Sunday, January 13, 2013

The BMS is in the building.

I received my Lithiumate Lite BMS kit today from Elithion. It's smaller than I expected, which is a good thing, and it seems very well thought out and built. I put a lot of research into choosing a BMS, and eventually chose a digital one because of the increased flexibility and possibility of integrating with the computer I already have in the car. With 85 cells, the digital BMS was comparable in cost to an analog system of the same size, so it was really a no brainer.
The BMS master unit connected to AC power and my laptop
Here you can see the the main unit that all the BMS daughter boards connect to using cat5 cable. It has a number of handy features for integrating into a vehicle such as 12V outpus for interfacing with the motor controller and charger. It can drive 5V gauges for battery current, voltage, and state of charge with any scale you want. It can even produce a pulsed output for a factory dashboard fuel gauge. Aside from those features the highlight of this system has to be the software.

In addition to collecting data from every single cell once per second and graphing it, the software allows configuration of soft and hard battery limits such as when to turn on warning lights or disable the pack. It also provides graphical gauges for current, voltage, and state of charge. Although the provided application only works on Windows, documentation of the communication protocol is provided which makes me very happy. I plan on using this to allow integration with the touchscreen interface in the car as well as allowing access to the data from my smartphone. More to come once I start taking apart the charger.

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