BM2 Monitoring on Additional 12 Volt battery fails

Discussion in 'Hyundai Ioniq 5' started by CharlesBranch, Sep 16, 2022.

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  1. On 7-16-22 I posted about my 12-volt battery failure ( https://tinyurl.com/4ekfrhsj).
    Electriceddy suggested that I get a BM2 monitor and report back. On 8-5-22 I posted my first experience with the BM@ monitor (https://tinyurl.com/3bz62a84).

    I have now had two more issues while using the BM2 monitor. The first image shows the first incident on 9-6-22 in some detail. P1060118_Labelled.jpg I had parked the Ionic 5 with about 12% (25 miles) remaining. Between 8-31-22 and 9-5-22 I noticed numerous small dips indicated by the blue arrows, but they did not appear to trigger the charger. The charger did apparently come on several times and again when I made a couple of trips. On 9-6-22 I decided to go to an EA charger, but the car was dead again. I connected my jump starter again, drove it to the local charger, and charged it to 90%. I checked the BM2 data and saw that the voltage had spiraled down over about 24 hours. P1060117.JPG On 9-6-22 the voltage fell as low as 6.98 volts. P1060116.JPG
    A few days later I again parked the car with about 12% (30 miles). On 9-15-22 I went to the EA charger and again charged it to 90%. When I got home, I checked the BM2 again and realized that another spiral had begun, and I apparently got lucky this time. This image shows the previous failure and then the near miss. P1060121.JPG The voltage fell to about 11.83 and jumped back up when I drove to the charger. P1060120.JPG
    This makes a total of two complete 12-volt failures plus a third near miss, and this does not seem normal to me. It looks to me like the voltage dips briefly about 1/3 volt about every 20 hours or so. The 12-volt charger comes on occasionally and whenever I make trips. But for no obvious reason, it starts spiraling down, but that does not trigger the 12-volt charger to come on. On all three occasions, the death spiral seemed to begin when the big battery gets to about 11 or 12%, but that should be plenty of power to turn on the charger.
    Questions:
    1. Why does the 12-volt battery voltage fall so fast?
    2. What causes the small voltage dips every day or so?
    3. What finally triggers the 12 volt charger to activate?
    4. Why does the voltage go into a death spiral?
    5. Why doesn't the big battery charge the 12-volt battery even when the big battery has plenty of capacity remaining?
    BTW: My FM radio has quit working, and I still notice the burning odor after it has sat for a few days. In spite of all this, the car is a real pleasure to drive. But my wife has started making fun of the car and has even used the "L" word.
     
    Last edited: Sep 16, 2022
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  3. Wow, lots of good info in those attachments.
    Assuming Ionic 5 has the same characteristic charging algorithm as Kona EV, the daily dips are probably due to BMS cell checking. The trigger to activate the 12V charge is determined by software, LDC receives information from a sensor (IBS) providing discharge rate of the sub battery and applies output.
    The discharge spiral may be caused by several documented findings as an open or not latched hatch or door also repeated queries by Bluelink, there have been others as well.
    Thanks for the posted info, perhaps check if any changes to the LDC have been applied in the form of an update at the dealer;)
     
  4. Thanks. I'm pretty sure the problem is not from open doors, etc. It has happened 3 times now, and each time it happened when the main battery was at about 11 to 12%. Surely this is not normal. My 2006 Honda Element frequently sits for months, but still cranks readily. I have also seen several reports of people letting the Ioniq 5 battery run down to zero when doing range tests. At 11% the main battery should easily have enough power to keep the 12-volt battery charged. I'm not sure just what to tell the mechanic when I take it in to get the FM radio fixed and check the charging system and HVAC for the burning smell. If I show him all these graphs, he will probably just think I'm a smart ***. :) I will try turning off the BlueLink to see if that has any effect.
     

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