Hi David, The BMS itself appears to be active or at least it can be read by simply powering up the BMS board and connecting Leaf Spy through the CAN bus, so that tells me that it does not *need* the Leaf's other computers to be working, even though it may need some additional logic to allow control of the charger and/or warn the driver when one of the cells goes undervoltage. Or reduce the throttle action to stay within safe cell limits.
There are two ways that I see other hackers approach this BMS: Either via CAN bus talk to the processor on the BMS board, similar to the Leaf Spy, so that is a relatively well documented route, but requires a CAN interface. The other route is to disable the onboard processor and hook up directly to the UART lines that go through the daisy-chain of BMS monitor and balance ASICs that are on the BMS board - this is a series of 24 ASICs each with its own address and normally they are all addressed by the processor but you can log the communication, reverse-engineer it (since the ASIC is proprietary) and then simulate it from a new controller that controls the BMS, charger and operator interface. The last approach is the most invasive but also allows you to easily tailor the number of cells that the BMS is watching by simply wiring and programming around ASICs that are unused. I was very surprised to see that the Leaf BMS is balancing with only 10mA current, while it has 64 Ah (two 32Ah buddy pair cells) pack. That is also why it appears the BMS is active and balancing *always*, even when the car is "off". My own experiments and measurements on Lithium cells show that indeed the self-discharge it small. It can vary by a factor 2 between two cells, so eventually you need something or someone to correct the balance in a pack if you do not want to start ruining cells a couple months after installation, but if the balancing is done continuously then only a few milliAmps can counter the effect of the variation in self-discharge. In my measurements of charging several 180Ah blue CALB cells to approx 10% showed that it took almost half a year in a room temp garage for the cells to self-discharge to the cutoff value of 2.5V for the lowest cell, so that means approx 18Ah in approx 180 days for the worst cell is 0.1Ah per day so that means about 4 mA self-discharge current. Another (the best of the set) was about halfway the discharge by that time, so its self-discharge was only about 2 mA. Over time I saw the cells drift further and further apart from their original start (all identical start voltage, they were charged in parallel and then sat a couple days with just the paralleling wiring attached). So, yes it appears that a Leaf BMS is usable outside the Leaf. I still need to confirm that it is actually balancing while just powered up, there is still so much to dive into after first digging into this US Electricar S10 again. Cor van de Water Chief Scientist Proxim Wireless office +1 408 383 7626 Skype: cor_van_de_water XoIP +31 87 784 1130 private: cvandewater.info http://www.proxim.com This email message (including any attachments) contains confidential and proprietary information of Proxim Wireless Corporation. If you received this message in error, please delete it and notify the sender. Any unauthorized use, disclosure, distribution, or copying of any part of this message is prohibited. -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of EVDL Administrator via EV Sent: Monday, May 23, 2016 12:47 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Where to buy Leaf modules? Other sources of Lithiumcells? On 23 May 2016 at 11:15, Cor van de Water via EV wrote: > I would like to use the Leaf BMS ... It still works even when it's not connected to an authentic Leaf computer? That's a pleasant surprise. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
