I think there are, on some cars, phantom drain issues. That, plus they do fit very small and crappy 12v batteries as the cranking amps/big power not needed. I don’t understand why they don’t just fit a lithium battery – well, I do understand, it’ll probably be 50p more expensive!
Kia /Hyundai had problems early 2021 with their charging regime for the 12v, it basically didn’t allow for it to be charged often enough and, when on charge, it was for a short period only, so loads went flat. They updated the software and included a lot more 12v charging sessions which solved the issue (unless you had a component causing 12v drain – see phantom drain above).
I’ve had a Kia Soul since mid 2021 then an Ioniq 5 since Jan 2025. Neither has had any issues with the 12v. But I do spend a fair bit of time in Utility mode – and that defaults to charging the 12v when on, so I may be helping the battery cope with any suboptimal conditions.
No ICCU issues for me so far – 11,500 miles…touch wood…avoid black cats etc…
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