Clarification regarding fully discharging a Macbook Pro built-in battery

nbar,

I took that to mean to do the (at least) monthly discharge down to 20% rather than to single digit percentages.

nbar,

the second part — as maintenance rather than as calibration. It could well be that I misinterpreted their intent, but my misinterpretation has been working well for me so far.

nbar wrote:

Apple's support article implies a full discharge once a month, IMO. i could be reading out of context, but I feel as though they would specify if they meant otherwise: IE "Apple recommends a discharge down to, but not below, 20% once a month.

In that portion, no percentages are explicitly given and I do understand that it could be interpreted as a full discharge. That though would be wrong. I use the information available in Battery University as my guide where the author indicates that total discharges have a negative impact on battery life.

In principle I agree with Melophage though I usually tell the OP to discharge to the 40% level prior to recharging the MBP.

Ciao.

nbar wrote:

Apple, however, also states:

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

My assumption is that was written by Apple before the non-removable batteries, and has not been updated for whatever reason. I believe that for unibody MBPs, the more recent advice of deep discharge calibration being unnecessary is intended to be the current advice.

This truly *****, before, Apple used to recommend power cycling devices, so I think many of us still had that same misconception for newer Apple devices.

I own the latest MBP Retina 13', and I don't use the battery that much. Not knowing about the switch in advice my battery unintentionally drained two different times (5-6 hrs followed before I recharged), and I've noticed inconsistent performance, meaning remaining time varies widely, even if I'm only browsing.

I downloaded the Battery Health App and it shows 17 cycles in 9.2 months, 99% health, with current max 6284mAh, out of original max of 6330mAh. Numbers seems fine, so I can't understand the change. Same numbers on the system report.

Is there a possibility for the battery being damaged on those two occasions, all tho numbers say contrary? MBP's still under warranty, but I guess the techs at the Genius Bar will say the battery is good.

I'd like to hear on thoughts on it... thanks!

davfranco wrote:

Is there a possibility for the battery being damaged on those two occasions, all tho numbers say contrary? MBP's still under warranty, but I guess the techs at the Genius Bar will say the battery is good.

I'd like to hear on thoughts on it... thanks!

I don't know why you're seeing strange performance, but my opinion is that two full discharges should not permanently damage the battery. I think it would have to go through a lot more than that before negative effects would happen. But I don't work for Apple so I don't know for sure.

There is such a thing as over-discharging Li-ion batteries, but a consumer has to work pretty hard to get it to happen, and when it does happen the battery can't be used. That clearly isn't happening here. Like all companies that use Li-ion batteries, Apple has a protection circuit that watches in case voltage drops to a certain cutoff threshold and if you hit that, it shuts off the hardware before the battery is really truly drained. The following article might be helpful; the section in it that applies to this is "Over-discharging Lithium-ion" so you can scroll down to that.

Charging Lithium-ion

At only 17 cycles over 9 months, I am not sure if the power manager in OS X has enough usage data to accurately predict remaining charge. I wonder if the battery estimates will smooth out over time. Most users go through maybe 100-200 cycles a year.

sorry guys, so how do you manage your battery exactly? Doesn't keeping the laptop constantly on power also damage the battery? I work on my 13" MBP with retina display constantly.

paolaEdi wrote:

Doesn't keeping the laptop constantly on power also damage the battery?

It isn't the worst thing you can do. The worst thing you can do is empty the battery to 0 every day. Keeping the laptop on AC power is not great, but as long as you use it on battery every few days it will probably be OK. There can be increased battery deterioration if the laptop is plugged in, the battery is at 100%, and the battery is exposed to high temperature, see Table 3 in How to Prolong Lithium-based Batteries. Table 2 explains why deep discharges should be avoided.

Generally, the laptop battery is designed to last longest if it is sometimes plugged in and sometimes unplugged, and when unplugged it is discharged usually to more than 50% before being plugged in again. If you leave it plugged in a lot, maybe set a calendar reminder to use it on battery for a while, every few days.

My MacBook Pro is plugged in most of the day, and used on battery about 2 hours a day. My battery is 2.5 years old and using the practices above, still reads 95% of original capacity after over 400 cycles.

You will never prevent a Li-ion battery from deteriorating because it is going to lose charge capacity over time even if it is never used. All you can do is slow it down.

Many thanks Network23 - currently (but I've only had my MBP for a couple of months) I work on battery, then charge it when it reaches about 20% (though sometimes I do not notice and goes lower), then plug it in up to 100%, then disconnect until it goes to 20%, and so on. I work from home a lot, and in a full day it can go through almost two full charges (from 20).

I think I should get used to switching it off at night.

Also, I am planning to use it remotely when commuting to/from work by connecting my iPad with parallels - but in that case I'll have to leave it plugged in, otherwise it will not wake up, but from what you say this should not be a big issue then. Still wonder whether a closed lid may result in overheating that may damage the battery?

Thanks for your help!

paolaEdi wrote:

Many thanks Network23 - currently (but I've only had my MBP for a couple of months) I work on battery, then charge it when it reaches about 20% (though sometimes I do not notice and goes lower), then plug it in up to 100%, then disconnect until it goes to 20%, and so on. I work from home a lot, and in a full day it can go through almost two full charges (from 20).

If that's what you have to do to get your work done, that's fine. If you had a choice I'd say plug it in at a somewhat higher percentage, but if that isn't practical then some additional battery deterioration may simply be a cost of doing business, like if you have to spend more on gasoline for a company car. Changing at 40 or 50% may be better than 20%, but 20% is still better than going to zero.

paolaEdi wrote:

I think I should get used to switching it off at night.

I just sleep mine because in the morning I like to pick up where I left off. I dislike having to reopen a bunch of apps and documents.

paolaEdi wrote:

Also, I am planning to use it remotely when commuting to/from work by connecting my iPad with parallels - but in that case I'll have to leave it plugged in, otherwise it will not wake up, but from what you say this should not be a big issue then. Still wonder whether a closed lid may result in overheating that may damage the battery?

It can depend on how you set it up. There are still ventilation slots that don't involve the keyboard, but I think leaving the lid open does help a little. If it's closed on an uncluttered desktop it might be OK. What is a problem sometimes are people who slide the closed laptop into a shelf or home theater cabinet with not a lot of room around it and over it, the restricted ventilation can encourage overheating.

If I was going to leave it on a desk running at home and I was concerned, I might decide to point a low-speed household fan at it. One of my old PowerBook laptops would get hot and pointing a small fan at it made a big difference.

If that's what you have to do to get your work done, that's fine. If you had a choice I'd say plug it in at a somewhat higher percentage, but if that isn't practical then some additional battery deterioration may simply be a cost of doing business, like if you have to spend more on gasoline for a company car. Changing at 40 or 50% may be better than 20%, but 20% is still better than going to zero.

It is actually due to my previous wrong conviction that it had to go down to 20% - I'll change it to 40% then, will be careful.

Thank you for your detailed answer!

NBar, network23 Thanks to both of you for your take on my "issue". I guess as you said the battery cycles are still low and the OS is not yet able to get accurate readings from the battery. I'll try to use it on battery some more but to keep it over 50%

thanks again!