Battery Charge Limit ~ Voltage

[Brian_Gregory]

If I tell my Laptop 13 to only charge to 70% is that going to stop it charging its battery to over 4.2V per cell?
I do not like the idea of trusting that a battery manufacturer claims its cells can stand 4.4V without danger or harm to their life. Most normal cells that are only charged to 4.2V last much longer if not kept charged to nearly 4.2V too much.

[inffy]

No it wont change that. It only sets the limit how far the battery charges

[MJ1]

Not sure what percentage 4.2v would be.
Are you on linux?
You can try upower -e then upower -i [battery_path]. It should give you both the current percentage and current voltage, so you can then find the place it hits 4.2v.

@inffy

No it wont change that. It only sets the limit how far the battery charges

Charge percentage is directly related to voltage.

@Brian_Gregory

I do not like the idea of trusting that a battery manufacturer claims its cells can stand 4.4V without danger or harm to their life.

High voltage li-ions are made by all the major li-ion manufacturers. Furthermore, they are in millions upon million of mobile phones at this point. We’d know by now if it couldn’t be done safely. These are not just normal 4.2v cells which are overcharged, rather they are designed for higher voltage.

But of course you will get longer life from your battery by limiting charge. Arguablely less important in a Framework since we can replace the battery easily & at a reasonable price. Unlike most other laptops and especially mobile phones.

[Brian_Gregory]

Thanks for all replies.
I think I will stick with my current policy of keeping the battery at 70% a lot of the time.

@MJ1

Are you on linux?

No, Windows 11.

@anon81945988

… and neither has it helped my battery wear. I have a 12.5% wear after only 103 cycles, whereas the specs are 20% after 1000 cycles.

It seems more likely to me that the manufacturer has been overconfident in the specification of their cells.

[Adrian_Joachim]

@Brian_Gregory

If I tell my Laptop 13 to only charge to 70% is that going to stop it charging its battery to over 4.2V per cell?

Charge limits on laptops are usually based on capacity not voltage, so it’ll charge till the bms thinks it’s at 70% of what it thinks the current capacity is. One side-effect of that is that it’ll gradually loose track of what 100% is because it never hits the top and probably very rarely the bottom.

[Kyle_Reis]

@anon81945988

I have a 12.5% wear after only 103 cycles, whereas the specs are 20% after 1000 cycles.

@Brian_Gregory

It seems more likely to me that the manufacturer has been overconfident in the specification of their cells.

Battery degradation tends to be very non-linear with the first 50 cycles often having a lot of wear. I’ve seen batteries drop to 95% capacity in the first 50 cycles but still have 90% capacity after 500 cycles.

12.5% at 103 cycles maybe seems slightly higher than I’d expect, but may well be within the normal range and doesn’t necessarily indicate that 20% at 1000 cycles on average is overconfident.

[Adrian_Joachim]

@anon81945988

The wording is crucial. Yes the limits are ‘set’ by capacity. However although the applied voltage to charge may be 17.2v the load of the battery, in my case at 78% brings that voltage down to 16.4v. And with me using plugged in most of the time the voltage stays at just under 16.4v pretty much all the time.

What I am saying is it will charge to wherever the voltage goes when it put 70% of the Wh in there that it thinks there are when full. It does not care where the voltage ends up after that (as long as it stays within limits).

If you set it to 70% (so about 42.7Wh assuming 100% healthy battery) and it thinks it has 20Wh now it’ll put another 22.7Wh in there and call it done. So with capacity drift the end voltage will drift too.

[Brian_Gregory]

@Adrian_Joachim

Charge limits on laptops are usually based on capacity not voltage, so it’ll charge till the bms thinks it’s at 70% of what it thinks the current capacity is. One side-effect of that is that it’ll gradually lose track of what 100% is because it never hits the top and probably very rarely the bottom.

I would hope a good BMS would use a combination of voltage and charge/discharge energy along with a typical discharge curve to estimate what it doesn’t know for sure. But you’re right, no matter how good it is, it’s likely to need occasional help in the form of a full charge and a deep discharge.
And I’m definitely not saying I’ll never ever charge it to 100% or discharge it down to near 0%.

[Adrian_Joachim]

@Brian_Gregory

I would hope a good BMS would use a combination of voltage and charge/discharge energy along with a typical discharge curve to estimate what it doesn’t know for sure.

The things are pretty smart these days but stupid real world physics are notoriously hard to model.

[Brian_Gregory]

@Kyle_Reis

Battery degradation tends to be very non-linear with the first 50 cycles often having a lot of wear. I’ve seen batteries drop to 95% capacity in the first 50 cycles but still have 90% capacity after 500 cycles.

12.5% at 103 cycles maybe seems slightly higher than I’d expect, but may well be within the normal range and doesn’t necessarily indicate that 20% at 1000 cycles on average is overconfident.

That’s good to know. Hopefully, my suggestion that “the manufacturer has been overconfident” is largely wrong.
I guess I’m jaded by having recently seen Chinese cells marked 8800mAh that are actually under 800mAh and light as a feather.

[Kyle_Reis]

@anon81945988

Yes that’s what I read but it was under 4% for 100 then went to 6% and then 12% in a week or two

The wear level estimates are also not particularly accurate (they are after all estimates). My prior Thinkpad at one point had the wear level do the opposite of yours and go from 15% to 8% in about a week.

@Brian_Gregory

That’s good to know. Hopefully, my suggestion that “the manufacturer has been overconfident” is largely wrong.
I guess I’m jaded by having recently seen Chinese cells marked 8800mAh that are actually under 800mAh and light as a feather.

Yeah, there are a lot of Chinese cells that are straight up fraud (or sometimes truthful about their capacity but have some other major compromises that make them not worth buying).

[Adrian_Joachim]

@Brian_Gregory

I guess I’m jaded by having recently seen Chinese cells marked 8800mAh that are actually under 800mAh and light as a feather.

If they sell stuff that’s above the fanciest cells from actual manufacturers you can buy it’s pretty much always complete garbage.

[Brian_Gregory]

@Adrian_Joachim

If they sell stuff that’s above the fanciest cells from actual manufacturers you can buy it’s pretty much always complete garbage.

These were included with rechargeable torches (flashlights) I’d ordered.

[MJ1]

18650 batteries?
You shouldn’t use any questionable cells. They can be dangerous. Or any cell included with a cheap flashlight, unless the flashlight is from a known good quality brand. Convoy is one of the least expensive, which is still quality. Convoy Flashlight Store - aliexpress

You can also search for particular features you want in a flashlight here Parametrek Flashlights

For flashlight or battery questions reddit.com/r/flashlight (they are welcoming & friendly there).

If you do buy random cheap flashlights, either don’t get cells with them, or dispose of the included cells and use actual quality cells. If used with questionable flashlights they should be “protected” cells. Li-ion fires are nasty, not worth saving a buck.

@Brian_Gregory

Chinese cells marked 8800mAh that are actually under 800mAh and light as a feather.

The highest capacity 18650s were 3600mAh the last I looked. Anything higher is not currently available from any manufacturer. So a cell marked higher is lying & is usually just straight up dangerous junk.

[Adrian_Joachim]

@Brian_Gregory

These were included with rechargeable torches (flashlights) I’d ordered.

That does not inspire more confidence XD