Monitor Ioniq 5 12-volt Battery with BM2 battery monitor

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

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  1. On July 16 I posted a new thread on problems I had when the 12 volt battery died.
    Electriceddy suggested that I install a BM2 battery monitor and report back.
    My BM2 has been monitoring the battery for a couple of weeks now. The image below shows the voltage over a 15 day period. The voltage goes up to about 14.7 volts and then gradually decays down to about 12.7 volts. The three periods indicated by the horizontal white lines represent three days when I made the same 3 short trips during the day.

    It looks like each time I take a trip, the battery charges at a voltage of about 14.7 volts. I think some, but not all, of the other spikes also represent trips. I'm not sure what the small negative spikes are. I have not taken any long trips, so I don't know whether the voltage would have stayed at about 14 volts or would have dropped back down.

    So far I have not seen a repetition of the battery going dead like it did in my original post.

    I'm still happy with the car in spite of the strange battery problem and the burning odor I still experience when I start it in the morning after it has sat for a few days.
    Domenick and electriceddy like this.
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  3. The 12V sag is the BMS reading the cell open circuit voltages. Thanks for the above info, it might provide more details if the time range is set for 24 hour intervals. It would be easier to distinguish drive spikes from those automatic programed charge spikes( on Kona EV it recharges for about 20 minutes after a short drive, reoccur about 2 hours later- using newer LVDC software version: then settles into a 4 hour cycle similar to the original version) , they also may occur when recharging the HV battery as well. It has been found that if the HV pack is less than 40% SOC, no charging of the 12V battery occurs as well. I can't vision too much difference in the charging pattern between Ionic 5 and Kona EV, except if the software version is changed. Both models should be using the method described in this Hyundai patent;)
    I might add there have been numerous 12V battery failures associated with Bluelink services where the car will not go to sleep and thus interferes with the auto recharge cycle. I have not enabled this on my newer model for this very reason.
    Also suggest PM @Domenick and see if you can add 12V between Ionic5 and battery in the thread title to avoid confusion with the HV pack (if it is too late to change it yourself)
    Last edited: Aug 5, 2022
    Domenick likes this.
  4. Attached is the 24-hour chart for today. The three 14-volt spikes correspond to the same three trips as on previous days. The first and last were about 30 miles, and the middle one was about 5 miles. P1060094.JPG

    So far as I can tell there were no additional charging cycles other than the three trips. I'll keep watching for the next day or two, when I have no trips scheduled.
    BTW: I could not figure out either how to edit the title to add the 12-volt reference, and also could not figure out how to PM Domenick to ask him to edit it.

    The Ioniq 5 12 volt battery charging sure seems a lot more complicated than the generator system in my old 1957 Plymouth. On that car, the generator once failed in the middle of the night during a long trip, and I was able to slide a long screwdriver behind the brushes, fashion a spring out of the elastic from my underwear, and finish the trip without incident. Fat chance of jury-rigging a solution like that on this car.
  5. I have now run the BM2 for longer periods.
    The first image shows a seven-day period in which I made the same three short trips on day 1 and then left it parked for the next six days. _P1060111_Labeled.jpg The charger came on for the three short trips and came on several times during the next six days with no trips. The 12-volt charger appears to activate when the battery decays below about 12.7 volts, but does not come on during brief negative spikes even below that value. I think the fairly big negative spike indicated by the arrow on August 10 was when I noticed that I had disabled Bluetooth on my phone and had to reconnect. I noticed that spike as soon as I reconnected. I don't know what caused the other negative spikes over the seven days. Also attached is a one-day image of August 10 showing that spike in closer detail. _P1060108Labeled.jpg That spike did not trigger the charger to come on, but it did come on at 18:50 hours and stayed on for about thirty minutes. Presumably, the gradual decay in voltage is caused by some constant power drain even when the car is shut off. I don't think that explains the problem I had with a dead 12-volt battery in my previous post, because it had been sitting only a day or two that time. The voltage certainly decays at a much faster rate than I am used to with my older cars. I sometimes leave my Honda Element sitting for a month or two, and the battery is able to crank the engine with no difficulty. I suppose that the Bluetooth itself could be responsible for some of the decay. I may turn it off if I can and monitor the voltage again.
    Anyway, the algorithm of the charging system appears to be to turn on the charging when the voltage decays below a certain rate, but not if it just spikes below that voltage. As to the causes of the negative spikes, that's a mystery to me.
    electriceddy likes this.
  6. Thanks for posting. I believe (as posted above) lower spikes occur when it activates the BMS to check the cells for any deviations at regular intervals. At least those are on a regular basis. What I don't see, is any regularity in the 12V top up as we have in our Kona EVs. I suspect an update eventually will be applied to Ionic 5 to address that issue.
    I suspect you are correct in the larger downward spike being Bluetooth, which is similar to when Bluelink activates (which is why I opted out to enable) as this has been a factor to several dead 12V batteries posted in the Kona forum.
    I am curious as to what will happen when the OTA updates are enabled in N.A. (maybe just in Europe for now to see what happens- Hyundai to monitor). The last thing one would want is an OTA update at the end of a non 12V charging period. Remains to be seen I guess;)
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