Another BMS recall for the Kona

[Electric Rich]

I heard wind of another BMS recall and sure enough, after checking my Vin# with Hyundai, they want to run some diagnostics on it. 2019 Kona EV
Checking for battery cell damage and updating BMS software I think. Sounds like the current BMS S/W may lead to over heating/charging and cause a fire in super rare cases.

 

[Tim94549]

Where you located? I see nothing for mine - 2020 in US

 

[KiwiME]

I heard wind of another BMS recall...

It applies to all 1st-gen Konas (104,011 worldwide acording to a German source) and the Ioniq 38, but it appears not the Ioniq 28.
The 2nd-gen Kona is not affected.

Like others it's been worded for the worse-case scenario. It's the same procedure as every other BMS update we've had, meaning they may stumble upon a few battery packs that are out of spec and require replacement. The update was issued in parts of Europe from January 2026 and is just now being rolled out in Australasia as you've noted. The reason for the delay could be as simple as Hyundai not wanting to overload their service portal, or that the update needs to be processed by regional vehicle safety regulators.

The basis for the recall as best as I can determine is that Hyundai are reducing the tolerance needed for a dash warning of either abnormal cell-group voltage imbalance or high battery module temperature. It's not clear to me yet that this was strictly a voluntary action on the part of Hyundai, but it is noted that it was not due to any catastrophic events.

 

[JoeS]

Along with care and feeding of the batteries to maximize their longevity, there is a complementary activity that we should perhaps be performing regularly: that of properly exercising the Battery Management System (BMS).

There are at least two BMS functions that we can help: Cell Balance and State of Charge (SoC) calibration.

Can someone provide links to where specifically these two topics are discussed for our Kona? TIA

For example, cell balancing (a very slow process done in small increments) on my i-MiEV only occurs at the top, after the battery shows it's fully charged (16/16 bars) and before it stops charging by itself. IIRC my old 2013 Tesla does slow top balancing above 93%SoC, whereas modern Teslas and my homebrew solar battery BMS have continuous balancing independent of SoC. On my i-MiEV the SoC calibration is done by discharging the battery down to two bars (2/16) and then letting it slowly fully charge undisturbed until it stops charging.

 

[KiwiME]

There's been little discussion of any substance unfortunately. I've mentioned a few times in the past that balancing after charging on the 1st-gen Kona can be witnessed using a BM2 as the BMS runs entirely off the 12V battery when the traction battery is offline.

I've seen this after every home charge where I use a 2kW EVSE exclusively. This was one of the longest durations at 4.5 hours. it appears to be programming the individual cell-group loads every half hour to suit the corrections needed, then sleeping in-between.

I've only been made aware recently that it also likely takes place while charging. There's an interesting article about a Ioniq 28 owner who was focused on getting the best possible range at 100% charge, which requires the highest possible pack voltage be obtained when charging stops. In a nutshell he found that balancing was too slow to keep up while on a 7 kW rate. Slower charge rates generally resulted in higher final pack voltages. This voltage variation (of about 5 volts) had been noted among Kona many years ago but no one even recognised (or cared) that it affects range slightly when you've already got 480+ km.

The concern I have relevant to this thread regarding the BMS update is that with (3) cells hard-wired in parallel per series group it's exceeding difficult to detect a single failing cell. My original (Sept-2018) pack always had one particular cell-group low by the (minimum readable) 0.02 V (which I'll assume means it could be as bad as 0.039 V since 0.04 V is the next increment).

I only recognised later that the fact that one group could never could achieve a closer balance was the unmistakable sign that one cell was continually self-discharging at a very low rate. The 'MIN cell' value was always #54. I monitored that situation periodically for four years and it never got any worse but I really should have asked Hyundai for my replacement battery sooner. The new pack has always had perfect (<0.02) balance.

This new BMS update needs to look for trends like this to spot problems. The 2nd-gen Kona and Niro has only one cell per group which was a smart move to side-step this issue.