My Kona seemed happy on the outside with its new Endurant "starting" battery because it works just fine, but I can see from the BM2 data that it's over-working itself.
I've put the old "Rocket" back in until I can resolve this. I can only deduce that the lower post-charge voltage is causing the car to think it needs further 20-min charge events, which at seemingly random times it issues
en-masse. The new battery (an "Endurant Start Master") seems to have a different characteristic curve when fully charged; it's not a matter of capacity. Whenever the Rocket became discharged, under 12.5 V the response was much the same.
Perhaps I'm not able to get the car to "re-calibrate" itself despite following what I think is the correct procedure, cycle ignition then leave car alone for 4+ hours. Without having a BM2 I'd never know what was happening. The downside of ignoring it is increased wear of the contactors and drain on the traction battery.
I've enquired with Century Yuasa here in NZ who's website recommends the pricey LN1-MF "hybrid auxiliary" model which is not currently in stock. They also suggest an DIN44 AGM as a possible substitute. I'd find it hard to believe that the old Rocket is an AGM because it's not marked as such, but who knows?
This was the verbatim response from Yuasa:
Thank you for your details response.
The LN1 MF batteries are designed for cyclic use more so than cracking. The one that you have replaced it with is the opposite – designed for cracking and not for cyclic use. This will certainly affect its performance in your application and so it is not surprising that it is charging in an irregular manner.
Due to the price difference (and lack of accessibility of the LN1 MF batteries of recent), it is fairly common for the people to replace the correct batteries with a starting/cracking battery. As you have already noted, the vehicles operate fine with them. However, the trade off is that they have a reduced life compared with the correct one.
The LN1 MF batteries are due to arrive in the country mid to late this month. Alternatively, some manufacturers have been recommending the DIN44LH AGM as a suitable replacement given that the AGM is designed for cyclic applications also.
I think the response was mostly generic advice and that the issue I'm seeing is more a vehicle calibration than capacity issue based on the fact that most other Kona owners such as
@hieronymous see similar post-charge voltages the Endurant is providing, yet don't seem to have a problem. I can't see any reason why the Kona can't use a starting battery if lifetime is ignored, it just has to understand that this is the case. If the Rocket is
not an AGM the lifetime has certainly not been a problem.
My options are to pay for access to the service website to see if there is a better calibration procedure, ask the dealer for a recommended battery, or just buy an AGM (perhaps the LN1 MF when available) and cross fingers that it works better.
EDIT: just noted that Hyundai Global Service won't allow access from NZ.