18650 and others battery issue (not charging)

[tbone1004]

One battery is at 2444, it has 3000 on the side of the battery.

My "rule" is anything less than 80% is done, many others recommend 90%

 

[Scoooter961]

My "rule" is anything less than 80% is done, many others recommend 90%

ok is that because of safety or because of use life. These are in flashlights that are used for walking the dogs 99% of the time. So I’m not too concerned about them not lasting through the walk.

 

[tbone1004]

ok is that because of safety or because of use life. These are in flashlights that are used for walking the dogs 99% of the time. So I’m not too concerned about them not lasting through the walk.

safety, when they get that low they usually have pretty high internal resistance and a good bit of self discharge which is a potential safety issue.

 

[fmerkel]

Ok so I got the new opus charger and my three 18650 flashlight batteries are 110, 122, and 187 on the quick test. Are they still ok to use and charge?

Reminder:
Because of the inherent resistance of the sliders, internal resistance can be somewhat erratic in these kind of chargers. Consider it to be a rough guide.
Make sure the battery terminals are clean, the battery is well positioned, and it's useful to do multiple test and try different slots.
I throw out the extreme readings and look for an 'average'.
(BTW, this reading is not a 'standard' or 'absolute'. You cannot really compare it to other readings on other devices.)

Industry thinks a battery under about 80% is past it's prime. I'm more liberal than that, BUT, it depends a LOT on intended use. Low grade batteries are lightly used, like in a low output light.
I also have the tools to watch if a battery is showing unwanted deterioration. That may not prevent a serious problem from happening unexpectedly though. At some point there is a judgement call about value vs. safety.

 

[tbone1004]

good point @fmerkel
Mine are all used for backup lights for cave diving, so I tend to be quite conservative with mine, but I also take care of them and only buy high quality cells, so they go for quite a while before they get to below 80%.

 

[Scoooter961]

Thanks again for all the guidance. Here are the results after testing. Would you all say battery 1 is trash and the rest are ok? Also what type 18650 batteries do you buy?

Battery 1
Resistance 187
Capacity 2444

Battery 2
Resistance 95
Capacity 3407

Battery 3
Resistance 108
Capacity 3353

 

[tbone1004]

I would say 1 is destined for the recycling bin.
I buy these
Protected Panasonic/Sanyo NCR18650GA 3500mAh 10A 18650 Button Top Battery - Wholesale Discount

 

[Scoooter961]

What would you use for a cap at the internal resistance? I am going to buy some of the Panasonic's soon as well.

 

[tbone1004]

What would you use for a cap at the internal resistance? I am going to buy some of the Panasonic's soon as well.

complicated given the accuracy of the chargers, but for me personally it would be around 150-200mOhm which should be about double what they are when new. Internal resistance is tied directly to cell capacity and self discharge though, so the capacity tests are what I usually go by. The internal resistance is nice to see on the big boy packs in lights and scooters where it can be harder to get accurate capacity measurements

 

[Scoooter961]

Ok thanks, 2 more questions. How often do you test them and any suggestions on flat top 18650's? From work i don't have the length of the batteries. This is what I currently have and are the ones in question... Battery Cell 18650SKU: BATCELL18650-G | Bigblue Dive Lights