I tried it once and it added a lot of extra resistance.
Hope not! leomiboxer is the OP of this thread and will probably understand about the tabs. After JasonVW mentioned the problem with the tabs, Leo said the C4-12 tabs will be redesigned in future versions.
I just thought I will share that I have a 3400mAh Panasonic 18650B that was somehow drained to below 2V by an Ultrafire flashlight just for being left in it. My Liitekola 500, 202 and Zanflare C4 wouldn’t charge it again. As batteries were so hard to get into Australia, I held onto the “dead” battery for a good 1-2 months.
Since the Miboxer C4-12 has a wide range of charging current, I decided to give it a try to see if it will revive the battery or not. It started charging it at a miserly 0.1A for quite a while due to high internal resistance, but charging current eventually did increase slowly over several stages. After several hours, it reported the battery as fully charged at 4.2V. I was still rather skeptical when taking it off the charger, but a quick check of the voltage using a multimeter did indicate it is fully charged at 4.2V. Most importantly, it is now working again perfectly in a flashlight. So thanks very much Miboxer! 
Yes, it’s smart enough to also revive my cells, though brand-new, that was inadvertently left at a low voltage of .72v for 7 mos. lt will initially pump-in at .1a and wait for the IR to go down as it proportionally increases its charging rate when it’s safe to do so, automatically.
Some of my cells that were unrecoverable did not benefit from this feature.
If you only have really good cells at your disposal then you won’t be aware or take advantage of this charger’s feature.
Miboxer C4-12 — can change the charge rate on-the-fly (after batteries are inserted), press and hold the button to enter “change charge current”, then single-press to cycle the available charge current selection, the current display will flash if current selection is the “automatic charge current”. Press-and-hold the button to select the current.
Got it, thank you! I'm still having some problems making contact with the larger batteries even after bending the negative tabs, but can get some to work if I lift them up off the base of the charger.
That link now shows $44, personally I’d go with amazon at $49 (actually I did) and get it in 2 days rather than aliexpress and get it sometime this century.
Dude, you qouted a post from Nov 11, 2017. Of course it’s not on sale any more. You have to be quick for those sales. My total cost was $29 on it.
Did you see my post from a few days ago? Banggood $34.
Amazon shows it for $50. So that’s a $16 difference. Some people are frugal with their money and might not mind the wait for shipping.
So we have choices.
£49.99 ($70.96) on Miboxer’s Amazon UK store - £30.67 ($43.55) when I ordered it from GearBest last week. They only had versions with US & EU plug, but several reviewers from the UK pointed out that they received their charger with a UK adapter, so the decision where to buy was pretty much a no-brainer.
There is a code floating around youtube for $34.99 for the C4-12 from Banggood, that's where I ordered mine from a few weeks ago.
We definitely get ripped off here in the UK …
Guys I got this charger off amazon 2018 March along with some Samsung 30Q button top cells from Richards store and the C4-12 ALWAYS gives me 999 milli ohms mesasurements at first, then when I fiddle with the cells I can get lowest 530ish! So either the cells I got from Richard suck, or the charger I got from amazon sucks.
Please help? Any ideas?
Do you have flat top 30Qs? It should be less than 50milliohm range in new…while button tops will add a very substantial, and in various amounts of IR, specially the protecteds.
I have brand new button top unprotected 30Qs. I’ve been fiddling some more with the charger and the cells twisting and turning them, pulling them back but they are still showing 230, 299, 119, 342.
Also on the charger display it doesn’t show the percentage going up. I just now pulled a battery back and it jumped from 42% to 80%.
It’s weird.
Pulled battery back and now it’s back down to 44%. I’m so lost.
Do you have brandnew but not button top, just flat tops and tested their IRs? My conjecture is that the button top may be the culprit.
Some button tops have ends with this nipple (pictured below) just held by the plastic wrapper, not spot welded, thereby increasing IR at highly-different readings that will surprise you.
…and I just checked…now they even have ones for the Negative ends!:
No I for sure have button top cells. I don’t know how to measure the IRs other than with the charger.
Is there any fix if it is caused from the button top?
Brand new from Richards store a few weeks ago.
“INR18650-30Q
SAMSUNG SDI
136”
That’s what it says on the cells if that matters
The C4-12 is too sensitive (when Auto mode is selected) on cells with high IR, that it won’t charge above .3A.
I would suggest to use the Manual mode instead in order to select perhaps 1 to 1.5A charging rate.
I’ve been using manual at 1.5A charge. When I do that though it doesn’t show me the progress or what have you (the percentage charge).
This is what my charger is showing now.
Slot 2, 815 milli ohms, I set it at 1.5A charge rate but it shows .54A charge rate, 49% charged, 4.20V
They are all at 4.20V. But at 89% 86% and 49% charge.
Should I try one of my flat top Efest purple unprotected cells and tell you what it does? Or one of my Panasonic protected NCR18650B cells?
Is the high ohms something to worry about? I was told by another BLF friend that 400 was pretty high for a cell.
Yes, try the flat tops and unprotected but relatively new ones that has IR well below 80 IR