There are now at least three apps on Android that enable access to the battery and motor data from the Battery Management System (BMS) via the On-Board Diagnostic port (OBD2). It’s like a customisable version of “LeafSpy” but for other cars. Why would you be interested? If you need to ask then this probably isn’t the post you’re looking for 😉

The Ioniq is blessed with battery cooling and heating. This image from the Hyundai website shows the heaters on each battery module, of which there are ten; there is also a fan that draws air from the cabin through the pack to cool it, exhausted into the right rear wheel arch. So far I have only heard the fan running after repeated rapid charging.


Torque: This app works on any OBD2 car, ICE or EV. This means it’s very flexible but the cost of this is that there’s some setting up to do. If all you’re after is a quick check on temperatures and SOH then I’d go straight to EVNotify. Setting up the app isn’t hard, see the bottom of this post for some details of how I managed it. All you need is the right Bluetooth OBD2 adaptor and an Android phone or tablet.

This video shows an overlay of Torque data with video to show the kind of thing that’s possible (it’s not mine).

Battery temperature is a key piece of information missing from the Ioniq’s dashboard, along with charging speed. There’s also the question of battery thermal management- fans and heater status. I’ll add the information here as I discover it – and as UK weather allows.

EVNotify: This app is the easiest to use, its main purpose is to give the Ioniq driver a notification of state-of-charge remotely. It also has useful data on battery temperature and some logging capability.

canIoniq: Also designed for use with the Ioniq, has a large number of screens charting many variables like temperature, power, voltage and current. Worth a look, I’ve yet to spend much time with it.

A rapid charge as seen by Torque

This chart shows the battery temperature and State of Charge (SOC) while charging at a Polar Ultracharger. I’ve made the chart in Excel.


As the charge starts, the current ramps to 125A and stays there until around 80% SOC. At low SOC this doesn’t correspond to 50kW- because the battery voltage is low, at 15% SOC I was at 332V at rest. When the charge started, the voltage rose to 348V. Multiply this by the 125A (which seems to be the maximum available from a Polar Ultracharger), and a 43kW charge rate results. For reference, the expected range of voltage for the 96 cell pack is from 3V to 4.15V per cell, or 288V to 398V for the pack.

The battery temperature at the start of this charge was 12°C.

At 78% SOC the charge rate peaked at 49kW, at 391V. At this point the current started ramping down and at 81% the charging rate had dropped to 35kW. Temperature peaked at 30°C, a rise of 18°C. The next morning (after a mild night at around 8°C) the temperature had dropped to 13-16°C. There are 8 temperature monitors on the pack and two “heater temperatures”. Pack Temp05 and Temp08 were 3°C higher than the lowest, Temp03. I’m guessing that since the pack had naturally cooled (rather than the fan forcing cooling air over the pack) that 05 and 08 are furthest away from any vents.

During this charge the fan didn’t start, nor would I expect it to have done. I didn’t charge any further on this occasion- since already two Mk2 Leafs had been frightened off using the charger by my presence!

This 66% charge took 20.1kWh from the charger, and assuming 28kWh available, that’s 18.5kWh absorbed, leaving a 1.6kWh loss- or 92% charging efficiency.

7kW charging

I charged from 13% start 100%, 24.4kWh (again assuming 28kWh useable capacity) compared to 26.9kWh recorded by the Polar charger. This corresponds to 90.5% efficiency. Charging for just over 4 hours, so the overhead of running the charger electronics for longer leads to slightly lower efficiency than rapid charging. Temperature increased by 5°C for an 87% charge, so a lot less than for the rapid charge- and with similar overall efficiency this suggests that the losses are probably in the charger/inverter, not through heating in the battery.

How full is Fully Charged?

It seems to be believed that some capacity is”reserved” to extend battery life. Comparing the BMS State of Charge with the Displayed SOC we can see how much. Any reduction in this reserved capacity may be an indication of battery degradation.

At low SOC I’ve seen little difference between the BMS SOC and the Display SOC. Any difference is the “hidden” capacity that’s unused, at least when the car is new. So far we’re guessing as to how Hyundai have set the BMS up, and one guess is that some capacity is “reserved” to hide degradation, and that this reserve will be used to compensate for natural degradation as the years pass. So it might be 2021 before I see anything significant on this car. At 100% charge displayed, the battery is actually at  95% of it’s potential full charge (BMS). So it seems 5% is reserved at the top end. Will this change? Maybe Hyundai will keep a 5% margin no matter what the capacity; after all to use 100% would accelerate one degradation mechanism. At this point, I noticed the cell voltage is 4.12V at rest, so if we assume 4.20V as the true maximum available, then 95% sounds about right. Time will tell whether a 100% displayed “full charge” eats into this margin in years to come.

It seems Hyundai are relying on drivers not completely discharging the battery to provide a buffer at the bottom end – seems reasonable. At 12% displayed, the BMS shows 13% so there is some low-end buffer, but maybe not as much as 5%.

I found this interesting chart by Miguel Ramos at the IoniqForum site which explains many features of the Ioniq BMS. NB I’ve noticed that the precise SOC at which features occur varies with battery temperature, so in reality Hyundai’s BMS is a 3D map, not a line.

  • Regen braking is limited somewhat at above 94%, but only to 60kW which is still a lot. (My 2013 Leaf only ever had 30kW of regen)
  • Maximum power is limited slightly below 14% charge, however at that point I expect most drivers would not be demanding a lot of power. For reference the car only needs 21kW to cruise up a motorway incline at 65mph.

Battery Degradation

On UK Nissan Leaf 24kWh cars, by the 2 year point the average degradation was 9%, (the “State of Health” reported by LeafSpy was 91%). At the same point, this Ioniq is reporting 100% – or zero degradation. That’s progress!

Want to get Torque on your Ioniq?

There is some help on setting up Torque for the Ioniq at the link below- but in my opinion it assumes a lot of prior expertise.

I used a “Panlong” brand OBD2 Bluetooth adaptor and an Android phone (Moto G4). I tried my older non-branded OBD2 (that worked on the Leaf) and it didn’t work. The only tricky part was getting the config files into Torque. This might not be the most direct way, but it worked for me as a user, not a coder!

The files are on “github”, see the link above. To get the files onto my PC desktop I viewed them in “raw” mode, and copy-pasted them from github into notepad. Then saved onto my desktop, making sure the extension was correct. After emailing them to myself (to get them to my phone) I could download them in Gmail to my phone “downloads” folder.

With hindsight, I’m guessing that I could have downloaded the files direct to my phone.

Then you need to download Torque (the £2.95 paid for version, not the Lite one) and a file explorer such as “Astro”. After setting “view hidden files” you’ll see a folder named “.torque”. Inside this folder is the “extended pids” folder where the 4 files need to go to be found by Torque. Move the files there.

After starting Torque you can select items to display, like this:


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