Battery cycle question

What exactly counts as a battery cycle? Does every recharinging count as a cycle, or only full recharge? If the battery was already partially charged at, say, 50%, and you recharge it, does it count as one more cycle?

 

I though a cycle was a full charge then discharge or vise versa.

 

Perhaps not, for if so, then if I never fully discharge, and always partial recharge, then it would always be 1 cycle even after hundreds of recharges

 

if you discharge 25% and then recharge the battery to 100%, if you do it 4 times, that's 1 cycle.

 

i think regardless of how many % you're at, as long as it charged (even for a second), it would be counted as 1 cycle. correct me if i'm wrong :\

 

Thanks! I also just found an article that says exactly the same as you say:

Myth 4: Don’t re-charge it too often, one time charged is one time less you can charge it. Ex: 100 “charge cycles” = can only charge for 100 times

Fact 4: Well, the actual math is a little different than what is written up there, and most of us have little idea of what charge cycle actually means. So, in plain, short English, one charge cycle means one full 100% charge, regardless of how many times you charge in between. Still confused? I am. Okay… here’s another example: let’s say you use only 20% per day and charge it, it will take you 5 days / 5 charges to consume one charge cycle, 5 x 20% = 100%. In the same light, if you use to 50% everytime and charge it to full, you will consume one charge cycle for every 2 times you charge it (Simple maths: 50% x 2 = 100%). However, regardless of the charge cycle, the capacity will still decline with the battery’s age. In that sense, older batteries will have less capacity even if it has never been charged before (Thanks to Hae Gunso for the information).

 

Personally, I take all battery claims with a very large grain of salt. Batteries do have lifespans and you can extend their performance through usage patterns, but until I see some data from a scientific perspective as to why a battery would behave in a given manner from an EE/physics perspective (or MythBusters does a bit on it ), I will be suspect of any claims made on how to extend battery life.

 

True. There are people who say they plug the battery in the laptop all the time even when using AC, and it still goes strong after a couple years. I guess we can simply use it any way we like within reasonable limit, recharge whenever necessary, just avoid going extreme.

I guess we can be convinced only when actually experiement two batteries during 5 years, but who's going to do that?

 

I'm one of those people. I also use the laptop's battery dry everytime because I hate AC. With battery life of 6.5 hours, I can get through a day with a single battery charge

 

Thanks for sharing your experience--actual experience beats theoretical speculations

 

But that isn't comparative. Just because running it down before recharging lasts doesn't prove that a different pattern does not.

 

or that the other pattern isn't superior. The only way is to do a controled experiment with similar batteries, and repeated at least once more for consistancy...someone TEST THIS!!!

 

OK, there are MANY variables that go into how long your battery lasts but nearly ALL laptop batteries are Lithium Ion with Cobalt Oxide cathodes. Here are the factors that effect their life.

1. DoD, Depth of Discharge, the deeper you discharge the battery the shorter it's cycle life (cycle life is defined as being over when the battery only holds 80% of it's original capacity) discharging to ~40% is optimal. Conversely charging the battery to 100% also shortens the life, most laptop bats are actually at 90% when they show 100% and stop charging.

2. C rate. A 10 amp hour battery producing 10 amps is discharging at 1C. A 10 ah battery producing 20a is discharging at 2C. Anything above 1C starts to decrease the cycle life of the battery (though not all chemistries are like this, this figure is for li-ion with cobalt oxide cathode)

3. Temperature, higher temperatures increase the amount of energy available for a given charge (to a point) but decrease the cells cycle life, temps over 40deg C have an exponentially increasing (with T) negative affect on cycle life. Also if temps are below or near freezing you lose cycle life and the energy available per charge is decreased. THE EFFECTS OF #2 AND #3 ARE MULTIPLIED, A HIGH C RATE AT HIGH TEMP IS THE WORST.

4. There are many other smaller factors specific to exact chemistries I have heard rumors that it is good to vary the DoD. Simply leaving the battery in a really hot place (car in the sun) or operating a laptop with poor cooling that heats up a lot will decrease the batteries life even when it is not in use.

 

Beautiful. +Rep for that, deputc. Finally someone with more than a gut feel or hearsay/rumor on this subject.

 

No problem, batteries have been an area of personal interest to me for the last four and half years as I believe that they are destined to become the primary means of energy storage for all applications save freight and aviation.

 

Haven't people already designed high capacity capacitor to replace those batteries? Much safer, higher capacity, high discharge rate..etc
Those 18650s in laptop batteries suck pretty bad. The ones in my acer aspire one is rated at 1600mah. I could even get 2400mah protected cells for like $2 each.