Run off battery or PSU?

With modern day battery technology it does not matter. GGJstudios will post a helpful post on batteries in a moment.

Spikeywan said:

Most of the time, when using my rMBP I have access to mains electricity.

Should I just run it off the power supply, or should I run it off the battery until it warns me to charge it, then only leave the power supply connected until the battery is fully charged again?

Thanks.

Click to expand...

Run on battery whenever you need to and plug it in whenever you can. You can plug or unplug any time you need to, regardless of the charged percentage, and you never need to completely drain your battery. Just make sure you don't run on AC power exclusively, as your battery needs to be used regularly to stay healthy. The link below should answer most, if not all, of your battery/charging questions. If you haven't already done so, I highly recommend you take the time to read it.

Spikeywan said:

Thanks. I spotted an interesting point, which I would never have thought of... When hammering the machine, playing a game or similar, plugging the charger in will make it run faster.

Click to expand...

Where did you read that?

GGJstudios said:

...Just make sure you don't run on AC power exclusively, as your battery needs to be used regularly to stay healthy.

Click to expand...

Lots of great info in your posts. However, I'm not sure I buy the idea that I keep hearing here that the battery must be used regularly to stay healthy. Apple points out that batteries are consumable items and charge cycles are the primary way they are "consumed".

Note that Lithium batteries store very well - up to 10 years when stored at cool temperatures and moderate charge. They don't need to be continually cycled to stay healthy.

Unfortunately, standard use is very different from the ideal storage conditions. Laptop batteries tend to be in a hot enclosure and and usually at full charge (even if they are often cycled).

There's lots more great battery info here:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
http://batteryuniversity.com/learn/article/how_to_store_batteries

KevinC867 said:

Lots of great info in your posts. However, I'm not sure I buy the idea that I keep hearing here that the battery must be used regularly to stay healthy. Apple points out that batteries are consumable items and charge cycles are the primary way they are "consumed".

Click to expand...

It has been proven countless times that running on AC power exclusively will shorten a battery's life. That's why Apple recommends running on battery power regularly.

KevinC867 said:

Note that Lithium batteries store very well - up to 10 years when stored at cool temperatures and moderate charge. They don't need to be continually cycled to stay healthy.

Click to expand...

Storage is a completely different topic than using the battery. For storage, Apple recommends a 50% charge. See the Battery FAQ for details.

KevinC867 said:

Unfortunately, standard use is very different from the ideal storage conditions. Laptop batteries tend to be in a hot enclosure and and usually at full charge (even if they are often cycled).

Click to expand...

The regular use recommendation still applies.

KevinC867 said:

There's lots more great battery info here:

Click to expand...

Don't trust everything you read at batteryuniversity.com, as the information there is quite generic and may not specifically address the battery technology employed by Apple in its notebooks. A more reliable and trustworthy source is Apple itself, since they have a vested interest in making sure their batteries perform as advertised.

Spikeywan said:

Thanks. I spotted an interesting point, which I would never have thought of... When hammering the machine, playing a game or similar, plugging the charger in will make it run faster.

Click to expand...

Isn't that only when you have energy saving features on that limit CPU power when the computer is running off battery?

Having just recently received my rMPB would it be correct to assume that when I have access to an AC run it off that and then once in a while take it off the AC and run it on the battery?

Running it primarily on AC and then switching to the battery wouldn't do the battery any harm in terms of longevity, correct?

Thanks in advance.

Spikeywan said:

This is why you may find your battery may temporarily stop charging or even drain somewhat, even though you have your AC adapter plugged in. This is working as designed and will only be used during periods of peak power demands.

Click to expand...

That doesn't mean your computer will run faster. It just means it can draw power from both AC and battery during periods of high demand. Whether it's plugged in or on battery, it will run at the same speed.

Mwam said:

Having just recently received my rMPB would it be correct to assume that when I have access to an AC run it off that and then once in a while take it off the AC and run it on the battery?

Running it primarily on AC and then switching to the battery wouldn't do the battery any harm in terms of longevity, correct?

Click to expand...

Read the 3rd post of this thread.

Spikeywan said:

Why would it need power from both the battery and the charger? The harder it works, the more power it uses, right?

So if it only had battery power, or only had charger power, then surely it wouldn't have enough power to run at full tilt, therefore it would need to run at reduced power, which would equate to being a bit slower.

Click to expand...

If it only had battery power available, it wouldn't slow down. It would simply drain the battery faster. If you removed the battery and only ran on AC power, it would throttle the CPU and run slower. That isn't going to happen on a Mac notebook with a non-removable battery.

GGJstudios said:

Where did you read that?

Click to expand...

At least with Wintel machines, it's typical for it to run on a "battery profile" when not on AC, which between several things, slows down the cpu clock a bit for obvious purpose. I dunno if this is true of Macs.

Mrbobb said:

I dunno if this is true of Macs.

Click to expand...

No, it's not.