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18650 low capacity cells are safe?
#1
Hello to all, first of all sorry for my bad english. I have some low capacity cells (500mAh-1000mAh). My question is can i continue making more charge/discharge cycles? Or with this low cpacity isnt safe? 

What happen when the cell start loosing all the capacity? like only 1% of the original capacity. Can this be dangerous? Can this make a internal short circuit. Or only didnt make any voltaje?

I read in some post that some bms have a proteccion when the cell reach 300-500 cycle for safety reason and stop working. 

Thank you to all! Nice day!
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#2
Hi, charge cells to 4.2V then check self discharging - give them few weeks and check voltage drop

Exploited battery do not have 1% of capacity because they will have big self discharge or wasting charge current on heat

Cell cycle life is depend from using currents, bottom and top voltage limits, cycle deep, temperature
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#3
The capacity isn't what makes a cell safe or not safe. It's the over voltage/current that does that.

Depending on what the original specs were for the cells, 1000mAh could be 80% health, 50% health, or 25% health. Check the cell database to get the original specs before coming to a conclusion if the cells are worth it or not to continue.
In other words, if the original specs said the cell was a 3000mAh capacity, and it's now 1000mAh, toss it, it's about 30% health and won't last long. However, if the original spec was 1500mAh and it's 1000mAh, then it still has a good amount of life left as it's only 66% health (still low, but still usable in certain applications).
Proceed with caution. Knowledge is Power! Literally! Cool 
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#4
Check the internal resistance too, it might be too high to be useful in a bank of much bigger/lower IR cells. Wolf has done a lot of research on this and is trying to separate out bad cells early by checking IR. Basically, a cell with only 50% of its capacity left will probably have a similarly high internal resistance, which will make it less able to pull out current, and be less of a "contributor" in a large pack, and even worse, will pull out most of its energy when the rest of the pack is depleted, and could cause the cell to overheat or go beyond its specs. I would keep it out of packs with much larger/healthier cells. It's probably ok to make a smaller pack with just degraded cells around the same IR/life remaining as itself, and use it for low discharge applications.
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