Expected IR of Samsung 30Q?

To further confuse you, I’ve found that buttontop cells that are fully charged seem to measure IR more closely to the norm—at least on my charger.

DC internal resistance of a 30Q at 4,18V is about 21mOhms.

Here’s an alternate test method. Put them in your best FET powered light and measure the lux or use a clamp meter. Compare to a known good battery of equal charge.

You simply cannot accurately measure resistance of button tops with a charger.

Shoddily assembled button top, 100% sure. I would remove it.

Some chargers (like the Lii-500) just cannot measure internal resistance with fully charged batteries or close to. In case of the Lii-500 the charger needs to inject a current pulse to the cell rail for it to work. Since it cannot go above absolute maximum cell voltage (≈4.2V), if a cell has high enough internal resistance and its voltage is close enough to rail maximum the measurement fails.

If you aim to obtain anything worthwhile out of the Lii-500's li-ion IR measurement set cells to be measured preferably below 3.9V as a general rule.

Wed, 07/31/2019 - 04:46

I dont trust any figures measured by charger, they use only 2 wires to measure IR, so there are many things that can affect number.

Use a proper testing machine, with 4 wires to get rid of any other resistance.

+1 Yeah, it’s not accurate, but it’s good enough to tell crappy cells from good cells. And cheap, too! Just use a brightness app on your smartphone, if you have nothing else.

I have 4 30qs that all perform worse than an MJ1 in direct drive. Lii-500 shows 125 ir. It’s lower when they’re fully charged but still higher than the MJ1. The button is off center so yh it might have something to do with that. Purchased the MJ1 1 year after the 30qs from the same store and the button is centered properly.

You are doing it wrong. See #24 above. When insert and properly seat a fully charged cell in my Lii-500, it shows 10mΩ (it's the minimum and means failure).

The Lii-500 does not display anything higher than 125mΩ. Your cells are probably or surely fakes. If they feature 4 lobe or 4 legged top they're fakes. It could also be that you bought cells with botchily assembled button tops. And it can also be that your cells feature botchily assembled button tops over fake high IR cells. Did I guess the winning combination? O:)

Well it is a trusted seller. I doubt they are fake. The MJ1 I got from them a year later is fine.

If that is the case then the button tops were botchily assembled with really bad welds or absence of. My advice is to remove them. Should be pretty easy.

Cheers :-)

Just received these today…can someone explain to me what the heck is going on here???

Button with pimple tops?

Well it seems like someone’s poked it with a soldering iron. I just wanna know if it’s normal or not.

Those look to be properly spot welded button tops. They should be rock-hard if trying to remove with pliers, requiring careful milling to do so.

If you aim to verify their genuineness you'll need to undress them fully, they look a bit weird from here.


Wow, yeah, someone sure welded the s**t out of those when they put on the button tops. Never seen them like that. I guess they’re okay like that, but seems overkill.

You ordered button tops. All standard 18650 are flat tops, to get button top it is required to weld a button top on the cell. Yours looks like a good type with the button top welded directly to the flat top. It is often done with a strip where the battery and top is welded on and the the strip is folded, this is not as good as directly welding the top on.

Fresh off the charger I managed to get max 8.3 amps in an FT03. Old 30Qs did 6.4

Now try with a Samsung INR21700-30T. Record a small clip so we all can ;-) see later.


The newer SST40s can handle higher current. Don’t know which one I’ve got though.

Well, in this SST-40-W N4 BA test of koef3 it went all the way up to 9.4A in the test bench.

In any case, those living on the edge flashlight setups are not my cup of tea. Not because I cannot take care of them, in fact I take a lot of care. But I'aint got time to bleed. ;-)

Cheers :-)