LEAFStat August 13, 2014 Mark D Larsen

OBD-II ELM327 WiFi (click to enlarge)

Readers are undoubtedly aware that, given the sophisticated electronics in newer vehicles, service technicians at dealerships nowadays use specialized equipment and software to extract data about a vehicle’s functions and performance from its CAN bus (“Controller Area Network”). It was inevitable that curious owners would also want access to those data, and —sure enough—programmers are now developing such utilities for use with cell phones and tablets. The Leaf Spy app appeared last fall, and is now also available in Lite and Pro versions. Unfortunately, the program only works on Android devices. Consequently, for many months I have been waiting and hoping for an iPhone version —in vain.

I was therefore happy to learn that, a few weeks ago, Broad Reach Software released a similar app for iPhone, LEAFStat. I immediately purchased, downloaded, and installed the program on my phone. Then, to interface with the utility, I shopped around for a reliable code reader for my Leaf’s OBD-II port (“On Board Diagnostics”). Eventually I ordered a Super Mini ELM327 that transmits data via WiFi, shown at the top of the page.

I am particularly pleased with two features of this model. First, unlike cheaper units, it has a power button so that you can leave it permanently plugged in and simply turn it on and off when desired. Second, it truly is a "mini" unit that sits horizontally in the OBD-II port. You can see it mounted in my Leaf in the photo below on the left, taken with the camera looking up vertically from the floor toward the underside of the dashboard. On the right you can thus appreciate how small and unobtrusive it’s ³/₄" size really is. Most code readers would be sticking down 3 inches into the footwell area.

Ready to Roll (click to enlarge)

Low Down (click to enlarge)

The Mini ELM327’s blue power button is slightly raised, so you can easily reach down, feel its small bump, and turn it on and off as desired. Another nice feature is that its lights shine and pulse through the “top” (front side) of its plastic cover, and thus you can see when it is, in fact, operational by simply glancing down toward the floor.

Setting up the interface between the ELM327 and iPhone for the first time is surprisingly easy. You plug the device into the OBD-II port and make sure its power button is on. You then open your iPhone’s settings, choose the one for wireless networks, and select WiFi_OBDII, as I have done in the screen dump below on the left. There is no need to configure the IP addresses, because the ELM327 automatically enters them, as illustrated in the middle screen dump below.

WiFi'delity (click to enlarge)

Auto Configured Auto (click to enlarge)

LEAFStat’s Stats (click to enlarge)

Compared to Leaf Spy’s multiple features, LEAFStat’s functionality seems basic, bare-bones, even rudimentary. It only displays a single page of information, as shown in the screen dump above on the right. Still, I purport that these are the most crucial data to monitor a Leaf’s battery —and certainly enough for my purposes. Besides, it would not surprise me if future upgrades offer additional features —similar to what occured with Leaf Spy.

Regardless of its current limitations, I am pleased that, in the above LEAFStat screen dump, the capacity percentage and kWh from a 100% charge substantiate one another. Specifically, if an 83.54% capacity holds 17.51 kWh, then 100% capacity should contain 20.96 kWh, i.e., the 21 “useable” kWh supposedly in a brand new Leaf battery! This tells me that the LEAFStat capacity percentages are indeed reliable.

I have noticed a few odd quirks, however. For example, the ELM327 will turn on, light up, and even attempt to transmit data if the Leaf is off, but LEAFStat will only work if the car is fully on and ready to drive —and not just in its “accessory” modes. The tire pressure readouts only appear after driving a sufficient distance to calculate an average for each wheel, but I suspect that this is the case for any OBD-II app. I have also noticed that, if I turn both the Leaf and the ELM327 off, and then plug my EVSE into the car, the unit sometimes turns back on again. My guess is that the automated routine of checking the vehicle’s charging timer probably sends an electrical signal through the car’s internal circuits, and the pulse triggers the ELM327’s power button...? I therefore try to remember to first plug in my Leaf and then turn the device off.

I also have to admit that the other data in LEAFStat confuse me —and do not calculate within expected parameters. For example, since I had fully charged to take the above reading, why does the SOC only show 91.65% —and not 100%? Likewise, according to my understanding, each GID is supposed to represent 80 watts of charge. Yet 226 GIDs x 80 = 18.08 kWh —not 17.51 kWh. I also have heard that a brand new battery should contain 281 GIDs. Yet 226 / 281 = 80.43% —not 83.54%. Something is not adding up correctly with those GIDs.

Finally, I have yet to hear a solid explanation for how HX is calculated, and thus am at a loss to understand what its 69.73% is telling me about my Leaf. The LEAFStat webpage states that it is supposed to “represent a measure of internal battery resistance that develops over time, indicating how healthy the battery is.” If so, how few milli Ohms of resistance are in a 100% HX? And how many more milli Ohms would have to accumulate to constitute 0% HX? Your guess is as good as mine —but I intend to keep looking for the answers.

Now that I finally have a dedicated diagnostic tool for such measurements, I intend to take readings regularly and report the results as the miles continue to accumulate. For those who wonder if their Leaf’s capacity might qualify for repair or replacement under Nissan’s 60 month/60,000 mile warranty, such a tool could prove invaluable.