Comment by codys | Hacker News Reader

Comment by codys | Hacker News Reader

The article lists percentages of capacity as if every battery (or battery controller) reports the full range of capacity (or allows charging to actual full capacity or discharging to completely empty).

I had thought that many manufacturers (at least Apple) had added things that specifically limit the amount the battery is charged to less that "100%" while (of course) still displaying 100% to the user (essentially, users see the the capacity as dictated by policy, not by physical characteristics).

Is this article only talking about "dumb" Li-Ion batteries? I note it's a "watercraft" related blog, does that mean the same mentioned percentages don't apply to non-watercraft/consumer Li-Ion batteries?

Further, we get some numbers, but we don't get the data those numbers are from. I presume they are just "these seemed to make sense to us from our anecdotal evidence".

I put a link to Battery University at the end. Some of the numbers came from there. Others come from cell data sheets (best ones from Panasonic). A lot of this is synthesis over many data sheets and white papers, none of which would by themselves be illuminating to the average battery user, because so much of the data would be cell-specific.

You're right that device manufacturers choose what to name "100%". Generally, cellphone makers are most attuned to people running out of power, so their 100% is pretty close to the real top charge level (not overcharge). They are rated and tested and reviewed based on tests like Walt Mossberg's run standard processes and see how long it runs until empty. The incentive provided by such make-or-break tests is to allow users to fully charge and fully discharge.

Better control and information would be provided if you gave the actual voltages and chemistries, but both are beyond what a normal user would be comfortable using on a daily basis. Internally, we almost always refer to state of charge in cell voltage terms.

Tesla and BMW provide the ability for the user to know and adjust the top of the charge. Tesla's approach is fairly user-friendly, and BMW's is a little more powerful, albeit less user-friendly.

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