Correct charge voltage for Samsung 35E

[Valman]

Hi, the datasheet for the 35e says charge voltage is 4.2v, but setting up my isdt t8 charger, it seems to say 4.1v for LiIon and 4.2v for LiPo.

I thought the 35e was LiIon, even the datasheet says lithium ion, so why doesn't my charger not let me set LiIon to 4.2v? Is the 35e actually a Lipo?

Thanks

 

[thunderheart]

but setting up my isdt t8 charger, it seems to say 4.1v for LiIon and 4.2v for LiPo.

Someone at ISDT should be fired))

Is the 35e actually a Lipo?

Of course it's not a Lipo)) BTW, Lipo is Li-ion too.

 

[Valman]

For LiIon I can adjust it as high as 4.15v but no higher. I wonder could there be any downside to me setting it to LiPo to get the 4.2v charge voltage I need?

 

[thunderheart]

I wonder could there be any downside to me setting it to LiPo to get the 4.2v charge voltage I need?

No. Feel free to select Lipo and charge your cell to 4.2V

 

[Pajda]

"4.1V Li-Ion, 4.2V LiPo and 3.7V LiFePO4" is a historical designation used by almost all modeller chargers. All settings are using the same CC-CV algorithm and it only differs in CV charging voltage. This designation acts only as an aid for novice users that LiFePO4 chemistry has a lower voltage than LCO chemistry used in pouch cells (modellers calls LCO pouch cells as "LiPo" or "Li-pol"). And about 15 years ago there was general recommendation in modeller world to charge 18650 cells (modellers calls 18650 cells as "Li-Ion") only to 4.1V. Thats all. :wink:

 

[Valman]

would charging just to 4.1v be better for lifespan than charging set to 4.2v?


I charge at 1.02A because datasheet says that's best for lifespan

thanks for the amazing quality of responses

 

[Pajda]

would charging just to 4.1v be better for lifespan than charging set to 4.2v?


I charge at 1.02A because datasheet says that's best for lifespan

thanks for the amazing quality of responses

It differs cell from cell, for example LG cells in 18650 have excellent cycle life even when charged to 4.2V and there is no significant benefit to charge them to 4.1V. But there are lots of cells which have worse cycle life and it helps to use lower charging voltage. 35E will benefit from lower charging voltage but you will see this benefit after ca 400 full cycles so the questions is if it worth to have 10% lower usable capacity every day.

And 35E is very sensitive on charging current, 0.3C is maximum for good cycle life. 35E cycle life sucks when charged at 0.5C or more. For example LG cells have 0.5C as a standard charging current an there is no significant benefit to charge them slower.

 

[Valman]

Thanks Pajda, the 35E datasheet agrees with you entirely about charge current, it says 1020mA (0.3C) for best cycle life which is what I'll be doing. I have plenty of capacity overhead for my application, so for me I want to prolong the life of the pack as long as possible.

I just read this article https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

which suggests 3.92v to maximise longevity, and if longevity is your sole goal, the sweet spot is keeping the battery between 75% and 65% SoC , but at that point you're losing most of the purpose of having a lithium pack

I'll probably charge to 3.92v as they reccommend, and will generally try and not let the pack discharge too far too often, keeping charge above 50% SoC whenever it's easy enough for me to do so.