Charging Li-ion to 4.1X v

oSv

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Undercharging of li-ion is very popular them for discussion.

There are a lot of topics on the Internet with such words:
"I bought a charger, it charge to 4.1x volt is it faulty?"
"My expensive *BRAND_NAME* chargerer charge only to 4.1x. Should I send it back?"

Is undercharging so bad?

I have used many different chargers for the last few years. Nitecore i2, F1; Miller ML-102v8/v9; Xtar MC1, MC1 ANT, SP1; LiitoKala Lii 100. None of them charge batteries exact to 4.2v. LiitoKala Lii 100 overcharge to 4.24v and lowest voltage was in Nitecore F1, just 4.09v. All other charge from 4.15 to 4.18 volts. (I mean charger cutoff voltage, not battery voltage after charging)

Then I thought about it. Is there a charger with cutoff voltage at exact 4.2v? I began to search and came across an interesting article on Tesla's website
This post was published more than 10 years ago!
https://www.tesla.com/blog/bit-about-batteries

It says:

"Voltages over 4.15V/cell (about 95 percent state of charge [SOC]) and voltages below 3.00V/cell (about 2 percent SOC) cause more stress on the insides of the cell (both physical and electrical)"

"There is a huge difference in cycle life between a 4.2V/cell charge (defined by the manufacturers as “fully charged”) and a 4.15V/cell charge. 4.15 volts represents a charge of about 95 percent. For this reduction of initial capacity (5 percent), the batteries last a whole lot longer. Unfortunately, further reduction of charge has a much smaller benefit on cycle life."

a huge difference in cycle life between a 4.2V/cell and a 4.15V/cell charge
the batteries last a whole lot longer

What does that means? How many more cycles? dozens? hundreds?
Is this relevant for modern high capacity batteries like GA, MJ1,
35E ? Does anyone have the experience of cycle to cycle overcharging or undercharging? How does this affect the batteries in real life use?​
 

Modernflame

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I'm also looking forward to some expert input here. Since I stumbled across similar findings about a year ago, I never charge my cells beyond 4.15, usually no more than about 4.12, although I do have chargers that will push li-ons to 4.2 However, it's only been a year and I have no way to measure or verify any improvements to the longevity of these cells.
 

archimedes

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I usually take my batteries off early for torches, as I almost never charge up Li-Ion to max.

After I found my laptops and mobile phone batteries ( routinely charged up to 100% ) losing capacity early, I have since switched to using a timer to keep them typically at or just under 80% SoC ....

Should really be able to custom set "max" state of charge, in my opinion.
 
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stephenk

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I tend to only charge to 4.2V if I know I'm going to be using the light within the next 24 hours, or need to balance batteries for use in series or parallel.
 

oSv

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In some laptops and phones there is an software option that limits charge to 80% or 90%. But is it so necessary?

Typical 18650 rates to 500 charge/discharge cycles. Let's took half - 250 cycles.

Let's imagine that I use flashlight 8 hours every night (full night) and have only one 18650. Zebrlight SC63w and NCR18650GA. I use medium mode 60Lm/33hrs. So I need to charge battery every ~4 days.

250 * 4 = 1000 days = ~3 years to reach half rated cycles!

Otherwise if I have 3 batteries and use charger twice a week (replace battery in flashlight twice a week) it will take ~8 years!!! to reach half of batteries rated cycles.

3 batteries * 250 cycles each = 750 cycles / 2 cycles per week = 375 weeks = ~94 months = ~8 years!

For such long periods of time, lithium aging will have a much greater effect on capacity than charge/discharge cycles, I guess.

I'll just take the batteries to recycling in "X" years and will buy new. But why are so many people worried about this? Why Tesla worried? Maybe batteries are aging much faster if they are connected in packs?
 

oSv

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English is not my native language. I easily read and understand speech, but it's hard for me to write correctly, especially on technical topics.

Maybe someone can send email to Sanyo or Samsung or LG or other lead manufacturer with a request to explain more detail batteries wear.
 

archimedes

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Specialized replacement battery packs may be very expensive, and there now also seems to be an increasing trend towards integrated (non-replaceable) batteries :(
 

herektir

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Battery university has some tables where tests were done concerning this. Charge/ effective full cycle count : 4.25v/200-350 cycles: 4.2v/300-500 cycles: 4.1v/600-1000 cycles: 4.0v/ 1200-2000 cycles. For me this is important when it comes to my iphone. I tend to keep a cellphone for about 4 years before replacement and it has never been for a weak battery. Charging every day 365x4 is 1400 or more cycles before it gets replaced. I try to get my phone to 90 ot 95% state of charge and not go below 30%, but then if they allowed USER REPLACABLE batteries i wouldnt worry about it so much. For flashlights 18650 and 14500 which i use i dont worry about it so much as i maybe put 20 to 40 cycles a year on a battery.
 

WalkIntoTheLight

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One benefit of fully charging to 4.2v, is that flashlights with FET drivers will have greater output. At least, until the battery depletes down to a lower voltage. Even without a FET driver, I've noticed that a lot of high-powered "constant current" lights still drop quite a bit in output as the voltage goes down.

I like keeping a fully-charged cell in a thrower (programmed to a single mode of max). Because, with a thrower, I want full power!

For EDC, not so much.
 

ven

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I have some pany A and pany A cells still in use from...........well must be an easy 5 or 6+yrs. Its that far back i can not remember. Not noticed anything untoward and all my cells are charged to 4.2v or there about. I dont recall any of my cells ever being bellow 4.16-4.18v after being left to sit a while. Although charging to a lower V may benefit these cells, they are so cheap and usually surpassed 12m on.

Certainly having a charger that can be pre set to 4.1v helps, even taking off the charger before terminating. But for me, the inconvenience is not worth it. Cells that dont get used are stored at a lower V if its months not weeks between uses. Other than that i simply charge up, use and swap out then rotate. Cells age anyway, so i would rather cut down my stock and use the ones i have,rather than sit on many for long term(years). I have been using more cells rather than keep buying new, so now my stock of stored 3.6-3.8v cells are around 20. I should be good for a bit flashlight wise(vape cells get replaced quicker). I dont want a pile of sony vtc4 when i could have vtc7's basically(example).
 

ven

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Buy some 4.35v li-ion cells and only charge them to 4.20v no special equipment required.

John.


I have actually done that John, with my KeepPower 16650's in work for my surefires. I have the sanyo 16650(naked) cells in use, these are still charged to 4.35v .
 

TinderBox (UK)

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I have actually done that John, with my KeepPower 16650's in work for my surefires. I have the sanyo 16650(naked) cells in use, these are still charged to 4.35v .

I was charging the 4.35v 18650 you gave me today, Thanks

Trying out my new MiBoxer C2-3000 charger, charging every nimh and li-ion i can get my hands on, It`s very gentle on your battery`s in auto mode, the remaining time function is a total waste of time as it gets the time so so so wrong, best ignored.

Good value at £19 with a 3 year warranty.

John.
 

ven

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Welcome John

Been checking a few chargers out, the dragon and mc3000 still seem up top right now. Still cant decide on what to get next..........
 

TinderBox (UK)

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Not a big fan of the display on the dragon, looks like you can only see 2 channels at a time, and i rarely use my mc3000 as it`s massive and i cannot keep it out or my cats will get it.

I am looking at the Gyrfalcon All-44 or the Nitecore SC4

John.
 

ven

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Yes agree on the dragon display, not keen on it not having a low charge rate either(for my smaller cells). If you decide one day the mc3000 wont get used, i may be tempted to buy off you(no rush)

The 8 channel gyrfalcon would come in handy for me !
 

terjee

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If anyone seriously interested in batteries is not sure which charger to get, and the MC3000 is a candidate (not ruled out by price), then get it. Simple as that, IMHO.

I've become a bit of a collector I guess, and have the Gyrfalcon All-88, SC4, and a bunch of others.

Don't get me wrong, my impression of the SC4 so far is pretty good as well, and I just ordered a second one. It does what I need to do as a matter of routine pretty well, such as charging 18650a and Eneloops, while keeping an eye on internal resistance.

There are things it just won't do though, that the MC3000 does, such as charging to 3.92V (or most other voltages within range) when I take a battery out of rotation.

Edit to add: with the SC4, i haven't checked termination with Eneloops, but it charges the cells without me noticing a worrying temperature increase, so I'm carefully optimistic. It'll also default to 2A on 18650s, which is fine for me, but might be a bit high for some batteries.
 
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