Quote:
Originally Posted by Cyruscosmo
Hey all
Anyone have a line on an open source BMS? I have 90 60ah LiFePo that I will be trying out in this my first conversion. I would like to build them myself so at least I can fix them myself later.
Also how about a step up converter? I know these units use 650 volts and I am a little fuzzy on whether or not you guys are shooting for that voltage or what is the plan?
Is there an open source step up converter?
Cyruscosmo
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I totally agree with the "fix it myself" philosophy on this. It's one of my main motivators (that and improving the performance) to doing this.
I think the openrevolt wiki has some projects, including a BMS and a charger. I don't know their state of developement.
When I was in grad school, I built a BMS/Charger as my final project. I used Maxim IC's for the data collection; each board gathered data for 4 cells. The system used an 18 series PIC for the central management. For a charger, the BMS controlled a boost converter. The main problem with the system is the communication isolation would draw current (extremely small, but continuous) and discharge the batteries over a long period of time.
I've since found a really nice IC made by Linear Technology. The IC gathers data from 12 cells, and has a great way of isolating the communication. I purchased a demo board along with some IC's for a base of a rev2 of my BMS. The demo board connects to a USB port on a standard PC. When talking with one of their engineers, he mentioned that someone doing a EV project just bought a bunch of demo boards for his project.
At the time, I though "that's an expensive solution." But really it's not, when considering all the design time, etc. The main advantage is that you design the system, control software, etc. In addition, you get full documentation with the demo boards, so fixing something in the future is possible.
The main thing I'd like to do is make some boards that would directly bolt to the Nissan Leaf cells I'm using, so I can get rid of a bunch of wires. Maybe I can just re-arrange their demo circuit. . . Hmmm....
E*clipse