Battery sense or not?

[ltrainer]

Please correct me if my information is wrong. I am far from being a battery wizzard.

Lithium batteries have a shelf life of 2-3 years from manufacture. This happens even if you dont use your batteries very often. THey will just die of old age.

They can be charged 300-500 times. If a lithium battery is half charged and you charge it that counts as 1/2 charge. If its 1/4 discharged and you charge that counts as 1/4 charge. SO a half discharged battery should be able to be charged 600-1000 times.

Buying a huge amount of batteries would be counter productive because they will die of old age way before they have been charged too much.

Based on this I have 3 batteries (aw imr 18650s). If I changed them around 3.8 volts I should get at least a couple of years based on recharge rates. More probable they will die of old age, not charge cycles. Having three, if one dies or is lost I have two which easily keeps up with my vaping until I can get a replacement.

What say you?

 

[six]

Li-on batts can last a decade if stored properly. 40% charge and in the freezer.

Li-on batts - There is no way of knowing how many charge cycles they will live through but most of the manufacturers have hugely inflated claims such as the 3-400 you've read somewhere.

I've read conflicting information from different manufacturers weather or not a partial discharge and recharge counts as less than a charge cycle. I've also read conflicting information regarding the chemistry itself. From what I've read on candlepower and elsewhere, I think I'd lean toward the belief that anything under a 15% discharge and recharge might be easy on the electrolyte. But beyond that, you may as well have drained to 3.5v. -- YMMV on that. I'm really going by who I tended to trust while reading rather than having as much knowledge as who wrote what I was reading.

 

[TennDave]

We Need Techno in this thread- he knows a ton about batteries!

 

[Decidion]

Here are a couple of links to useful information at batteryuniversity.com:

Basics of discharging:
Battery Discharge Methods

How to Charge/When to Charge:
Frequetly Asked Questions on How to Charge Batteries

I think the bottom line is that you will never know for sure exactly how many cycles your batteries will last. It is truly a matter of many factors (ie actual use, production differences, storage time, temperature during use, charging and storage, etc.)

But the common conclusion (and this is in general for most, if not all rechargeable batteries) is that discharging a battery very low (or fully) can *greatly* shorten it's life or destroy it. Conversely, the less the battery is discharged before recharging it the greater the life expectancy you can get out of it.

Here is a link to a page that has a battery life/cycles calculator. I am not exactly sure of all the variables, but but is easy to experiment around just altering the Depth of Discharge number (a percentage):

Manganese Lithium Rechargeable Cell Lifetime Calculator - Maxim

For example, at 10% DOD (depth of discharge), you will get 300 cycles. For discussion sake, lets say a 10% discharge is equivalent to 1 amp of battery power.

At 20% DOD, you get 130 cycles. If 10% = 1 amp, and 20% = 2 amps then we have:

300 cycles of 1 amp = 300 amps of output from the battery during it's life

130 cycles of 2 amps = 260 amps of output from the battery during it's life

I cannot say if this curve you could plot if you extrapolate this is linear, but check out the chart at the bottom of the page in the last link... the number of cycles drops off dramatically with higher DOD's.

I guess the real question is if AW is rating their 18650 IMRs at 500 cycles, what is the DOD they use to calculate that life span for their battery?