After reading that 80% of original capacity is a good guideline for determining when a cell’s useful life is over.
I don’t have a clue as to how to do that. Will someone give me some info?
Thanks,
Jerry
Jerry,
It seems like you are trying to determine capacities of your used batteries in order to make a decision if you should replace them or not.
You can look up the original capacities of most commonly used batteries by searching this forum or by browsing some reference resources such as these:
You would also need to measure the remaining capacities of your used batteries using an analyzing charger such as Opus BT-C3400 V2.1:
Then you would use this formula to determine the remaining capacity percent:
Remaining capacity percent = remaining capacity in mAh as measured by analyzing charger/original capacity in mAh as listed on BLF web site.
For example: if an analyzing charger reads the remaining capacity of 2405 mAh and the original capacity was 3200 mHh, the remaining capacity in percent is 2405/3200 = 0.7515 or 75.15%
I hope this answers your question.
Analyzing charger, or discharge tester, that, and knowing the originally specified cell capacity, which you can usually work out from the cell model.
That said, I’m not sure that 80% guideline is particularly hard & fast. Its more a standard benchmark for comparing cell durability.
Also consider that in addition to remaining capasity you may want to know how well the capasity is availible. I am taling about internal resistance. as a cell ages its resisitance goes up. So for the same reasoon we solder copper braid on to hi resistance springs to squesze max performance out of a ligh one will want to consider what the batteries resistance is.
a wonderfully inexpensive charge (less then the cost of a resistance tester alone) “Test/Review of Charger LiitoKala Engineer Lii-260”
Will also give you a mean resistance reading.
Also consider the if whether you draw a line at 80 or some other perceange of max consider that the remaing “juice” is still there. Very few of us would always go to the gas station when we were down to 80% fuel in our tanks.
The nature of cells is a balance, over charge the voltage the risk of damage goes up, under charge they last longer but have less run time in each use. Run them too low and risk cell damage again, dont run the cell long enough and one has a shorter run time again.
Thanks, All,
I assumed one had to have a special piece of equipment, I just did not know what. I do appreciate the information, and now I know what to get if I have that much “wonder.”
Regards,
Jerry
Why can’t you use a cell after it is below 80% of the original capacity?
The other answers are good, so I’ll just add a little bit. If you use an analyzing charger (such as the Opus or LiitoKala) to determine your current capacity, you should realize that these numbers are skewed and only compare really well with results from the same analyzing unit.
Ideally you’d measure the cells on that unit when new, and then again later once they were worn.
It’s just one potential indicator that the cell is approaching the end of it’s useful life. Many cells will “fall off a cliff” at the end. Depending on the chemistry there really may not be an indicator like “oh it’s down to 80%” though. In some cases Internal Resistance may go up before the end I think.
In general I think that once the cell is useless it will have both low capacity and high internal resistance.
+1
I almost never use li-on batteries. At the cost of AA and AAA nimh batteries I think if they seem to be weak I will just throw them away. I realize that if one has a lot of batteries, and the cost of li-ons the analyzer is well worth it. However, I don’t really have such a need. I am grateful for the information, and help.
You guys are great. 
Jerry
I’m with you. Generally speaking if a person is actively using the cells and can’t tell that they have lost capacity, who cares? Nobody, & certainly not the user.
It’s possible that by the next time you go shopping for chargers the analyzing features will be a bit more common.