Not that im disagreeing at all with your theory, but I've every confidence in the design of the voltage monitoring. I can even ID the physical locations of each module based on the info Consult gives.RegGuheert wrote:Thanks, again! That's good information!KtG wrote:The Battery controller has more varied data about voltage than it has about temperature. One can see the voltage of each module individually with Consult. This is good. We techs use this info not just for diagnosis, but for balancing a new module prior to installation. The voltage is displayed in mV.
There are 4 (if i remember right) temp probes. 2 on the rear bank, one for each side bank of modules. I'm pretty sure the battery controller can display them individually on Consult, though I've never looked.
I felt more temp sensors were needed the first time I saw the battery. But im a tech, not an engineer. I wish engineers asked for my input.
Yes, I've noticed from reading the service manual that the cell voltages are displayed in millivolts. That much resolution implies and accurate measurement was made.
Hopefully Nissan made the system truly accurate rather than just deciding that high resolution would be sufficient to keep the pack balanced, which it certainly is.
The ability to control voltage in/out of each is limited though. Resolution there is by stack only, as each stack has its own bus ribbon that connects to the main relays. Short of putting a micro controller in each module (hello costs!), there isnt much of a way to get past that.
Still, with limited temp sensing its all a moot point. Even if the BMS saw a temp spike in one module and a corresponding voltage change, there isnt much it can do beside set a DTC.
I'd say its obvious they (the engineers, but more likely a bean counter) made a boo boo. But sometimes one makes a SWAG, because you can only add so many sensors before you muddy the data. I'd love AFR sensors on every cylinder of my gas engines (and aftermarket systems exist for that), but the cost vs gain is nutty. Same thing for having Intake air temp data in the port right by the valve rather than 3' up the air stream. Only development motors get that level of sensing, and only then when absolutely needed.
I'd like to think that Nissan had temp probes all over this battery in testing, and in production placed the 4 where they give the most accurate picture painted by the 100 sensors. Thats how I would have done it. but again, not an engineer. I'll try to make time to get the Consult on our Leaf Shuttle and see what I can see for individual temps. I'm willing to bet the rear stack is hottest, and is where the problem lies.