricksta|14 years ago|reply
From 20 to 80% state of charge. The cell voltage will be around 3.3v. When the battery gets charged to more than 3.5v, it is pretty much full. The bms will cut the charger off when the first cell reach 3.6v. Most cells will still be around 3.5. So the ones that are above 3.5 will get drain down to 3.5v and in turn balances there battery pack.
balancing battery is tricky, and this is just one simple algorithm I find to work fairly well.
[+] [-] rrrhys|14 years ago|reply
[+] [-] jroll|14 years ago|reply
An open-source BMS could play a huge role in the advancement of battery technology. If only automakers would do the same. :)
[+] [-] lsllc|14 years ago|reply
Thanks for open sourcing this!
[+] [-] ithought|14 years ago|reply
[+] [-] felixfurtak|14 years ago|reply
[+] [-] bombless|14 years ago|reply