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Comment by jauntywundrkind | Hacker News Reader

I wonder where the state of charge is held here. This could actually help the long term battery life significantly. Do these discharge not as deep? Do they not fully top up? Neither full charge nor deeper discharge are good for batteries. Avoiding those areas could be a long-term win.

It'd be pretty easy/interesting to compare the charge curves & find out what part of the curve it looks like versus a regular capacity model.

This sort of cost-unrelated rent keeping keeps growing. Intel selling you a chip then having the vendor either one time fee or subscription based unlock any of the half dozen different accelerators is another stunning example. That one's even weirder to me, in that it's unlikely people will bake in support for these special features to common software systems, if they don't have access!

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I was wondering this too - and what happens with age? As the max charge level depletes does the artificial limit change, or stay the same?

Great question! If it unlocks more headroom to compensate for aging battery that would be fantastic.

The sensible thing would be for it to stop charging at actual 75% and then as the battery degrades unlock the unused range gradually so it appears like there is no degredation for a decade.

and in 5-10 years your range may match your neighbors with the expensive one.

> That one's even weirder to me

This one actually seems more straightforward to me? It's hard to design chips so it's easier to use a common wafer and then cut features to tier the product.

It's even simpler: it's hard to manufacture complicated things 100% correctly, so it's easier to make the most complicated version and bin/fuse off feature sets based on where the defects are (rather than just throwing out all chips with any defects).

Depends on the battery tech I imagine.

LFP batteries are recommended to charge to 100% every time, where as NCA / NCM are both what we traditionally think of when discussing lithium batteries.

I imagine for LFP they will keep it as full as possible, and hard cap the other types to 70%.

More reading here: https://history-computer.com/which-batteries-is-tesla-using/

LFP batteries age faster when at 100% just like non LFP batteries, but since they degrade slower over time overall, and since you need occasional 100% charges for the battery management system to know what % of charge you are at, it is recommended to charge it to 100% regularly.

if you wanted to protect the life of your LFP battery, don't charge it to 100% every day, just every week or two so the BMS knows what is going on.

For additional context, the reason for this is that LFP cells have a much flatter voltage curve than other chemistries [1], so the BMS is forced to guess at the state of charge by tracking how much current has gone in/out of the battery, which is subject to drift.

1: https://www.researchgate.net/profile/Anupam-Parlikar/publica...

If I had to guess, they probably don't fully top up.

If it’s software locked to below the true battery capacity, then yes by definition they don’t fully top up. Which is actually a lot better for the battery long term. Nice silver lining for these cars. Sure you can do the same by refraining from topping up yourself in a regular model but then you don’t get the price break.

The software lock could just as easily to refuse to discharge below a certain capacity. Or it could be a combo of both.

As I said, “if”, but sure.

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