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Originally Posted by keepinitreal538
https://www.alibaba.com/product-deta...6e6931b5nkxdi2 Smartereveryday, this would be a cheap easy way to test the capacity. that should tell you how degraded the cells are, but someone else will have to chime in to say what range would still be considered good. maybe someone who knows better can say what the best buy is...
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When lithium batteries degrade, they start to degrade faster and faster.
The capacity rating is not the same as what we would consider "the amount of life left" rating.
A battery at 50% of its capacity rating probably only has 15% of its life left before it totally fails. Its not quite that simple but close.
So lets say we have a 100ah battery that's supposed to be good for 1000 cycles. We do a capacity test and find that the battery only has 80% of its capacity (80ah).. Most folks assume that means there's 800 cycle left, but the reality is that its probably more like 300 cycles, and the last 100 of that 300 will be down well below 50% of its original capacity.
As lithium batteries wear out, they wear out faster and faster. This is why most are replaced at 80%.. they know that once a battery gets down that far, its going to pick up speed and degrade even quicker..
This all assumes normal wear and tear on the battery through use, it does not apply to a battery who's life has been degraded due to exceeding the battery's specifications.
In the case of Nissan Leaf cells, almost all these cells have exceeded their temperature ratings and are cooked. How this affects the degradation curve has yet to be seen as most of these cells that are sold on the salvaged battery market go from a hard life propelling a 4000 lb car, to an easy life powering someone's coffee maker.