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battery charge does not go to 100%

bki122689

bki122689

macrumors 6502
Original poster
Sep 18, 2008
387
0
hey guys,

So I've only had my macbook pro for 2 months and the battery would charge up to 100%. It would stop at 98%. On Istat it says the health is 99%. Is my lithium battery already starting to go bad? What do you think is the cause of this.

Thanks
 
No, it's not going bad. The battery health and charge indicators will vary from time to time, up and down. It's not a big deal.
 
the battery trickle charges (goes down then up) so the battery doest sit on 100% the whole time when fully charged and plugged in. discharge it to below 90% then back to full and it should say 100%.
 
Yea, it scared the crap outta me when I saw the mAh was 4800 when like an hour before it was 5208. It goes up and down. Just let it drain all the way below 95% and recharge. It will go back up to 100%. And unless the battery goes below 50%, it does not count as a cycle. Although it's best to calibrate the battery every few months or so (no need for twice a month) to even it out. To calibrate, just let it drain until it shuts down. Then recharge back to 100%.
 
gusious said:
Always calibrate. As many times you can. This will keep your battery very very healthy.;)
Click to expand...
Once a month is all that's necessary.... and it's all that Apple recommends. Not even that is necessary if you frequently run on battery, so you're going through cycles anyway.
 
what do mean by cycles? is one considered if it goes below 50?

and reseting it just drain it all the way down until it shuts down right?
 
Samarium said:
You should calibrate your battery about 2 times a month.
Click to expand...
gusious said:
Always calibrate. As many times you can. This will keep your battery very very healthy.
Click to expand...
Sorry but that is dreadful advice. LiIon batteries do not like to be deep discharged with such regularity. Nor do they like to left on permanent charge while the laptop is in use - it causes heating of the battery which can also shorten its overall life.

A lithium-ion battery provides 300-500 discharge/charge cycles. The battery prefers a partial rather than a full discharge. Frequent full discharges should be avoided when possible. Instead, charge the battery more often or use a larger battery. There is no concern of memory when applying unscheduled charges.

Although lithium-ion is memory-free in terms of performance deterioration, batteries with fuel gauges exhibit what engineers refer to as "digital memory". Here is the reason: Short discharges with subsequent recharges do not provide the periodic calibration needed to synchronize the fuel gauge with the battery's state-of-charge. A deliberate full discharge and recharge every 30 charges corrects this problem. Letting the battery run down to the cut-off point in the equipment will do this. If ignored, the fuel gauge will become increasingly less accurate. (Read more in 'Choosing the right battery for portable computing', Part Two.)
Click to expand...

There is so much misinformation about battery care - but tons of good stuff from battery engineers on the web. All it takes is a little googling to find ...

A worthy reference is here http://www.batteryuniversity.com/parttwo-34.htm
 
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