SkyRC MC3000, weird IR measurement behavior with firmware 1.18

As per above. In my continuing usage and tests, I’ve seen two types of strange behavior:

  1. Sometimes internal resistance (IR) gets measured (and can be seen on the charger display and the Android app), and sometimes not (ie, it shows as “N/A”) ; this led me to start manually commanding an IR measurement every time right after inserting the batteries and before starting whatever operation (charge, discharge,refresh, etc)I was about to do with them, by pressing both arrow keys simultaneously on the panel. Which right now lead me to #2 below.

  2. Even after manually commanding an IR measurement and having it displayed for all 3 batteries in the charger, right now it happened that, after starting the operation I was interested for (in this case, a discharge of all 3 batteries down to 2.5V in order to measure their remaining capacity), 2 of these batteries (in slots #2 and #3) changed their IR measurement to “N/A” (the remaining battery, the one in slot #1, kept showing its initial IR measurement).

All batteries are 18650 Li-Ions, the one in slot #1 was a Wurkkos 3000mAh that came with my FC13, and the other two (in slots #2 and #3) are LG MJ1s bought from Illumn, and all 3 have been performing perfectly so far (so I don’t think the reason for that behavior is due to any issues with any of them).

One thing that could explain what I’ve seen is that I first started the discharge on the MJ1 batteries (on slots #2 and #3) and only about 3 mins afterwards (as it has different parameters) I did the same on battery #1. Perhaps when I statrted the discharge on #1, it messed up the IR measurement for the other two?

Anyway that behavior makes no sense and seems like a bug. Would like to know if anyone else here ever saw anything similar.

TIA!

More data: just repeated the above with the exact same batteries and in the same slots, but now with a charge operation and first starting the battery in slot #1 and then the batteries in slots #2 and #3, but despite changing the order, the exact same behavior repeated: slots #2 and #3 changed their IR measurements from the values that were initially measured to “N/A”, while slot #1 kept showing it.

So, that weird behavior seems to be related to the slot: #1 keeps its initial value while #2 and #3 lose theirs, no matter the order their operations get started.

Hmmmm, I haven’t noticed this behavior. But honestly I have not checked the IR other than using the manual method that you mention. That always works. I will have to try to pay more attention. I normally, only check IR when I initially get cells then after I notice other changes in the cells (mostly capacity). BTW, I know the app displays the IR all of the time. You mention checking it on the charger display. How do you do that? (other than the UP/Down buttons)

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It can be checked anytime by pressing the SNB (slot number button) for the battery in question, then scrolling to the “IR” field (it’s a little ways down).

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For the record, yesterday I got yet another issue with my MC3000: it stopped responding to Bluetooth, and only started responding again after removing power (disconnecting its AC adapter from the wall – I’ve read the DC plug behind the charger itself should never be plugged or unplugged while the AC adapter is powered, to avoid the possibility of electric arcs forming inside the charger).

Also, just unplugging the adapter from the wall, waiting for the charger to blink out and then immediately plugging it back didn’t work: had to count to 10 slowly before replugging, I guess to give it enough time for internal capacitors to bleed out and the affected electronics to become truly unpowered.

I have had Bluetooth fail to respond several time over the last year or so. I always just power cycled it.
But being ignorant, I just have pulled the connector out of the MC3000 and plugged it back in. Timing doesn’t seem to be critical.
And yes, I see it arcing when I do that. I guess I have just been lucky by not breaking something.

BTW, thanks for the tip on the IIR. I don’t think that I have used the SNB for anything more than a handful of times over the 10+ years that I have been using the MC3000.

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Thanks for chiming in and confirming it happens to you too. I was kinda afraid I got a bad unit, and now that you’ve confirmed it and thinking a little more about the MC3000 internals, I recall from the HKJ teardown photos the MC3000 has a standalone bluetooth module bolted onto a serial port of the main MCU, ie they have not used a main MCU with integrated bluetooth like the ESP8266/ESP32 or the nRF5X. That standalone-module-bolting approach is bound to result in less stable/reliable Bluetooth operations than with one integrated in the main MCU, so it’s possible this Bluetooth-failing-to-respond issue is kinda to be expected.

Terrifying! I’m glad nothing bad ever happened, but were I in your shoes, I would stop doing that, no need to keep pushing your luck.

You’re more than welcome, my friend! Yes, I try and use the app most of the time as it’s incredibly convenient, but sometimes I need to use the charger’s panel too, specially when I’m working on my MC3000 logging program (still a WIP) in order to double-check its results.

So, today I did a different test and got another IR-related piece of weird behavior: with the same batteries on slots #1-#3 plus a second Wurkkos 18650 3000mAh battery (exactly equal to the one on slot #1) on slot #4, this time I’m doing a refresh operation on all 4 of them and also I did not do the initial IR measurement on the charger’s panel (by pressing the up and down keys together), and now the MC3000 has measured and is displaying the IR values for slots #1-#3 (instead of just for slot #1) but NOT for slot #4. WTF!?

This is all being done with firmware v1.18 (for which I’m still collecting data), wondering whether it also happens with v1.15 which seems to be the one most used among the user community.

Thanks for sharing your information about firmware v1.18.

As I mentioned in the other MC3000 message thread (I previously was on firmware v1.15, then updated to v1.18, so I didn’t have v1.16 or v1.17 to test), the IR value appeared too low. It wouldn’t match all the measurements I’ve been jotting down with my previous results.

I understand as the charger ages, and contacts get dirty, the contact resistance (IR measurement, via simultaneously pressing the UP and DOWN keys), will increase a bit.

Another thing is, you mentioned testing the IR of Wurkkos 3000mAh 18650, which are button-tops. In my experience, it’s always more difficult to measure resistance for button-tops due to their smaller contact (button) with the charger. So, if I get a high IR reading with button-top, I usually rotate or reinsert the battery again and again to try getting a lower (but still fairly consistent) IR reading.

I would suggest testing higher drain batteries (with clean flat contacts) to test the consistency of the IR resistance reading of the MC3000, since the readings usually be much more consistent. (at least with my experience of the MC3000. I own 2 MC3000s, an early version with 1 fan, and a newer version with 2 fans).

My earlier MC3000 (bought 2017) seems to have increased IR resistance reading (the springs are not as “springy” as my newer MC3000 (bought 2020). My earlier MC3000 now generally shows a bit higher IR than my newer MC3000. So I’ve been using the newer MC3000 for jotting down IR readings when testing out various batteries. Although for capacity testing, they still have similar results (my older MC3000 actually gives slighlty higher capacity readings, maybe up to 3% or so) when doing the same testing).

side note: I think my newer MC3000 capacity test tends to read a bit low (tend to be lower than the capacity rating, whereas my older MC3000 matches capacity rating more closely)… These are with firmware v1.15, by the way. I have both units MC3000 running v1.15 (I didn’t try updating the older MC3000 to v1.18. Whereas for the newer MC3000 which I temporarily tested v1.18, I’ve reverted it back to v1.15. (I don’t use Bluetooth to control the MC3000, though I’ve tested it seems to work before). Occasionally I connect it to my Windows PC when I want to see discharge graphs.

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Thanks for the detailed and thoughtful reply.

Good point re: using flat-top batteries for more consistent IR readings during testing; My MC3000 has the “knobbly” contact terminals:


And indeed I’ve noticed that some button-top battery model/sizes (notably Eneloop AAAs) do not touch these contacts as well as they should (ie, their button-top touches the knob in the charger “sideways” and not fully face-to-face (what I do with them is to place them “in the air”, so as to touch both poles of the battery directly – has the disadvantage of keeping the battery away from the charger temperature sensor, but with NiMHs and AAAs I think the risk of thermal issues is pretty low.

OTOH, I’ve checked and my Wurkkoses 18650 do make good, full-face contact of their button-tops with the knobs in the terminals:

; from the way they touch, I don’t think a flat-top would be able to make any better a contact.

But anyway, besides the button-top Wurkkoses, I’m also testing with my LG MJ1s which are both flat-top and higher drain (10A CDR), and will keep that in mind what you said when comparing results.

I see myself doing the same in the not-so-distant future, as I’m seeing other weird behaviors with my MC3000 since upgrading to 1.18; my plan is to collect some more data with 1.18 and then downgrade the firmware to 1.15 and do some more tests; if they look good, I will then keep the charger on 1.15.

One question: what do your chargers show for “HW Version” (which can be displayed by holding the SETUP button on the TOV to enter the GSV and then the down-arrow button to scroll all the way to the bottom)?