Battery Load Cycles

Actuallly what you are doing is the worst possible way to treat a battery and will likely kill it within a few months if you go on.

Even with li-ion (which is SUPPOSED to be memory free) it is ALWAYS best to fully discharge a battery before recharging it. And in order to maintain a battery in peak condition YOU MUST fully discharge it AT LEAST once a month.

All batteries are subject to the laws of physics which dictates that if you have a reversible process (as in charging & discharging) then it will exhibit some degree of hysteresis... that is every time you repeat the cycle there will be a small loss in capacity. The only way to minimise this is to FORCE the cycle to its end point before travelling up the reverse curve. That way you change direction (ie from discharge to charge etc) when the battery is empty and this reduces the capacity loss VERY considerably.

Li-ion batteries are much better than Ni-MH or Ni-Cd but over time even they will fail. Mind you if you look after them, properly you can make them last for 4 or 5 years as I have proved with my previous ibook G3.

As you say leaving it plugged into the mains is ok providing you fully discharge once a month... which you will find is official Apple advice... can't find it now, but its on the website somewhere under "care of your battery"

take a look at this:

http://www.apple.com/batteries/notebooks.html

The rule of thumb I've always heard is that a load cycle is triggered at ~5% discharge.

In other words, if you unplug your computer and run it down to 98% and then plug it back in, you shouldn't see the load cycle count increment, but if you unplug it and run it down to 93% and then plug it back in and charge it, you will see it increment.

I haven't actually confirmed this with any kind of experimentation, but that's probably not a bad rule of thumb to follow.

Even with li-ion (which is SUPPOSED to be memory free) it is ALWAYS best to fully discharge a battery before recharging it.

Actually jennyd this is not true. Not only that it is recommended that with Li based batteries (in this case Li-polymer) one should try not to fully discharge unless you are calibrating it. Going down to around 30% is the easiest on your battery.

And in order to maintain a battery in peak condition YOU MUST fully discharge it AT LEAST once a month.

Again not true. The wording is AT MOST as opposed to AT LEAST. For optimal performance a recommended calibration period is between every 4 to 8 weeks. Calibrating more often than every 4 week can actually reduce battery performance.

Generally speaking though, to maximize the performance and time you get that performance you should aim to accrue around 300 charge cycles at around 2 to 3 years which translates to averaging about 2-3 charge cycles per week. Personally I run my MBP on battery for about an hour a day.

Well that explains all my load cycle increments then.

Actually it doesn't give his charge cycle description is not correct. One charge cycle is considered to be one full discharge of the battery along with it's full corresponding charge. However, this full cycle does not need to complete in one stage.

So, by fully discharging it and then fully charging it is one cycle.

Additionally, discharging it by 50%, then charging 20%, then discharging 10%, then charging 30%, then discharging 40% and finally charging 50% is also one charge cycle. Note that the total charging is 100% and the total discharging is also 100%.

Therefore, your cycle count of 10 is equivalent to (and not limited to) discharging your battery fully 10 times and charging it fully 10 times. Over 10 days I doubt you would have missed that. More than likely your battery did not come with a cycle count of one. I doubt you checked it when you first turned on your MBP.

You do seem to going through charge cycles rather quickly. I'd monitor your battery usage (count percentage points and not time) and see if it correlates at all to how fast you're going through cycles. If nothing matches I'd think about calling AppleCare.

Quote : johannes.egger

take a look at this:

http://www.apple.com/batteries/notebooks.html

Well it would seem as though I was right then as if you follow that link the words are as I originally stated "AT LEAST" and NOT as the person who corrected me said "AT MOST"... /End Quote.

In the final event I am only a physicist turned IT engineer and I am not a battery expert so i have to rely on what apple tells me.

Be very careful with the wording that's been used. The Apple battery page Johannes, and then you, references states…

"Apple recommends charging and discharging its battery at least once per month"

The thing is, what you wrote was…

"YOU MUST fully discharge it AT LEAST once a month"

While it appears the same it is not. Fully discharging the battery is a calibration. If you then read Apple's calibration page it states…

"you should perform this procedure when you first use your computer and then every few months thereafter"

Yes it's semantics although the difference, while subtle is very important.

PS Apple should have been clearer in their wording.

Thanks Ned ... so you're saying that when Apple says:
"Apple recommends charging and discharging its battery at least once per month" That doesn't mean "calibrate", it just means what it says.

Calibration is a whole other process, which according to Apple should be done every few months or so after initial start-up.

Thanks for the clarification.