Valdemar wrote:I posted this in another thread, someone on a foreign Leaf forum claimed he hacked the 2011 BMS, he even posted a screenshot of a hex editor (EEPROM image?) and pointed to locations that keep the AHr and the capacity bars. He said he could store whatever values he wanted at those locations effectively restoring the capacity gauge to 12 bars (temporarily of course). Or he could "pair" a 2011 BMS to a 2011 Leaf without Consult III (not clear if battery disassembly was required). Same person said he couldn't hack the 2013+ BMS, or at least not yet, so even with his knowledge your job wouldn't have been easier.
I have a theory that 2013+ cars have a slightly different BMS than that which comes with new replacement packs intended for installation into 2011/12 cars, for one new Leafs have 3 temperature sensors but 2015 replacement packs in older Leafs still show 4 in LeafSpy. As such, it may never be possible to swap the battery as a unit from a 2013+ Leaf to 2011/12, and moving modules will remain to be the only available option.
Definitely there are differences between 2011/2012 and 2013+ BMS, that is why the later ones have colored connectors (grey on side and one dark blue instead of the 4 white ones at the bottom) Also the ASIC chips appear to be a different version of that chip, even communication with the ASICs is different as seen by the guy that is replacing the BMS processor with a programmable device.
But the differences between the programming for a 2013+ BMS to be compatible with and older car is only software, although having an extra tempsensor in the pack is definitely a different hardware and wiring harness, but if a 3-sensor 2013+ pack gets a software that simply doubles the reading of one sensor to simulate a 4th for the car then there is no need to physically change a 2013+ for an older car, except that the OBD and contactor control connector at the front has a different pinout. I never understood why that was necessary, but oh well.
The discussion about the temp sensors also made me think about the function of the 25th ASIC that I saw on the BMS board and I now suspect that it is used to measure the temp sensors. Although it would also be easy for the control processor to do that task, since it has 100 pins and uses only a handful for the serial communication on CAN and the serial EEPROM and the serial communication with the 24 ASICs in daisy-chain. I am getting the impression that a 16 or 24 pin device would have been sufficient, but who am I.
I agree that swapping new cells into old packs (retaining the 2011/2012 shell that can be opened and bolted shut again) complete with the old contactors, service disconnect, wire loom, sensors, bus bars and BMS - just swapping out the cells themselves (still retained in their end plates, so you have 3 modules: the half-pack of 24 vertical modules and two quarter packs of horizontal modules. All can be moved by 2 strong people, though you may need protective gloves. The weight of the 300+ pound halfpack was enough to almost break skin when carrying it by its brackets with bare hands. It is just a lot of time to undo and re-do almost 300 bolts in a safe way. The only creativity needed is to move mounting brackets for wire loom attachment to the new pack, since it has mounting bolts every 2 modules instead of every 3, and to remove the power connection ends of the old bus bar and attach them to the new bus bar, because the old bus bar interferes with the brackets on the new half pack. Also the temp sensors cannot be inserted at the same module positions, but that is not a big deal.
Total amount of time is more than a full day work. I actually cut myself on a sharp bracket when my wrench slipped from a very tight nut, so I had to stop a few days halfway re-assembling the new pack, because I needed 2-hand dexterity to allow safe working on this. Also I was doing a 3-way swap and this cost me at least 2 full days, spread over almost a week, after the initial attempt to simply bolt the new pack into my neighbors Leaf and finding the reduced power due to the pairing issue, I had to:
- remove their old modules from my old neighbor's pack
- install the new Lizard modules
- re-install all bus bars (I had taken the 24-module bus bar completely apart to adapt to the new modules)
- then put all original 2011 wiring, contactors, disconnect and wiring loom back in the 2011 shell with the new modules
- retrieve their original BMS from my secure storage and plug it in after a quick prayer
and then bolt it back into their car,
turn the car on and confirm *no more error lights*!
Then secure everything, add belly pans and button everything up and take it onto the street to confirm full power and no speed limiter.
*Then* I had to put the gutted 2015 shell away (anybody interested? I still have it, together with 2015 belly pans that fit this pack)
and retrieve the "Washington State" pack from my own Leaf, open it and remove everything except the modules.
Then the creativity started: how to put the 2015 contactors (with different plug wiring and current sensor delete) and disconnect (with new current sensor attached) together with the new wiring loom and bus bar wiring all in the 2011 shell with different mounting positions?
That was the slowest part of the job, but I found solutions for all issues, sometimes hacking off or bending away extra mounting references, or banging a leg to bend it enough that an almost-fitting mounting hole could be used, sometimes inventing new fastening. And a couple things I simply re-used the original 2011 part such as the mid-pack reinforcement bar.
So yeah, this is not something that a business would easily do but a shade-tree person like myself can spend their own time on it and get their own car to run normal with a new pack.
I still have the reduced-to-75% original pack from my neighbors, together with another pack that I picked up from Sac City auto dismantler
and those two will go into my EV truck to give that a range comparable to a 2016 Leaf's 30kWh pack... So many projects, so little time. Good that I can re-use the Leaf BMS'es on those two packs, I will need to write some SW for the CANary project to read the two CAN buses from the two BMS'es and present the two packs as well as alert on overcharge (turning charger off) and under-dis-charge to alert the driver to stop driving or even override the accelerator to draw ever less power from the pack and in case of emergency, drop contactors.