18650 basics

robkiller

New Member
I am new to building battery packs using 18650 cells.

i have a lot of these cells and have a few questions i am just not sure of the answer even with the document in from of me.
CGR18650CG
document https://drive.google.com/file/d/0B_pDil2dkRPTQWJtb05zaWI5emM/view

What is the completely charged voltage? i see nominal voltage as 3.6 but i also see in small print 4.2 v is this the voltage to charge it at or fully charged?
Whats the min voltage? I think its 3 as i see it says 3v cut off but not sure.

What should i set my max charging temp to be to keep things safe just in case?

Thanks everyone!
 

snoobler

Solar Honey Badger
This chemistry is the burny-explody type. Critical that you master it and understand what you're dealing with. Check youtube and watch lots of videos. Pay attention to the ones that caution you on the dangers of this chemistry and insist on the need for full cell testing and use of a BMS.

You tested each and every cell for capacity and IR, right?
 

gnubie

Photon Sorcerer
This clip has been posted a few times, but it's always worthwhile to post it again. Notice that the cells weren't even being charged / discharged when the gates of hell were opened. They can be damaged by inappropriate charging etc and then go foom some hours later.

 

robkiller

New Member
Yes i have been doing my research and i am going to test each and every cell for capacity and IR. I also will test for heat. I am asking this question because if i have any doubt about what i am doing or the info i have i am checking to make sure i understand it before i do anything. Any idea about the question at hand? Thanks for the warning.
 

snoobler

Solar Honey Badger
Not knowing those questions indicate you haven't done much research. The document you link clearly answers your questions.

I'm not trying to be an asshole (many would say it comes naturally), but that is not my intent. I would be happy to answer any questions about the data sheet that you find confusing, but if you look at the charts and try to understand them, you'll have all your answers.
 

robkiller

New Member
Well if i had not done my research then i would not have the document. Doing research and making sure you understand what you found are 2 different things. I am asking not because i dont have the info in front of me but (as we talked already this is dangerous) i want to fully understand and have no doubts. So if with the doc in front of me i new the answer i would not have asked. I am asking because even with the info in front of me i am not 100 percent sure of the answer.

Not being an asshole just want to find out the info so i dont do something wrong.
 

snoobler

Solar Honey Badger
I am new to building battery packs using 18650 cells.

i have a lot of these cells and have a few questions i am just not sure of the answer even with the document in from of me.
CGR18650CG
document https://drive.google.com/file/d/0B_pDil2dkRPTQWJtb05zaWI5emM/view

(1) What is the completely charged voltage? i see nominal voltage as 3.6 but i also see in small print 4.2 v is this the voltage to charge it at or fully charged?
(2) Whats the min voltage? I think its 3 as i see it says 3v cut off but not sure.

(3) What should i set my max charging temp to be to keep things safe just in case?

Thanks everyone!

Answer to (1):
1603065125895.png

1603065162387.png



Answer to (2) and (3);

1603065292642.png
 

RCinFLA

Solar Addict
You did not say how old they are but you can start by trashing any cells that measures less then 1.5v.

If less then 2.8v and greater then 1.5v you need to do a slow rate (100 mA charge) to get them above 3.0v before going to higher charge rate.

Beyond the above two items follow the charging spec rate, voltage, and time. You will need a balancer for series stacking use.

If you have enough quantity to justify it, suggest you buy a cheapo battery impedance tester to grade cells for matching There are a lot of Youtube videos on topic of recycled LiPo 18650 arrays. A large quantity array of LiPO's are not very safe. They can create a cascade of excitement.
 

robkiller

New Member
You did not say how old they are but you can start by trashing any cells that measures less then 1.5v.

If less then 2.8v and greater then 1.5v you need to do a slow rate (100 mA charge) to get them above 3.0v before going to higher charge rate.

Beyond the above two items follow the charging spec rate, voltage, and time. You will need a balancer for series stacking use.

If you have enough quantity to justify it, suggest you buy a cheapo battery impedance tester to grade cells for matching There are a lot of Youtube videos on topic of recycled LiPo 18650 arrays. A large quantity array of LiPO's are not very safe. They can create a cascade of excitement.
I do have a large number and i am testing them all. I also just got a megacell charger in and it is suppose to i say that with doubt but it says it can help me with watching the charging and look for bad batteries.
 

snoobler

Solar Honey Badger
You got it!

If you want to maximize cycle life, keep them between 3.5 and 4.05V. This will use 20-80% SoC pushing the cycle life into the thousands instead of only 500.
 

snoobler

Solar Honey Badger
Oh... and just because it gives you specs for 45°C, that doesn't mean it's a good idea for maximum life. 20-25°C is optimal. For testing or an occasional hot event, 45°C is fine. Just don't make a habit of it.
 
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