When do you Replace Batteries?

[MaxximusRevelation]

So last year I bought 10 18650's that I have been using. I generally use around 3 batteries a day, charge the used ones, and put them back into the que to be used after all the others have been used. So for the ten batteries on average every week are being used and charged .7 times a week. I had plans on replacing all 10 batteries after the year mark.. Well the year mark is coming around and I ended up purchasing 15 new batteries but the question I had was, how often do people replace their batteries? All my old batteries still hold charges and vape fine, I have 20amp, 25amp, and 30amp batteries that are never used or pulsed in their continues ratings. So if I had a 25amp build I would always use 30amp batteries so as not to damage them. I have never drained a single battery below 3.7v and will sometimes charge them when they still read between 3.8-3.9v

Is there a way to test if the batteries still perform like new? Such as charging it and checking its voltage after a certain amount of weeks or something? Or using it with a known ohm and amperage and tracking down how many puffs I have? Or should I just not worry about it and throw them out and start using my new ones? I would rather be safe than sorry and the cost of throwing away batteries every year is worth not having a catastrophic failure but I would like to know others opinions on how often they replace their 18650's.

The batteries I use are: LGHE4, LGHD4, and LGHG2, and LGHB6 so no re-wrapped brands.

 

[dennism]

I replace mine when they won't take a full charge.

 

[MaxximusRevelation]

I replace mine when they won't take a full charge.

So you use them until they can no longer charge up to 4.2V? If I used a regulated device there might be a slim chance I would do that but 3/4 of my mods are mechs and I wouldn't feel safe using them until they couldn't function right.

 

[sonicbomb]

There are no hard and fast rules. General advise is one year or 300 charge cycles, but there are multiple factors that can affect their longevity so this is just a guide. The problem is unless a cell blatantly isn't holding a charge it's performance is hard to gauge. The main issue for me is that as the cell ages it's CDR will drop which causes me concern as I push my cells quite hard.
I go with a "if in doubt replace" methodology when it comes to batteries.

 

[Train2]

I noticed that after ROUGHLY a year of similar use (rotating em so they're idle a bit between use) that an older one will start charging only to 4.19 then 4.18, etc. That's when I think about getting new ones.

I haven't DUMPED the old ones, but they kind of move to "backup"...I've only actually gotten rid of those that were like 3 years old, and worse specs to begin with.

 

[MaxximusRevelation]

Thanks everyone for their replies and input! I'm gonna play it safe and use the old batteries as back ups or for builds requiring far less than their continues amperage, they should be fine though as they have less than 100 charges but five dollars a battery isn't really an argumentative topic when regarding safety haha. To bad they don't have chargers yet that tell you if the batteries aren't performing up to par.

 

[Barkuti]

BU-808: How to Prolong Lithium-based Batteries @ Battery University

According to the article, in order to remove all voltage related stresses from 4.2V charging voltage li-ion cells a maximum voltage of 3.92V/cell should not be surpassed. This means you'll be limited to about ≈60% of the maximum cell energy, although this varies with cell chemistry and I've noticed most modern cells hold at least ⅔ of the capacity/energy at that point. 3.92/4.2 is tantamount to 14/15, this fraction is to be applied to know the equivalent numbers for higher max voltage cells (4.3/4.35V).
In the article it is claimed that each 0.1V reduction in peak charge voltage doubles the cycle life. At a sustained max of 3.92V/cell, we're speaking of about 8x the amount of cycles and at least 4x cell lifespan.
In my experience, I can more or less comfirm those claims.
For my liking, you keep your cells overvolted, suffering undue stress. But this is just my humble opinion…

Cheers

 

[MaxximusRevelation]

Definitely an awesome read there, thanks! I would have to carry a backpack with me if I were to have HB6's only charged to 3.9V though

 

[herb]

I always put them on the charger well before they are fully depleted and no issues so far , some are two years old and still work great .

 

[Rule62]

I keep using them, as long as they still charge up to 4.19 or 4.20. I only use mechanical squonkers; no regulated mods. I have discharged them down as low as 3.48 or 3.5, and they still charge up fine. I slow charge everything, usually at .25 or .5 amps.

 

[VapieDan]

If they act funny
Time to spend some money!

 

[Barkuti]

A little calculations for me to extend on the aforementioned with regards to available cell energy based on its voltage. The latest fish in the pond as subject: the Samsung INR21700-30T.

I am going to link to HKJ's graph because he does low rate discharge, making my life much easier to estimate the interval points of the definite V × I output energy integral. He also uses 4 terminal battery holders, allowing him to accurately measure battery voltage (right at its terminals); haven't asked Mooch, but due to a slight difference (drop) in his battery voltage graph I believe he may not be measuring voltage right at the terminals. Take a look:

There are slight differences, probably caused because of the further voltage drop in whatever it is between the battery terminals and the voltage probes in Mooch's setup. The drop increases with current, you'll hardly see it between the 10A curves, but it's easy to spot on the 30/40A ones (≈80mV at the ≈625mAh point at 40A, equivalent to a voltage probe path resistance of about 2mΩ). HKJ, however, needs sturdier battery holders (meltdown at 50A LoL!).

0K. Let's go with the figures. Let's say the “3.92V no load” point is at ≈900mAh, thus this is the unused capacity at this “alleviate all voltage related stresses” value for this cell. Another relevant point is at ≈2900mAh, which I'd call end of discharge curve slope shift.
Please note this is just an estimation, so I'll average the voltage value in each section.
Discharging at 30A with the INR21700-30T (voltages estimated by rule of thumb weighted average):

• ≈3.660V × 0.90Ah = 3.29400Wh for the first section (4.2 down to 3.92 no-load volts).
• ≈3.230V × 2.00Ah = 6.46000Wh between the 0.9 and 2.9Ah points.
• ≈2.865V × 0.05Ah = 0.14325Wh at the very end.

Total energy output at 30A down to 2.8V:
ET30 = 3.294 + 6.46 + 0.14325 = 9.89725Wh

Total energy output at 30A charging up to 3.92V (max lifespan approach):
EC30 = 6.60325Wh

Estimated percentage of available energy at 3.92V max vs 4.2V max: 66.718027735%

Above 66.7% at 30A with this cell. Wow!

Looks good.
Hope you like this dissertation.

Cheers

Edited on April 19th, 2017, 0:15; a couple fixups.

 

[Rossum]

So you use them until they can no longer charge up to 4.2V? If I used a regulated device there might be a slim chance I would do that but 3/4 of my mods are mechs and I wouldn't feel safe using them until they couldn't function right.

I have yet to see a cell that won't charge up to 4.2V.

I think the question is what happens after the charger gets it to 4.2V, holds it there until the current drops to the charger's cut-off, and then stops charging. Older cells appear to self-discharge from 4.2V more quickly than newer ones, and the effect also seems to vary by brand and type of cell.

 

[DaveP]

If it still provides the vape time I'm used to I continue to use it. If your mod has a resettable puff counter that would be a good indicator for comparison as long as you use the mod's cutoff for the vape time comparison.

I have some old button top AW's that I occasionally use in my old Provari V2. I bought those in 2011 and they still provide good vape time. I have double and triple married sets I use dedicated in certain mods. Then, there's the single batteries I use in my Pico and other mods.

 

[Rossum]

If your mod has a resettable puff counter that would be a good indicator for comparison

Meh. The mechanical mods I use don't have puff counters. I always refill my mod's juice bottle when I put in a new battery. I judge battery capacity by how much of the 8ml of juice I can vape before I want a fresh battery. It definitely declines as batteries age, but some batteries age more gracefully than others.

I've never understood why regulated mods don't track how many mAh they've pulled from a battery.

 

[DaveP]

Meh. The mechanical mods I use don't have puff counters. I always refill my mod's juice bottle when I put in a new battery. I judge battery capacity by how much of the 8ml of juice I can vape before I want a fresh battery. It definitely declines as batteries age, but some batteries age more gracefully than others.

I've never understood why regulated mods don't track how many mAh they've pulled from a battery.

I'm so used to electronic mods I sometimes forget that mechs don't have electronic data gadgets!

Lack of MAH totals is probably due to the complexity of different coils over time and storing the info when it changes. Puff count, puff length, resistance of a particular atomizer, and storing the data would add complexity. It's easy to increment a simple puff counter, though.

 

[Rossum]

Lack of MAH totals is probably due to the complexity of different coils over time and storing the info when it changes. Puff count, puff length, resistance of a particular atomizer, and storing the data would add complexity. It's easy to increment a simple puff counter, though.

It's a regulated mod. It knows how much power it's applying to whatever coils you have on there and for how long...

 

[DaveP]

It's a regulated mod. It knows how much power it's applying to whatever coils you have on there and for how long...

True, but battery change indicators are based on present voltage. Simple and reliable, but cutoff voltages vary with the mod. You'd think that there'd be a way for mods to indicate MAH from the information it gets from the battery.

I rely on the MAH rating from my Xtar VC4 charger for battery condition. Even that changes with present voltage when it's placed on the charger and the amount of charge required to reach 4.2v.