Newbie trying to measure capacity of cells.

Hey, all. Pretty new here, so keep it (relatively) simple in replies. I checked the other topics, but didn’t really see anything recent about what I’m asking. If there is, though, feel free to point me there.
I have some 18650 pulls from a cordless drill that died. I also have some 18350 and 26650 batteries that I would like to measure capacity on. I have a Xtar VC4 charger that I’ve used to charge these. So my question is, how can I get a good measure for capacity of these cells?
I know the charger shows how many mAh are going in, but its not going to be accurate enough, is it?
I also have an charger from my R/C days, a cheap iMAX B6; it has charging and discharging. Would that be accurate enough? If so, what is a standard rate to discharge at?

You need an analyzing charger that is capable of measuring capacity during a discharge cycle, for example Opus C3100 or Liitokala Lii-500. Sounds like your iMAX B6 might be able to do it as well.

Regarding discharge current, that’s really up to you. My Lii-500 has a max discharge current of 0.5A, so that’s what I use. Just be consistent when measuring one cell vs another so that you have an apples-to-apples comparison.

The Xtar will be ‘approximate’ IF you discharge down to a known 2.8-30-v, then charge it up. It’s not optimal. See what Pete said.

The hobby charger will be better, IF it’s accurate. Lots of the ‘cheap’ IMAX were counterfeit. Accuracy may be fine, may be off. You have to figure that out.
I have an Accucell-6 that is quite good, and a supposedly ‘better’ Turnigy that is theoretically better, at least more powerful, but that one is off 30% in accuracy. Charges, discharges, terminates, etc. just fine but I can’t trust the #‘s it gives me. So……try both and compare the results.
Do you happen to have a [wattmeter]? Putting that in line (you need to make up connectors to ’reverse’ it so it can read properly) is how I discovered that one charger was accurate, the other not.

Standard discharge rate is 20% of capacity. I think the manufacturers often use far less to get better numbers. Your IMAX should go down to 0.1A. I generally use 0.5A for 18650 and 1.0A for 26650, and If they don’t hold up to that, they have other problems than capacity.
I made up a small gluing clamp with leads on the end. Washers soldered to a wire + magnet will also work.