Installing an inexpensive 12V battery monitor

Discussion in 'Hyundai Kona Electric' started by KiwiME, Feb 29, 2020.

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  1. I bought this item because I noticed a UK owner had one on the SpeakEV forum. It's a voltage logger for a 12V car battery and is connected permanently across the posts, drawing a mere 1mA. It logs voltage to internal memory every 2 minutes and overwrites old data after 31 days. That data is accessible by the free app (both Android and iOS) when in Bluetooth range and is displayed on a graph in 24 hour segments, which you can screenshot. A cursor is available as well but there is no apparent way to download the data.
    While using the app within range it updates and graphs every second. There are configurable low 'SoC' alerts as well but you have to be in range to get them immediately and so that feature may not be that useful for me, along with a couple of other inapplicable ICE-related options.

    The logger is found on eBay as BM2. Fortunately, the install is an absolute breeze on the Kona EV and does not require loosening the post clamps, although you could do it that way. All I needed additionally were (2) M5 low-profile nyloc nuts and a small lump of Blu-Tack. The existing post clamps have just enough exposed thread to attach the spades on top of the clamps nuts. Using nyloc nuts assure they will not go astray if they happen to loosen. The spades need to be squeezed together carefully to encompass the 5mm stud. Obviously the Blu-Tack is used to secure the logger onto the battery but any other means is just as valid. The leads are solid core wire so you don't want to leave it hanging.
    After installing the app I did not enable location access while not using the app. They say that's so it can connect automatically when you are within range and it's needed for the alerts.

    I'm hoping to use this to characterise the 'aux battery saver' function and other conditions when the OBD port is not available.

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    Last edited: Feb 29, 2020
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  3. Here are some graphs. On the first, actual Kona data starts at the far right, where an AC (7 amp) charge event started at 2100 hours, which I knew would take just under 2 hours to complete, noting the little glitch. The car had been sitting for 5 days unused. You can see that the aux battery was charging for the first 30 minutes. I'm assuming that the ~13 V was 'surface charge' as they say and that when I unlocked the doors the next morning at 1030 that was partly depleted.

    Note that the 'aux battery saver' did not kick in overnight, as I might have expected.

    Several further notes:
    The app connected directly to the logger without having to 'pair' it in the phone settings.
    There doesn't seem to be any way to erase data.
    Disconnecting the unit is the reason for the 9.0V portion from 1530 to 1600 after I benched-tested it.
    Both iOS and Android apps seems to have the same features.
    Data is read on the fly by the app off the logger, it doesn't appear to save anything on the phone or tablet.
    The voltage reading matched my DVM to within about 0.05V.

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    Last edited: Feb 29, 2020
  4. hieronymous

    hieronymous Active Member

    I would suggest rather than your blu-tack, that 2 pairs of velcro buttons, each half firmly glued but peelable, would ensure your BM2 monitor can't shake loose from that position. Also good for tightening up vibrating panels...
     
  5. mikeselectricstuff

    mikeselectricstuff Active Member

  6. mikeselectricstuff

    mikeselectricstuff Active Member

    I don't see any fuse in those terminals - that could be a fire waiting to happen
     
    electriceddy likes this.
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  8. OK, if that's true, then ...
    ... how did you save the logs?
     
  9. sniwallof

    sniwallof Active Member

    Been watching this thread to possibly use a BM2 other cars. I noticed too, no fuse. Presumably (?) there is some fuse type protection in the box, but that will not help if the pinch or crimp is between the box and the pos. battery terminal. Is there a small fuse that can easily go between the pos. term and this lug? Or, maybe better to tie it into the fuse box on an always powered fuse?

    Are people who have used the BM2 satisfied with it? It is the first dedicated 12V logger that I've seen at relatively low cost.
     
  10. As an experienced design engineer I'm well-conscious of safety and I would not have installed this had I been unsure of its quality. The manufacturer has a website with numerous battery care devices that all look very well made, and they also make EV charging equipment. The docs say it's protected and just to confirm that I've sent them an email.
    Noting that the common way voltage is measured is via a resistive dividing bridge, filtered and feeding an analog input to the microcontroller, I suspect that even if there was an internal short and no other protection the PCB trace would just burn up and barely melt the case, rather than create a fireball that might leap around under the hood to whatever might be combustible.
    As a note, this seems to be cheaper on Amazon rather than eBay.

    Also, could we keep please this thread confined to the install and use of this product.

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    navguy12 likes this.
  11. Cheapest I see on Amazon is $32.75 total, or a buck less if shipped from China.

    Just bought one on eBay for $26.79 including CA tax and shipping from NJ. Do you have a link for cheaper on Amazon?
     
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  13. No, just realizing that it was about the same, shipping from China from the eBay vendor I chose was free but it still cost around US$32 and took 6 weeks. Amazon charges a reasonable $6 for shipping, making it slightly more expensive in fact but it probably would have arrived a month earlier had I bothered to shop around. Still, for a few dollars either way it's a useful item to have on hand.
     
  14. mikeselectricstuff

    mikeselectricstuff Active Member

    I used a different logger that downloads to a PC via USB
     
  15. sniwallof

    sniwallof Active Member

    Agree that the something in the box would likely vaporize in a short circuit condition. However, the problem might be the positive wire from the battery terminal to the box. It would probably just vaporize too, but I'm not sure that is good safe practice. Some kind of tiny fuse element at or very near the pos. terminal would be better. Unless the wire gauge is so small in the pos. connection, that the wire opens before the plastic insulation burns? (where the short is to the pos. wire, before any protection in the box)

    BTW, There are a surprisingly large number of design engineers (also, many experienced technicians) on the EV forums, many also with extensive electrical safety experience.

    Let's skip the, if you are worried about it, don't buy one. It is a very clever idea, I am thinking about trying one. Looking around the web, there are many, many listings, so if there is a problem, it has not shown yet.
     
    Last edited: Mar 2, 2020
  16. My studs are M6. Fortunately I tried the M5's before leaving the hardware store; they looked a little small.

    Is this yet another Hyundai localization, or are yours M6 too?
     
  17. Oops, you are correct, M6. Sorry for the confusion ...
     
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  18. Three days of 'aux battery saver' charge events starting the first day the Kona sat unused. About 18 minutes duration each with a 24 hour gap from previous charge stop to next charge start, noting that the time resolution is 2 minutes. Other voltage glitches are due to unlocking the doors and entering Run mode but not driving, which did not seem to disturb the charging schedule. The charge seems to leave the battery at about 13.0 V then the voltage appears to run down at a rate of perhaps 0.12 V a day. My car has no owner-added loads other than this logger device.

    Will be interesting to see what others come up with, particularly if imposing an external drain on the battery causes a correction in the schedule or duration.

    7AE0F8D6-84D2-4F68-A5BC-CAD4252514FB.png About 14:59 to 15:17, 18 min 287C5762-139C-4B1B-83F1-0026C2A9CEA1.png About 15:17 to 15:35, 18 min D73044B0-11F0-4193-88AA-3A05B1C03B32.png About 15:37 to 15:55, 18 min
     
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  19. Although I don't have a scope or app to view the waveforms etc. I can vouch that an external 100W load for a duration of 6 - 8 hours had no significant
    negative results to my 12 V battery. Still floats at about 12.6 V no load measured with my Fluke. I have done this several times and have a cord and inverter ready at all times just in case- runs the fireplace fan for heat. Of course I keep the car in run mode when I do this (DRLs off)
    Sorry if off topic a bit, just trying to add input to your question. Maybe try something similar and see what occurs.
     
  20. Well, under Run or even Utility modes the LDC keeps the 12V system voltage continuously high enough to avoid any discharge from the 12V battery, but you have to tolerate around 200W draw off the traction battery just to keep those electronics alive in addition to your 100W inverter load.
    The question is more when the car is 'off' can the aux battery tolerate user-added 'parasitic' loads or Kona 'sleep' loads that remain higher than normal for whatever reason, such as an open door. And further, does the aux battery saver recognise the additional charging needed and compensate in some way.
     
  21. Has anyone been able to prevent the BM2 app from running in the background on Android? I only want it to run when I start it myself.

    It is on the Settings list of Always Sleeping Apps, but keeps running anyway and keeps a notification showing, including on the lock screen. If I kill it, after a while it pops up again.

    Is there any reason not to turn off notifications? Are any of the alarms useful? The Power Alarm might be if it can measure SOC, but it probably triggers on voltage.
     
  22. Robbert

    Robbert Active Member

    Caught this thread a few days ago and ended up getting one of those monitors as well. Can't ever have enough data, right??
    So.. The car has been sitting in the garage since last night when I drove for >1 hr. Not connected to the AC charger. The 12V battery float is currently around 12.57V. When I installed the battery monitor unit, I turned the car on for a little while, and the voltage shot up to 14.3V (charging). After turning the car off, the battery dropped to 12.15V, and has slowly crept back up to the 12.57V over the last hour. Should I be concerned that the battery is going bad? It's cold outside today (~28F this morning).
     
  23. 12.6 V is a good floating voltage, battery appears to be good SOH
     

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