Charging Li-ion to 4.1X v

[david57strat]

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.

Agreed. I have always felt that the display lettering on the Dragon could be half the size, and show all four channels simultaneously, rather than just two at a time. As it is now, it looks like it's designed for the visually impaired lol.

 

[ArminVanBuuren]

My i4 on the other hand charges it to 4.25v. Is it lethal for the battery, or is is still ok?

 

[ven]

Have you verified away from the charger with another source(multi meter for example). It is right at the spec limit, most chargers are + or - 0.05v, so 4.15v to 4.25v is within spec. Personally i feel its a little high and would prefer a termination V closer to 4.2v. Other option is remove off charger before charge is completed. Inconvenient granted, but just a thought if your in the vicinity.

 

[zipplet]

I have noticed that good quality chargers set to the correct charge rate (e.g. using 0.5A for 18650 is too slow!) tend to result in cell voltages that droop slightly once finished, down to somewhere between 4.15V - 4.18V. Personally I think this is a Good Thing - the cells will last longer. Capacity wise you aren't missing out on much. Someone pointed out that FET drivers may be slightly dimmer; while that may be true the flashlight will quickly drop down in brightness anyway as a change of 4.2V - 4.1V is somewhere around 10% of the capacity if I recall correctly.

If you use a quality charger and set the current too low the cell tends to stabilise closer to 4.2V when finished. I guess people who mind the voltage droop can do this.

Personally, I say accept the slight droop and enjoy the longer life expectancy of the cells.

 

[bob_ninja]

Do you need more cycles is a different discussion. For some uses like flashlights maybe few hundred cycles is enough. However there are other applications where you need/want more:
- EV cars
- phones/laptops
- battery powered robots

My EV car actually has a configuration to choose between 100% and 80% charge limit specifically for longer lifespan. So yes it has huge impact and some EV drivers are starting to supply real life data.

The biggest factor on lifespan is intensity of cycles combined with max charge limit. For EV cars the worst performance was in hot states (Arizona, Florida, California) that have:
1) higher temps
2) intense cycles due to high speed driving = higher power = more heat
3) full 100% charge

So if you drive on highway causing 1C-3C power on battery, then immediately charge hot pack to 100% then drive again, etc You have high intensity cycles combined with full charge and batteries can die pretty early. There are talks about battery behavior and the point was that most degradation occurs in top 10% and bottom 10% (roughly). Meaning if you stay in the 20%-80% SOC range you can easily double or triple or increase even more lifespan.

Again for flashlights it may not matter since LEDs use little power compared to electric motors on EV cars and robots. However for cars and robots batteries can die early. For cars in particular batteries and replacement work is super expensive so it does matter.

Not that it is super important, but if you are using old cells pulled from laptop packs then lower charge voltage can help keep them alive bit longer. It depends on your cell use, how often you use them.

 

[zipplet]

Agreed completely and my own experience mirrors this. I do acknowledge that if the user is willing to take a hit on cycle life for an application such as a flashlight with easier to replace/cheaper cells, then perhaps it is worth having a function added to chargers going forward. It would work by waiting for the charge to end, waiting another 30-60 minutes, and if the voltage has dropped to the 4.15-4.18V range it could then resume charging using a slower charge rate. Nothing unsafe about that, simply a loss of cell life. However it would give people the extra <10% of power that can't always be squeezed in by a fast charger that stops at 4.2V exactly when charging at a higher current.

The 20-80% SOC rule is one I always try to follow for devices with expensive/difficult to replace cells such as certain laptops and my mobile phone. I have managed to stretch the battery lifespan of my 2 year old cellphone to the point that it almost holds the same charge it did when new because I avoid charging it to 100% at night if the battery is >=80%, and charge before it hits 20%. This will be impractical to those who heavily use the phone however!

My Samsung laptop also has an option in the BIOS for extending battery life time. It limits the battery to 80% SOC during charging. I also noticed another interesting quirk: If you charge the battery and then let it drain to say 92% and plug in the charger, it does not charge it. It seems to be some method to extend the battery life.

 

[terjee]

There's no need to wait, really.

If you select 2A on a charger, it'll actually charge in two phases. First a constant current phase, where it charges at 2A. Then, when it reaches 4.2V, it changes to constant voltage mode, and just holds that 4.2V until the current drops to 10% of the initial current. A bit simplified as chargers deviate all the time, but that's the basics of it.

What you can do, if you really want to max out, is to just slide those values around. If you terminate at 20% for example, you'd get some more life. Same if you'd switch mode and hold at 4.1V instead of 4.2V, that'd about double cycle life. Or you could terminate at 1% instead of 10%, and most batteries would hold at 4.2V (or so), and drop down less.

Speaking from (empirical) experience here, the MC3000 lets you do all of these things if you'd like.