Mobileread
Forma how do sleep and power-off differ, with regards to battery consumption
#1  droopy 08-21-2019, 10:04 AM
What's the difference between sleep and power-off? (Like, with regards to power/battery) .

People on this forum have pointed out that an ereader doesn't use energy to maintain the e-ink on the screen (unlike a phone/tablet displaying stuff on their screen). Is this true?

If my forma's light is off (0%), is there any advantages to powering off?
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#2  the.Mtn.Man 08-21-2019, 10:20 AM
Yes, it's true that e-ink displays do not require power to maintain the image.

As for the difference between sleeping and fully powered off, I'm not sure there is much of one. If I had to guess, sleep mode uses only enough energy to power the RAM allowing the e-reader to wake instantly, and the energy used is likely no more than the natural discharge rate of an idle rechargeable battery. I've also seen the suggestion that any energy saved by powering off is offset by the energy used during the power-on sequence.

Speaking in practical terms, my first generation Kobo Aura used daily with the front light can go for several weeks between charges, and I never fully power it off.
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#3  droopy 08-21-2019, 10:33 AM
Thanks for your reply, MtnMan.

How much energy does it take when the unlit Forma isn't asleep (nor powered off)... when the Forma is just maintaining the eink? You mentioned RAM in the context of waking. I wonder if energy is used with regard to RAM when Forma is simply maintaining eink text.
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#4  Tarana 08-21-2019, 11:03 AM
In my unscientific experience, the differences between using sleep/wake cover and actually powering off is not very significant over a 2 week period. Not using a sleep/wake cover, especially if you are picking your book up several times a day, does have more loss of energy over the same period. Keep in mind, in sleep mode, your unit is still hooked to wifi. This allows overnight updates as well as subscription download. If you have wifi totally turned off, I doubt there is much difference between sleep/wake and fully turned off over 2 week period.
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#5  droopy 08-21-2019, 11:08 AM
Tarana, Thanks for your comment. (Nice dinosaur profile pic! I hereby nickname you Tarana-saurus Rex. ha ha)

Good point about wifi. I have Wifi competely off. Does this mean that my unlit, no-wifi Forma uses the same energy when it's on a page while awake/on as it does when it it's asleep/off? (In other words, zero energy consumption?)
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#6  NiLuJe 08-21-2019, 12:18 PM
It's non-zero, but not much.

Unless you have some fairly esoteric needs (i.e., keeping the device on a single page for a large amount of time (think sheet music)), and provided you use it regularly, the defaults should be pretty sane (i.e., auto-suspend after a while (like, 15 or 30 min of inactivity), and auto-poweroff never).

If you do need to keep your device inactive for a while (say, in storage for > 2 weeks), then you might consider powering it off.

Other than that, you might have been restarting a holy war on the subject of sleep vs. poweroff .
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#7  DNSB 08-21-2019, 12:19 PM
Quote droopy
Tarana, Thanks for your comment. (Nice dinosaur profile pic! I hereby nickname you Tarana-saurus Rex. ha ha)

Good point about wifi. I have Wifi competely off. Does this mean that my unlit, no-wifi Forma uses the same energy when it's on a page while awake/on as it does when it it's asleep/off? (In other words, zero energy consumption?)
When your ereader is awake, it consumes more energy than when in sleep. If nothing else, the touch screen needs to be scanned while awake.
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#8  droopy 08-21-2019, 01:42 PM
Quote NiLuJe
Other than that, you might have been restarting a holy war on the subject of sleep vs. poweroff .
Oooh. Let's stay quiet about the matter then.
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#9  the.Mtn.Man 08-21-2019, 01:53 PM
Quote Tarana
Keep in mind, in sleep mode, your unit is still hooked to wifi. This allows overnight updates as well as subscription download. If you have wifi totally turned off, I doubt there is much difference between sleep/wake and fully turned off over 2 week period.
That's a good point. I never use WiFi.
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#10  ratinox 08-22-2019, 10:25 AM
Quote droopy
What's the difference between sleep and power-off? (Like, with regards to power/battery) .

People on this forum have pointed out that an ereader doesn't use energy to maintain the e-ink on the screen (unlike a phone/tablet displaying stuff on their screen). Is this true?

If my forma's light is off (0%), is there any advantages to powering off?
To answer the final question: yes, with a caveat.

When sleeping some of the device is powered off (lights, screen input) but parts are still running: the processor is running the OS, WiFi will be activated for automatic sync, etc. My Aura One will drain the battery in a month or two while sleeping.

When powered off everything is shut down except for a miniscule trickle for the power soft switch (so it's not truely off, but close enough for most practical purposes). My Aura One powered off for a month isn't noticeable.

Here's the caveat: turning the device on is a relatively large burst of power starting the OS and loading the home screen application. Whether or not this is better than sleep depends on how long the device is powered off or sleeping between use. Probably not worth turning off on a day-to-day basis but probably is worth turning off for week or two intervals or longer.
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