Can singles be married?

[izen]

Have two individual Samsung 25R's (blue wrap) - bought together - and used one after another in a single 18650 mod. Each is backup to the other. They've been in use about six weeks. Their discharge and recharge rates (patterns?) have been very similar but not exact.

Can I marry these two (blue) now? Start using them as a married pair in a dual 18650 series mod? - a sigelei 100W Plus - if that makes a difference.

I would guess yes, but am uncertain. Don't have a lot of experience in this area. Also have fresh, new, unused pair of green wrap 25R's that are charging up now, but I'd like to use the blue wrap pair as an alternate/backup pair for them. Advice is appreciated. Thanks.

Rob

 

[TrueNorthist]

The blue wraps have a lower cycle rating than the green, but very similar discharge rates if I recall correctly, so off the top of my head (a very dangerous place to be) I would say they are an adequate breeding pair. But the genuinely smart guys should pipe in at some point and give you the inside dope.

 

[izen]

Clarified first post... New green wrapped 25R's are a pair (married from day 1)... Can I marry the two prior individually used - blue wrapped - 25R's? (as backup/alternate pair)... that's the question, but I think I'm going to do it anyway.

 

[TrueNorthist]

Clarified first post... New green wrapped 25R's are a pair (married from day 1)... Can I marry the two prior individually used - blue wrapped - 25R's? (as backup/alternate pair)... that's the question, but I think I'm going to do it anyway.

I tend to avoid doing that, but I have grouped fairly new used batteries after running tests to ensure they are within .02 volts of each other, both at rest and especially under a load. It is always best to use new cells that "grow up" together in the same device, but I have done it with only minor lacerations and a ringing headache the next morning. I would also exercise a lot of caution if the cells are well used. >100 cycles or so would give me great pause and I'd likely reconsider.

I also suggest you wait for one of the more experienced battery folks to pass judgement, as my credibility is zip in court.

 

[izen]

They've both been used as singles in the same device (eVic VTC mini), and no other. I'd guesstimate about one month's time on them, each cycled about twice daily. The discharge & recharge of each has been very similar, but not exact. That's the best I can volunteer. I've little experience with this; so my uncertainty, but I've just gotten my first dual battery device and the new (green) pair are being charged-up for the 1st time. These older blue wrapped singles were both ready & waiting @ 100% so I threw 'em in. Been in use now for about 5 hrs., and now down 35% (65% remaining) in the Sigelei. Seems Ok to me. What could go wrong here, if anything BTW, thanks for your comments. They're appreciated.

 

[TrueNorthist]

They've both been used as singles in the same device (eVic VTC mini), and no other. I'd guesstimate about one month's time on them, each cycled about twice daily. The discharge & recharge of each has been very similar, but not exact. That's the best I can volunteer. I've little experience with this; so my uncertainty, but I've just gotten my first dual battery device and the new (green) pair are being charged-up for the 1st time. These older blue wrapped singles were both ready & waiting @ 100% so I threw 'em in. Been in use now for about 5 hrs., and now down 35% (65% remaining) in the Sigelei. Seems Ok to me. What could go wrong here, if anything BTW, thanks for your comments. They're appreciated.

My habit — that I am convinced has saved me wearing out batteries quickly — is to recharge when they hit 75% max, no matter what. My EV specialist told me some time ago it is even better to keep them as charged as possible which greatly increases their longevity and he was right, as usual. Since 2012 I have tossed only 3 cells due to their weakened performance on my tester. (Several others have been heaved for reasons owing to their faulty nature, but I digress...) My nick in the shop is Pancho Villa because I have special cell-pockets sewn to my coveralls. The batteries look like bullets in a bandoleer under my arm.

"Batteries? I don't need no stinking batteries!"

edit: again I suggest you look into this subject further as I am just an no-talent loser with zero prospects. I coulda been a contender. I coulda been somebody, instead of a bum, which is what I am, let's face it...

 

[sofarsogood]

I have a Cuboid two cell mod on order. I was reading joytech's page on the mod and they recommend the batteries should be within 0.3 volts. That might be a generic recomendation and apply to other dual cell mods.

 

[rallykid]

Honestly for the price of batteries I would spend the $16 just for peace of mind. They may work fine as a married pair but I personally am not willing to risk a battery venting in something I hold pointed at my face to save a few bucks.

I have several batteries that have been through an almost religiously identical charge cycle and I still won't use them as a pair in my 3li or as triples in my Reuleaux.

For me it comes from working in the cellular industry for almost 20 years and racing RC cars, flying RC planes and Helis for 30 years. I have witnessed what a battery is capable of and personally, I would rather blow $20 to get new pairs/sets which is exactly what I did when I went from a single to a dual and what I did again when I went from pairs to triples.

 

[izen]

@ rallykid - I appreciate the good advice. I guess one can never be too safe. What might cause them to vent?

Isn't my degree of risk greatly mitigated by their similar history; purchased together but used as singles, (similar discharge & recharge cycles), that they're quality batteries to begin with... that I never build too low, never deeply discharge (always above 25% remaining if not more), and that they going to be used in a quality regulated device (Sigelei/yihi chip)? ...If they were going to be used in an unregulated mech mod, I wouldn't have even asked these questions to begin with.

Sorry to come-off as argumentative... Really just highly curious and trying to be logical - although I am short on cold hard facts & knowledge in this arena. - Thanks for the advice !!!

 

[AzPlumber]

From the moment you start cycling batteries they slowly start to degrade. This means the internal resistance starts to increase. This internal resistance effects the batteries ability to freely migrate lithium ions within the cell during charge or discharge.

When batteries with different internal resistance are used together and unable to discharge at the same rate one ends up taking the brunt of the load. The greater the disparity between batteries the more likely something bad can happen.

The purpose of marrying and rotating (each cycle) brand new batteries is they are both kept in the same environment and will have similar internal resistances. Used as single batteries, even in the same device, there is no way the guaranty the same rate of degradation.

 

[coilburner]

@ rallykid - I appreciate the good advice. I guess one can never be too safe. What might cause them to vent?

Isn't my degree of risk greatly mitigated by their similar history; purchased together but used as singles, (similar discharge & recharge cycles), that they're quality batteries to begin with... that I never build too low, never deeply discharge (always above 25% remaining if not more), and that they going to be used in a quality regulated device (Sigelei/yihi chip)? ...If they were going to be used in an unregulated mech mod, I wouldn't have even asked these questions to begin with.

Sorry to come-off as argumentative... Really just highly curious and trying to be logical - although I am short on cold hard facts & knowledge in this arena. - Thanks for the advice !!!

What might cause them to vent? Perhaps doing exactly what proposed.

 

[izen]

What might cause them to vent? Perhaps doing exactly what proposed.

Yes, and perhaps they won't... Hey it was a fair question. All were fair questions, and reasonable scenarios that a battery newb might assume could be workable. At least AzPlumber provided some explanations... (ya know buddy)... I'm a relatively cautious but curious guy. We live in a world where we're constantly bombarded with sh%t that we should be afraid of... I'm dismissive of a lot of that nonsense, and when I'm curious and (even mildly) concerned. I ask questions., and then take precautions if need be. Many folks don't ask questions they just accept what they're told. I'm aware the batteries need to be married from the jump. One pair is, I simply questioned the possibilities for the other. Nothing wrong with that my friend.

 

[coilburner]

Yes, and perhaps they won't... Hey it was a fair question. All were fair questions, and reasonable scenarios that a battery newb might assume could be workable. At least AzPlumber provided some explanations... (ya know buddy)... I'm a relatively cautious but curious guy. We live in a world where we're constantly bombarded with sh%t that we should be afraid of... I'm dismissive of a lot of that nonsense, and when I'm curious and (even mildly) concerned. I ask questions., and then take precautions if need be. Many folks don't ask questions they just accept what they're told. I'm aware the batteries need to be married from the jump. One pair is, I simply questioned the possibilities for the other. Nothing wrong with that my friend.

No theres nothing wrong with that and I wasn't trying to be an .... I was just letting you know that un married batteries could vent.

 

[BobC]

No theres nothing wrong with that and I wasn't trying to be an .... I was just letting you know that un married batteries could vent.

Why?
What is the science to back up your statement?
If you marry two same equally used singles, you should have no more of a problem then marrying two brand new batteries

 

[izen]

edit: again I suggest you look into this subject further as I am just an no-talent loser with zero prospects. I coulda been a contender. I coulda been somebody, instead of a bum, which is what I am, let's face it...

Just noticed. Funny! I appreciate the help and advice, (from one bum to another).

 

[coilburner]

Why?
What is the science to back up your statement?
If you marry two same equally used singles, you should have no more of a problem then marrying two brand new batteries

If you use a set of batteries that aren't the same age and used the same the weaker battery will take the brunt of what's being asked of your batteries.
As far as the last thing you mentioned, I suppose there wouldn't be a problem if they are the same exact age and got discharge and charged the same amount each time they were used. there might not be a problem, at least for a while, even if they weren't but I would want to find out. Battery safety is the single most thing you should take seriously when vaping and that's not something Im willing to gamble on.

 

[AzPlumber]

Why?
What is the science to back up your statement?
If you marry two same equally used singles, you should have no more of a problem then marrying two brand new batteries

and you have the "science" to back yours?

 

[BobC]

If you use a set of batteries that aren't the same age and used the same the weaker battery will take the brunt of what's being asked of your batteries.
As far as the last thing you mentioned, I suppose there wouldn't be a problem if they are the same exact age and got discharge and charged the same amount each time they were used. there might not be a problem, at least for a while, even if they weren't but I would want to find out. Battery safety is the single most thing you should take seriously when vaping and that's not something Im willing to gamble on.

Huh?
Why just for a while?
You do know no two batteries are identical, even brand spankin new, so close in age and use is good

 

[BobC]

and you have the "science" to back yours?

Yes, as no two batteries, even from the same manufacturer, are identical in capacity when new, lightly used batteries of similar age should be just as compatible as two new ones.

Secondly, more has to do with the amount of stress put on the battery pack

 

[coilburner]

Huh?
Why just for a while?
You do know no two batteries are identical, even brand spankin new, so close in age and use is good

I said " there might not be a problem, at least for a while" because if the problem doesn't show up immediately it will most likely get worse over time as the weaker battery is taking more and more of the load.
As far as the last thing you said, whatever. its your face and house at risk. your right, no two batteries are identical but being close in age and use isn't something I would call "good". When it comes to batteries I don't think you can be safe enough. If you want to cut corners I sure as hell hope your prepared for the possible consequences.