Interestingly though…IIRC, SKYRC made the IR resistance change in response to what they thought was a problem with the measurement in earlier versions. I agree though, having compared the IR measurements with 4 wire testers, it is close enough in 1.15.
Let me just put a finer point on what I posted earlier for clarification. If the measurements in a later version than Ver. 1.15 are indeed in the neighborhood of 400% different than those obtained w/ Ver. 1.15 (which from the above posts appears to be the case), based on what I posted earlier about my own observations and comparisons with HKJ’s numbers, it is the newer numbers I would consider suspect, not the numbers I’m seeing w/ Ver. 1.15. Like I said though, if any new concrete, empirical, verified data comes to light which conflicts with that view, I hope it gets posted here, because that would indeed interest me and potentially change my view of the matter. In this case, I value numbers over words.
Speaking of ‘numbers’, just for grins I re-checked HKJ’s test of what were ostensibly the same cells I listed my test results for in my above post; albeit the former is from a number of years ago (unfortunately HKJ doesn’t date his test reports). If you look at his results linked here, while the capacity numbers in his results are much closer to those of my MC3000 than those reported by my Opus, the opposite is true of his internal resistance measurements, which correspond more closely with those of my Opus.
I can say that although HKJ’s internal resistance numbers are generally (just from casual observation) very close to those I see for similar types of cells with my MC3000, that was not really the case in this particular instance.
Suffice it to say this leaves some questions unanswered with full certainty, so I should add a pinch of salt to what I stated earlier, and current empirical data like that posted by @d_t_a and others may be the most definitive. Unfortunately I don’t have the setup to do same-time same-sample testing w/ a proper standalone 4-wire setup, and that’s really what we’d need to nail this down (reference to a known independent standard).
But, isn’t the real question whether the 1.15 firmware shows IR that is closer to actual values than the later 1.17 and 1.18 firmware values?.
I tend to think that none of the chargers with the slider type of contacts give highly accurate and more importantly, repeatable IR results. I can just remove and replace a cell, or hold pressure on the contacts while measuring, and get significantly different measurements. I tend to use the IR measurements from this kind of device as a rough guide, not definitive measurements.
I’ll get back to you when time allows.
I think we’re more ‘talking around each other’ than in fundamental disagreement (with one possible exception).
The objective is singular, and simple: relatively accurate measurement of cell internal resistance.
There are several factors involved in achieving that objective. My comments have not attempted to address all of those several factors. I will expand my comments to address all of the several factors involved in achieving the desired objective. That is beyond the scope of what I intended to address in my comments. I will expand the scope of my comments to include all of those factors, including those which you have raised, but which I did not (attempt to) address. I’ll need to complete one ‘experiment’ to do that, so stand by and I’ll gladly do that. We can then discuss the full scope of all of the several factors involved in achieving the objective.
I noticed in the section “Firmware” here:
https://www.skyrc.com/MC3000_Charger
It seems 1.18 is the latest version (2023-05-25) but is only available for Windows…
How can I update to 1.18 on MacOS Sonoma 14.0 ? There is one MacOS download but its only 1.15 (2020-03-30)
You can’t. You can run Win10 in a VM and install from there, though.
OK thanks, does the mobile app (Android / iOS) have the ability to update firmware?
No
Not sure of the accuracy, but I found the following over on CPF in the MC3000 thread regarding firmware V1.18:
“In a video review they told there is an improvement in bluetooth (I didn’t understand how they can assert this), moreover the bluetooth MAC is now shown in the menu. Instead, no changes about the unrealistic IR low value found in release 1.17.
Then I will stay with 1.15, although I would like to get more information about the changes about bluetooth. Unfortunately at the moment it is quite unreliable.
I find incredible this kind of slovenliness of SkyRC that does not publish any firmware release notes.”
FWIW
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So far I’m still on 1.18, and anecdotally I’ve been seeing values very much in line with what I got from 1.17 (the version the charger came with).
RSN I plan on downgrading to 1.15 and accumulate more data, and then put all the data in a spreadsheet to make some comparisons. But @Desertcat already published very good data right here a couple of posts back, and I don’t think I will find anything very different from that.
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Thanks!
IIRC, V1,17 was where the IR differences were noted. Anyway, I will be very interested to see your results. Still hanging with 1.15 here until that happens.
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Just saw a weird behavior re: IR measurement on my MC3000, posted in a separate topic: SkyRC MC3000, weird IR measurement behavior with firmware 1.18
Reposting here for the folks that might be monitoring this topic but not the “Charger” category.
And then I saw another weird behavior, please see here: SkyRC MC3000: *dis*charging an Eneloop AAA never ends?!
Are there any clever tricks to getting 21700s into the bays? Its such a tight fit I feel like I am always close to bending a slider, and its just a total pain. It simply wouldn’t take my Vapcell F56, even though its a flat top.
This is interesting. I don’t have any of the F56 cells, but with any other 21700 cells I have had not had any problems with fitment. Well, any 21700 other than the few I have with the USB charge port on them. They just do not fit, period!
As to technique, I hold the bottom contact all of the way back with one hand, then try to fit the cells in straight down (so that the are as perpendicular to the contacts as possible). Putting them in at any angle (sort of diagonally) actually increases the required clearance.
I am not sure how much it matters, but the MC3000 that I use is an older one. Maybe the original version, and I have had to do the spring fix when the crappy posts that retain one end of the spring all broke over time. It does have a different contact configuration than the new ones. But if anything, the spring tension is higher because of the way that I had to fix the springs.
Ouch. What do you do then, use another charger (or the built-in USB charge port)? But anyway, it wouldn’t have hurt for SkyRC to have made the slots just a bit longer.
I got an F56 and it fit just fine in my MC3000.
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Weird, according to Vapcell the F56 is just 71mm +/- 0.3mm long: https://www.vapcelltech.com/h-pd-189.html
1.3mm over the standard 70mm shoudn’t be reason for a charger not to be able to fit a battery…
The charger was designed in 2014/2015 when 21700s weren’t commonplace