I've read Why are(n't) rechargeable batteries damaged by partial charging? and main source quoted batteryuniversity. I found the article having deficiencies and looking to find more "accurate" and scientifically minded studies on batteries charging / discharging effects / performances (that study disclosed sample size for only one of 6 figures/tables/results, no peer-review, it is not a journal publication).
As for the mentioned article, below are several specific questions I'd like clarifying:
batteryuniversity questions for the article:
- for 1st graph they discharge to 3V. What capacity level might it be?
- depth of discharge (DoD). Is it probably calculated here (and usually in technical literature) based on original / nominal capacity or remaining capacity?
- (point cleared thanks to user_1818839 - was my mis-read)
- before table 2 there is a description where "indicated state-of-charge (SoC)" is mentioned, but SoC is nowhere in the following table. What could it mean? IMHO is could mean human error like cut-and-paste, than it is also stated near that phrase that battery is cycled until 70% of capacity is left. What that might be erroneously cut-and-pasted too. Does 70% looks reasonable here?
- table 2 there conclusion of mid-range DoD best longevity is not supported for LiPo - for LiPo table gives 20% DoD 9000 as best (jump 3x * drop only 2x from 40%).
- table 3. They did not test for sub-freezing. Internet jury is out on that. Google search find numerous claims freezing restores capacity, in that QA here discussion is around protection from freezing: What is the effect on lithium ion batteries from long term storage in sub-freezing temperatures?. Any studies on that one?
- table 4. They did not state to what minimal voltage / capacity they discharged. Does it look like that discharge to 0? Cause their remaining capacity column indicate numbers so large for their assessment of decreased remaining capacity that at first glance it looks to me as close to 0. But 0 in many places is said to be much worse that 100% and control boards of devices mostly does not allow it. Does that test adds practical value then? Or from given data you calculate remaining charge much higher than 0?
- figure 5 suspiciously does not have long enough NoC axis for us to see when at 4.2V capacity also drops to ~0%. Where to see more complete graph?
- figure 6. Finally something to cross-check. They have Note near beginning of article "Tables 2, 3 and 4 indicate general aging trends of common cobalt-based Li-ion batteries on depth-of-discharge, temperature and charge levels, Table 6 further looks at capacity loss when operating within given and discharge bandwidths." IMHO it makes people assume Table 2 and Figure 6 analyze same battery types. Table 2: 100-40 (1000 cycles) and 100-60 (600), whereas on Figure 6 for line 100-50 I see more than 90% retention at 1000 cycles. Clearly Figure 6 gives times less loss compared to table 2 for procedures of non-contradicting (some additional info, e.g. temperature for Fig 6) description. It could indicate my guess above of cut-and-paste error above of 70% for table 2, could it? Any other possible reasons?