How far can LiIon be discharged?

Thanks HKJ. Again advice we should all heed.

Great info! Thanks

I would suggest “How far can LiIon be discharged? (detailed answer)”

Thanks for this interesting data HKJ.

I've recently been giving some advice on FastTech's forums to certain users concerned about the safety of using unprotected batteries on single-cell (1SxP) buck driven led flashlights. Since the absolute minimum voltage a typical (Cree) led would drop for any current to flow is 2'5V (checked XM-L/XM-L2 datasheets), my conclusion is that it is pretty safe. It must be understood that, as we approach that voltage, current flow diminishes exponentially: it'd take “ages” to reach there (and it would be undeniable to notify on the light's output.

It is a bit surprising to me to see such a jump between load and “no-load” (voltmeter…) voltages in your measurements for that current flow, because that would mean there's close to 0'4Ω of resistance among:

{ R = (Vnoload - Vload) / I }

  • The battery's internal resistante (supposedly lower than 0'4Ω).
  • Whatever stuff between the battery terminals and your readout locations… ?
  • Am I missing something?

Hope the expounded above helps.

Regards,

Salvador

This question is asked a lot on the forum so will ask here.
If the batteries voltage is measured less than the recommended minimum does it make any difference to the chemistry and safety of the battery if its discharged below the limit very quickly or slowly, for eg in a flashlight that has very low parasitic drain?
Many are tempted and it is often mentioned that it is safe to recharge a battery if it has been drained below the recommended voltage slowly.
Hope that all makes sense.

Draining slowly mean the battery spends more time at the lower voltage, i.e. more damage.
But as I say above the 2.5V or other end voltage is not the danger limit.

Well, I’ve barely read a thing about those Nyquist plots, yet anyway, that explains “everything”. Thank thee. In such a case, that just confirms (my) the predicted safety of using single (1SxP) buck driven li-ions led flashlights because of their minimum (led) Vf, which coupled with the intrisically higher internal impedance of the battery when approaching that low Vf… means it is even more difficult for the battery to reach “that low”. Hope this is understood my dears. :laughing:

Cheers

What would your advice then be for discharging phone batteries to ensure a proper calibration of them?

For instance, I am using an iPhone 6 Plus. I read that the battery should be completely drained once per month. However, I read online that it is unwise to completely discharge the battery (run the iPhone on max brightness and play a video with max volume till it shuts off).

I, for now, don’t let my battery drop below 10. I just wonder how I can fully calibrate it by letting the capacity of the battery drain fully so I can charge it from 0-100 and have the highest accuracy of calibration for the said battery.

You only need to calibrate it if your believe the remaining time is far off.
A full discharge/charge will allow the fuel gauge to recalibrate itself, these chips are counting mAh into and out of the battery and this will go out of calibration over time. Some of the newer chips can also correlate with battery voltage and do not need much calibration.

I’ve not done a “battery calibration” for months on my XT1032, and still it shows me accurate enough charge estimations… :sunglasses:
I minimize battery wear by not charging it above 60%, generally. See here:
BU-808: How to Prolong Lithium-based Batteries
Additional information: in the article it is reported that, for 4’2V maximum voltage li-ion chemistries, 3’92V or below no-load voltages are reported to do away with all voltage related stresses. 3’92 / 4’2 equals 14/15 so I’d use this fraction to determine/estimate this equivalent voltage for the now commonly used higher maximum voltage ICR chemistries (commonly used in modern mobile phones).

Stupid myths and [censored] seem to abound everywhere. :person_facepalming:

Your device’s battery is completely firewalled through its power management circuitry. That means in no [censored] way will it allow the battery to be over-discharged.
I bet the lowest no-load voltage your phone’s battery has ever seen is fairly above 3V. I’ve never seen below 3’1V (load voltage, which is always higher than no-load) through my battery monitoring software before a forced low battery system shutdown.
What is more: what you call a “charger” is not really a charger but, usually, just some kind of more or less capable constant voltage supply with @#$% gimmicks.
The aforementioned power management circuitry inside your device decides what/how and when whatever crap is done: “negotiates” power input with the PSU/charger for up to the required amount, feeds the device’s internals and then uses the remaining power to charge the battery.

How could they, the manufacturers, gladly offer the kind of device warranties you seem to enjoy in these iCraps, Crapdroids, Wincraps, etc. in the hands of uneducated [censored] morons without this kind of sophisticated power management? :person_facepalming:

Well, hope this is properly understood. Maybe I should write a sticky about this somewhere, for the love of @#$%…

Regards,
Salvador

Yes, I meant exactly that. According to the previously alluded article at Battery University, just around 58% of remaining battery capacity is held at 14/15th of maximum charge voltage (3’92 out of 4’2V).
My battery is a 3’8V nominal unit, and, at most, I see just below 4’33V full charge voltage. At 60%, I can guarantee you I’m obtaining 4x the estimated battery life expectancy since for every reduction in (nearly) 0’1V maximum battery voltage it is estimated the cycle count doubles. So I attain 8x the cycle life at above half of the useable battery capacity: guaranteed 4x typical battery life expectancy.
And no, it is not inconvenient for my optimized rooted system: I consistently attain above 3 hours of SoT (screen on time) with just ½ of the battery capacity.
Moto G 2013 XT1032 running stock über-optimized “Crapdroid” Lollipop v5.1.
Hope this helps. :cowboy_hat_face:

Cheers

How do you get it to stop charging at a certain percent?

Thanks HJK for the info :slight_smile: it seems that the cells fall-off at the 3volt average mark then rapidly dropping to the 2.5 volt, but the rebound is quick when the load is switched off.

Yes thank you HJK. I wonder why low voltage cut off is not at 3volts? No real power left so flash lights should shut down to save the cell

That’s none of my business. :crown:
However, what they say about battery life expectancy, cycle count, etc is something which matches my (limited) own real life tests, even if these lack any validity and or credibility to you. Thus, go out there and continue using your batteries as the rest of humanity, you’ll be more avidly feeding the related research & manufacturing industry. Thank thee. :face_with_monocle:

Regards,
Salvador

Thank you HKJ!

It doesn’t stops; my cooked solution is to use some kind of software (Battery Monitor Widget) to trigger an alarm when certain conditions are met, so I exactly know when to unplug the PSU brick. In this case:
batt% >= 60 AND Plugged

An added benefit of my policy is that I can minimize the time I have to spend “plugged” because my device nearly always charges the battery in CC mode as, at these charge estimation levels, maximum battery voltage is never reached and thus charge current flow is never dampened.
Most efficient battery management policy. Period. :cowboy_hat_face:

For the sake of completeness:

Hope this helps.

Cheers

Thanks a lot HKJ, article Sticky’d.

I’m a little nervous now after reading this thread…

I frequently use my Olight S1 with wand attachment as a night light for my kids. The other morning I woke up and the flashlight was off due to the battery (CR123A) being totally depleted. Did this damage the battery or simply lower the life expectancy of the battery? Or both? Neither??

Can I use the discharged battery again?

A CR123A is a primary battery and cannot be charged.
For a rechargeable LiIon you need to check the voltage, if it is below 2 volt it is safest to recycle the battery.