I have been looking for an article that talks about charging, discharging lithium ion batteries.
I want to know how to determine the best rate of charge and discharge for 18650, 18350 & 21700 batteries when I first get them in order to tell what kind of condition my new batteries are.
Most consumer chargers, save for the Sky RC MC3000, only discharge at 1A for any and all slots, so we’re stuck there.
For charging, both NiMH and Li-Ion batteries, I like to charge at 250mA (16340,) 500mA (14500/18350,) 1A for 18650s and between 1A-2A for the 21700s that I have.
Chris
That helps a lot because I’m buying some new batteries to replace some older unlabeled type (ebay, Amazon) batteries with new high quality batteries and I don’t want ruin them before I get to use them.
I just got some vapcell F14 1400mAh batteries today. What setting would you recommend for these?
Well, the F14 is a 3A (discharge) 18350, so that’s not really a problem. I tend to be a bit conservative, so I’d charge them up at 500mA and discharge them at 1A, just to see.
What charger and what is the discharge cutoff voltage for it, with Li-Ions?
Chris
I have a liitokala lii-m4s or opus BT C3400 but I don’t remember the cut off voltage for them.
I think that you can be safe using 0.5C for charging about any LIION cell. So a 5000 mAh 21700 could charge at 2500mA (2.5 amps).
3000 mAh 18650 at 1.5A. ETC.
Though I have charged cells like 750 to 800 mAh 14500s at 500 mA and never had an issue.
1 amp discharge should be OK too. Check the max sustained current rating for your cell. But few will be under the 1 Amp level.
I typically set the MC3000 to stop the discharge at 2.8 volts. This may be conservative, but the cells have little left at that voltage anyway.
You can find the data sheet for the cells that you are using and it will give you all of the particulars for that cell.
Thanks, the information really helps.
I just finished my discharge of my 2 Vapcell F14 they were 1453/1455. I am ok with that.
Agreed. The C rate is really what you’re looking for, rather than specific current.
It might not be known or clear what cells are underneath the wraps of re-badged cells… so you won’t find a datasheet. Unless the cell is particularly weird, you can use a C rate of a similar size/chemistry cell.
True… but quite often a bit of research can find what cell is under the re-wrap. Worth the research IMHO. If not, usually the Capacity (C) is listed on the wrapper… so the general rule applies. 
One of my F14 batteries just finished charging and it reached 1549mA, that’s 110%. The second one is still charging and it’s at 1613mAh’s which is 115% of the claimed mA’s. So I would say these met their claims
You need to check capacity on discharge, not charge. You will always put more in than you can ever get out.
I did, they were 1453 & 1455. I’m still happy with the results. I am only using these batteries as a backup to my backup batteries in my emergency bag.
This site has been my go-to for battery info for quite a while now. There is a TON of information and it’s organized well.
For charging specifically, check out this article:
Until you get up around the highest capacities for that battery format kinda. As in, a 3500mah 18650 would generally prefer a lower C rate than a 2000mah 18650. But I’m probably just needlessly complicating things now
@Jeffgoldblum I’m checking 2 N36 vapcell batteries that I just got today.
Last week I got 2 Panasonic/sanyo 18650 10A 3500mAh & 4 MJ1 10A 3500mAh batteries and they all came in at or above the claimed mA’s when discharged. I still have a lot of batteries to buy because I’m getting some for my kids to have on hand in an emergency.
That’s cool. Oh, something else to maybe consider besides the battery’s rating is the temperature your setup gets to. Idk what you have, some of the chargers that double as dischargers will get real hot even at a low discharge, especially if you’re doing a few at a time, then that heats the batteries. They can be 60°C+ during discharge and you’d be fine, but it’s something to think about. Not a bad idea to try and keep it lower if you can. You’re limited by the charger as well as the battery in a way.
I have an opus BT C3400, liitokala lii-m4s and a xtar vc4sl updated. I mainly use the opus and liitokala. I don’t really get any heat with opus but I do with the liitokala and so I keep the charge and discharge at 500mA or lower.
Just to clarify the “C” that I was referring to is Capacity. So the Charge rate in amps (lets call it lower case c) is a percentage /decimal multiplier for the capacity rating… in Amps. When dealing with acronyms or letter designations in a formula, it is important to define the terms to avoid confusion.
For (just to simplify) a 2000 mAh (2 amp hour) cell we multiply 2000 X 0.5 and get 1000 which translates to 1 amp of charge rate (c). For a 3500 mAh cell that would be 1750 or 1.75 Amps for the charge rate (c). I still generally use 1 amp for these. But 1.5 would be acceptable.
So yeah. I tend to charge lower capacity, meaning between maybe 1500 and 3500 mAh cells, at 1 amp. Beyond that, and even the 32650 6800 mAh cells) I use 1.5 amps. Unless I am in a big hurry and am willing to trade cycle life for speed, then I may use 2 amps (even though the charger can charge at 3 amps in this case). But I have lots and lots of cells, so I am almost never in a big hurry to get something charged. Incidentally, those 14500 and 16340 cells at maybe 750 to 1000 mAh, I use either 250 mA or 500 mA, depending on my mood…
Yes a lower charge rate is kinder to the cells and will help to maximize cycle life! It is a trade of, your patience for cycle life… 