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Comment by eqvinox | Hacker News Reader

JFTR: achieving that capacity retention is a question of charge settings. Pretty much any Lithium ion battery can achieve it if you don't charge it to the absolute maximum possible each time.

It's quite simple. While you can charge a "good old" Lithium ion battery to 4.2V, you already start getting slow degradation at that point. Charging it to 4.1V or 4.05V massively reduces that. But at the same time, those 100 or 150mV are a notable amount of charge, up to 20%. So… yeah. It's a tradeoff.

For reference: https://nenpower.com/blog/how-does-charging-voltage-impact-t...

https://e2e.ti.com/cfs-file/__key/communityserver-discussion... page 15

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> JFTR: achieving that capacity retention is a question of charge settings. Pretty much any Lithium ion battery can achieve it if you don't charge it to the absolute maximum possible each time.

Thats great news - manufacturers who want to ship sealed phones have to charge intelligently.

In fact, I'd take this constraint:

> There's an exception for batteries that "retain at least 80% of its original capacity after 1,000 charge cycles."

even further: retain at least 80% of capacity of 5k charges and commit with escrow money to maintain the software for 10 years. If the manufacturer is unable to commit, with money, to a 10 year support cycle, then the must provide at least ability to root the phone without needing manufacturer consent.

It would be nice if manufacturers stopped shipping disposable phones...

Next thing you know, someone on hacker news will be posting about how they reverse engineered their iPhone so they could charge the battery 10x faster! Everyone will complain about Apple being a walled garden and how regulation nerfed their batteries and how we should be in control of the things we buy and be able to modify them…

Every 10% you don’t charge roughly doubles your battery life, scroll down to “The 80% Question”. This applies to Apple batteries, but I suspect most other recent battery are in the same ballpark.

https://randsinrepose.com/guides/apple-charging/apple-chargi...

If the bill defines a charge cycle as 100->0->100 then the restriction should be more meaningful right? Manufacturers would have to ship a larger battery and cap its capacity to get the same lifespan.

100% and 0% are essentially arbitrary, though. That’s the point. What is 100% for a battery? 4.1V? 4.4V? What’s 0%? 3.0V? 2.5V? Lower?

And to add to the confusion, the display reads 100% of the current capacity. 100% of 80%.

Irrelevant for state of charge, though. My point is you can define 0 and 100 as specific voltages and arbitrarily make the capacity larger or smaller. LG was notorious for having the top level charge be unusually high for the time (4.45V or something) which meant they had amazing battery life when new, but quickly fell off a cliff as they aged rapidly.

I suppose they can advertise a 0.9x Wh battery and include a 1x Wh battery instead, which is fine for me. If the battery is going to degrade hard just give me one that only reaches 90% max.

This is probably what Apple is going to do, soft limit the battery to not charge to 100% yet still report 100% in the UI. Many android devices and laptops have such a setting these days already. For some it might not be nice to see 80% after a night's charge, hence the UI fakery I'm suggesting.

My old 2018 Hyundai Kona EV did the same thing: officially it was a 64kWh battery, yet when you count the cells they come out at 71kWh or something. They built in some margin to extend battery life as capacity declines. Coïncidentally this also meant that regen braking worked even when the battery was 100%. The car is at 110,000km and the BMS still reports 100% SoH.

4.05V is 94% of 4.2V. Does that translate to having 94% capacity longer. For a total capacity over time greater than maxing to 100% with an 20% falloff?

You are assuming that a battery is full at 4.2V and empty at 0V. In practice a Lithium Ion battery is empty at 3V. You are also assuming the relationship between capacity and voltage is linear - it is not.

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