battery storage questions

[mach1ne]

as my collection of devices grows, so does my collection of batteries, and the length of time it takes to cycle them out and recharge them (compared to only having one mod and two sets of batteries alternating daily). i remember reading in a battery faq that you are supposed to store your batteries at a certain voltage (cant recall the exact number, but it definitely wasnt 100% charged)...

so im wondering what length of time is considered 'storage' compared to 'waiting to be used', what the exact storage voltage is, if that differs depending on the battery (all 18650s), and whats the best way to get them to proper storage voltage. i have a nitecore charger but i dont think it has a discharge feature...thanks for any help.

also, bonus question: how long will well cared for 18650s last me? im scared that i wont be able to replace some of these in a few years (i have a bunch of vtc4s for example).

 

[Neunerball]

as my collection of devices grows, so does my collection of batteries, and the length of time it takes to cycle them out and recharge them (compared to only having one mod and two sets of batteries alternating daily). i remember reading in a battery faq that you are supposed to store your batteries at a certain voltage (cant recall the exact number, but it definitely wasnt 100% charged)...

so im wondering what length of time is considered 'storage' compared to 'waiting to be used', what the exact storage voltage is, if that differs depending on the battery (all 18650s), and whats the best way to get them to proper storage voltage. i have a nitecore charger but i dont think it has a discharge feature...thanks for any help.

also, bonus question: how long will well cared for 18650s last me? im scared that i wont be able to replace some of these in a few years (i have a bunch of vtc4s for example).

I'm unaware of having to store 18650 batteries at a certain percentage. However, if it comes to LiPo packs, most commonly used in DNA200 mods, it's a different story. As a R/C Collective Pitch Helicopter "pilot", I know, if you need to store those LiPo packs for 2-3 months (usually during winter times), you want to store them at 50% charge. If it's longer than 3 months, you want to fully charge them and discharge to storage charge, in order to avoid damage to the cells.
I don't see, where you would store 18650 batteries that long. However, they will discharge as well over time, so you want to make sure you don't let them sit and go below the threshold.

 

[vap3r]

They can be stored in a fully charged state @ 20 to 25°C for 30 days at which time capacity should be ≥ 90% of nominal capacity. The longer you plan to store them, the lower the tempurature at which they should be stored in an effort to reduce the inevitable loss of capacity and increase in internal resistance. Typical specifications for storage of up to one year dictate an environment between -20 to 20°C at approximately 40% of a full charge.

 

[vap3r]

how long will well cared for 18650s last me? im scared that i wont be able to replace some of these...

That is impossible to answer. Cell manufacturers seem to have settled on 70% of nominal capacity as the limit on useful cycle life. Suffice to say that if you use your cells in regulated devices, they will obtain more useful life than in mechanicals as the cell will still be able to provide power at your accustomed levels, albeit at a shorter duration than expected. 70% of nominal capacity on a mechanical coupled with a concomittant rise in internal resistance would result in both short usage and a noticeable drop in voltage per draw. How to test for capacity? Bay chargers such as the Opus BT-C3100 and the SkyRC MC3000 offer charge-discharge-charge cycles to measure mAh in/out. Most hobby chargers and dedicated battery analyzers also offer the means to determine capacity. Offhand, battery technology is always moving forward. The next great cell is always around the corner. I see no reason to concern yourself with availability.

 

[mach1ne]

thanks guys

 

[dr_rox]

FYI
Just wanted to clear up the 70% to 90% and quantify it with a measureable value.
Most of the R/C chargers have a storage setting. They will discharge a battery to 3.7 volts ans shut down.
Fresh, new 18650's that I have received, voltage has always ben around 3.6/3.7 v.

 

[suprtrkr]

A good storage voltage is 50-70% of full charge, but it isn't necessary unless you're planning to store them longer than a month, with lower charge and lower storage temp the longer you want to hold them. You can always take them out of the charger at half charge, you know It would also be possible to maze up some LEDs or something to use to discharge them if you're worried. The VTC4s may go south-- I'm a big fan too-- but they've been saying that for years and it hasn't happened yet. Not to worry; it now looks like LG is building us a solid replacement in the LG HD2C, which is a 25A battery with, if memory serves, better storage capacity than the VTC4.

 

[vap3r]

Most of the R/C chargers have a storage setting.

IMHO, a hobby charger or similar is a must-have tool for any self-proclaimed battery junkie. I often recommend R/C chargers as either a primary or secondary charging device to both novice and experienced vapers alike. By charging on a granite block acting as a heatsink, cell surface temps never rise above 39°C (starting temp of 23°C) even when charging at a rate of 1C. This is a remarkably low charging temperature which only serves to increase cell lifespan.

 

[Jon@LiionWholesale]

3.6-3.7V is the optimum storage voltage. 3.5 or 3.8 is fine too. I'd start thinking about setting them to storage voltage if it's going to be longer than a few weeks.

The Opus BT-3100C can set them to storage voltage if you cut out a hole to access the internal switch (or in our case we have multiple of them and always have some set to storage voltage and some set to full voltage).