18650's Care and Maintenance

[xdayv]

One bit of trouble is that if you're matching up cells, you'd need to check both internal resistance and capacity.
Most people just build packs from cells purchased together without added checks.

How to check for internal resistance?

 

[Budman231]

I wanted to share this video. It explains protected vs. unprotected 18650 cells. He does an excellent job explaining the dangers of over charge and over discharge whole showing how the protection circuit works.

https://www.youtube.com/watch?v=1rg3ZWxBNUE&t=31s

Bud

 

[jimbo231]

If I'm storing @ 3.7v and they drop below that over time. At what no load voltage should they drop to before I charge them back up to 3.7v? Also is that the proper thing to do... just charge to 3.7v? Will there be any negative effects by just bringing back up to 50 % capacity?

 

[david.allie]

The MC3000 is the most versatile advanced charger/analyzer out there IMO.

If you decide to buy one I will direct you to a distributor here in the US who will handle any warranty issues immediately and will give you an as good or better price than you can get on the China sites.

Torchmee, who in the US are you recommending for a purchase of the MC3000? I'd like to get one. TIA

 

[MarioJP]

Question. So this is my first set of 18650's and they're Panasonic 18650B, and after more than 2 years of use, i have noticed unsual heating on one or more cells during the constant voltage phase. Now i am not completely sure if the heat is coming from the charger and maybe losing my mind, but normally as the current begins to drop so does the temps. As the current gradually drops on all 4 cells the first 2 feels cooler but the third cell feels warm. But the last seems to be slowly heating up and does not seem to cool, and also the current drop on that cell drops much slower than the other 3. It's dropping but barely. Should i be concerned about this?

Thanks.

 

[fmc1]

Question. So this is my first set of 18650's and they're Panasonic 18650B, and after more than 2 years of use, i have noticed unsual heating on one or more cells during the constant voltage phase. Now i am not completely sure if the heat is coming from the charger and maybe losing my mind, but normally as the current begins to drop so does the temps. As the currently gradually drops on all 4 cells the first 2 feels cooler but the third cell feels warm. But the last seems to be slowly heating up and does not seem to cool, and also the current drop on that cell drops much slower than the other 3. It's dropping but barely. Should i be concerned about this?

Thanks.

How's the internal resistance?
Is the C. Current over 1.0A?
Let's start with the basics.

Frank

 

[MarioJP]

How's the internal resistance?
Is the C. Current over 1.0A?
Let's start with the basics.

Frank

1.5A charging
I'll check the resistance. I'll get back to you on that.

The cell in question has cooled and is about to terminate it is currently around 60ma

Charger: MC3000

 

[fmc1]

1.5A charging
I'll check the resistance. I'll get back to you on that.

The cell in question has cooled and is about to terminate it is currently around 60ma

Charger: MC3000

The MC3K checks the resistance at the start of a charge. It's the last line in SOV. You don't have to wait until the charge is finished.
If it's over 200 ml ohms you have you answer.

 

[MarioJP]

The MC3K checks the resistance at the start of a charge. It's the last line in SOV. You don't have to wait until the charge is finished.
If it's over 200 ml ohms you have you answer.

Cell IR
1: 76m
2: 74m
3: 77m
4: 78m (cell in question. Put tape to mark it)

So yea, i don't know what is going on. All i know during the constant voltage phase that cell was starting to get warmer while the other three was cooling down. They were all discharged and charged at the same time and with the same current.

Update

I know the charge going into the cell does not reflect the total capacity. But what happens when you have a cell that exceeds the rated capacity for Li-ion. After using these cells for more than 2 years, never seen the mAh exceed 3400 until now. I let the cells rest overnight and there seems to be no indication of problems after measuring the voltage the following day as it was at 4.19-4.18v. But the extra mah put into that cell raises questions. Is this part of normal wear and aging and losing it's eficiency or first sign of issues?

Just want to be assured that these cells won't go boom.

Thanks

 

[Dynapoints]

If you decide to buy one I will direct you to a distributor here in the US who will handle any warranty issues immediately and will give you an as good or better price than you can get on the China sites. $80 plus what ever the actual USPS shipping is from Ca. It will arrive in 2 to 5 days depending on where you live instead of the 3-4 weeks or more from China with basically no warranty. I got mine to my door for $85. He also sells the Opus if you decide to go that route.



Hi there!
I am new to the world of 18650 batteries. I have been reading up on explosions and fires and good chargers. Yesterday the big news story in Tampa was a vape the exploded started a fire that led to a fatality. Sober reminder i have to take care of this.
Please send me the info on the distributer of the mc3000 charger.

 

[klrman]

Is it harmful in any way to charge lithium batteries to around 90% such as 4.1V before using? I always feel better under charging them a little to keep the stress levels down, but I don't know for sure if I am doing the right thing.

 

[SilverFox]

Hello Klrman,

If you don't need the capacity your batteries will reward you by giving you improved cycle life. No problem at all.

Tom

 

[Gauss163]

It's beneficial - not harmful - to use shallower depth cycles. Further gains can be had by centering cycles around the half-full point (e.g. using 10% - 90% region) since this minimizes the time the cell spends at extreme voltages (where accelerated degradation occurs). See this post (and its links) for much further discussion (including charts and studies). I meant to update some of that info (and simplify it a bit) but - alas - a moderator locked the thread.

 

[klrman]

Hello Klrman,

If you don't need the capacity your batteries will reward you by giving you improved cycle life. No problem at all.

Tom

Hello SilverFox,

Thanks for the reply. Great, I was always hoping it was a good idea to do so, but it feels much better knowing for sure!

 

[klrman]

It's beneficial - not harmful - to use shallower depth cycles. Further gains can be had by centering cycles around the half-full point (e.g. using 10% - 90% region) since this minimizes the time the cell spends at extreme voltages (where accelerated degradation occurs). See this post (and its links) for much further discussion (including charts and studies). I meant to update some of that info (and simplify it a bit) but - alas - a moderator locked the thread.

Thanks for the info Gauss163, I going to read it all and try and absorb everything. I got my MC3000 recently and will make it work for me as much as possible.

 

[ktate749]

Am I correct in assuming, do not use the "Charge Test" on the Opus C3100 for a 18650 battery?

Thanks

 

[terjee]

Am I correct in assuming, do not use the "Charge Test" on the Opus C3100 for a 18650 battery?

Shouldn't be a problem.

It'll just do a charge, discharge, and charge again, giving you information about what capacity you got during discharge.

Also, see here: http://lygte-info.dk/review/Review Charger Opus BT-C3100 V2.1 UK.html

(Disclaimer: I don't currently own this charger)

 

[Gauss163]

Am I correct in assuming, do not use the "Charge Test" on the Opus C3100 for a 18650 battery?

Doing an occasional deep cycle to test capacity isn't going to cause much extra degradation to an optimally managed cell (as long as the capacity tests amount only to a small fraction of the number of equivalent full cycles)

 

[ktate749]

Looking at the data sheets for my Panasonic and Sanyo 18650 batteries, they have a value of 3.6V for the "Nominal Voltage". What are they referring to?

Thank
ktate749

 

[terjee]

Looking at the data sheets for my Panasonic and Sanyo 18650 batteries, they have a value of 3.6V for the "Nominal Voltage". What are they referring to?

The nominal voltage basically just means that's roughly the voltage they spend the most time at during discharge. You charge them to 4.2V, but it drops much more quickly down from there, than it does from 3.6V.

It's basically just the same as car batteries having a nominal voltage of 12V, yet you charge them to 13.6V or 14.4V, depending.