Why don't E-readers have a Replaceable Battery

[ottischwenk]

Originally Posted by mdp

batteries do not like being charged frequently.

Where did you get this long outdated misinformation? Modern batteries have a certain number of total charge cycles and must not be over-discharged.

[JSWolf]

Originally Posted by shalym

You do realize that you can still buy new e-readers without buttons, right? As for wanting to turn a solar charger on and off, you could do that with a cover

Shari

But I cannot buy a new Kobo with a 7" or 8" screen without buttons.

[JSWolf]

The reason Readers don't have replaceable batteries is that Readers can last longer then the batteries and when the battery drains too fast, the user just replaces the Reader instead of the battery.

[ps67]

Originally Posted by JSWolf

But I cannot buy a new Kobo with a 7" or 8" screen without buttons.

I don't know in USA but here Kobo Aura One is still on sale. Some months ago it disappeared from Kobo site and we all thought that they wouldn't make it anymore, but then it appeared in the store again.

[mdp]

Originally Posted by ottischwenk

Where did you get this long outdated misinformation? Modern batteries have a certain number of total charge cycles and must not be over-discharged.

You have written it yourself: «Modern batteries have a certain number of total charge cycles».
I wrote «batteries do not like being charged frequently»: n/period vs 2n/period is a frequency to me.
If I have a device connected indoors I plan for the full charge, when I have a power bank outdoors I only cover a fraction of the capacity (mobility: now I can keep it connected, now I have to move and disconnect), and I assume that this will decrease its life, according to what you yourself have written.
I always interpreted that "total charge cycles" as "even partial capacity charge" (not 1-charge cycle = close to full capacity, say 15% to 100%), but I am not sure of it, I could not find the time to really study the matter on the more competent sources and rumors swing from one idea to its contrary.

I admittedly am sometimes not as clear as possible, but there is a tradeoff with how much time I have to spend per post. I check and edit my posts on an average many times, but I do not always have the time to polish.

Anyway, my best source for information about batteries, which I never had the time to study properly, would be batteryuniversity.com

EDIT: it must anyway be noted, that such "number of total charge cycles" must be very high for high quality batteries, because for tethering - for frequent charge and disconnection - I use the original battery which came with the phone: it has become very markedly fattened, but as a battery it still works like a charm after 5 years of "mistreatment".

[ottischwenk]

It's very simple: a full charge means 5 * 20% charge or 4 * 25% charge or 2 * 50% charge or 10 * 10% charge or 2 * 20% + 2 * 30% charge.
It is only important that there is no deep discharge.
Using a PowerBank corresponds to a partial load and is completely unproblematic.
There were problems with the partial charging with nickel + X batteries

[mdp]

Originally Posted by ottischwenk

It's very simple: a full charge means 5 * 20% charge or 4 * 25% charge or 2 * 50% charge or 10 * 10% charge or 2 * 20% + 2 * 30% charge.
It is only important that there is no deep discharge.
Using a PowerBank corresponds to a partial load and is completely unproblematic.
There were problems with the partial charging with nickel + X batteries

I see. I instead interpreted that if a 5000mAh battery at 20% is charged 4 times of 1000mAh, or once for 4000mAh, the effected "charge cycles" may change (and of course be higher in the first case).
I noticed from the fact that now, possibly also in a rush, you have written <</full/ charge>> (creating somehow a tautology), there exists an ambiguity in the expression 'total charge cycles': I always read it as 'total (charge cycles)', while your reading appears to be '(total charge) cycles'.
BTW: do you have a good source for this info?

[Quoth]

It is the total cycles in terms of percentage discharge and charge totalled to full cycles, when discharge is to no less than 1/4 to 1/3rd and full charge is no more than 2/3rds to 3/4. Full discharges and full charges, elapsed time and elevated temperature all shorten life. Charge controllers actually disconnect the cell before its fully discharged and stop even trickle charging above a certain point. They vary on how well they are implemented and some "lock" out charging when a certain number of equivalent total cycles are reached. The Kindle keyboard has a controller/sensor in the cell pack and on the main board. It will eventually stop charging a cell even if it's not completely worn out (though that was a 10 year old cell).
The NiCd had a memory effect, also they could grow nickel dendrites that would short the cell.
The NiMH has no memory effect but is damaged by a level of trickle charge when "full" that's acceptable for NiCd.
Both self discharge, though some purer NiMH take a year, NiCd can take a week. Both will last almost indefinitely if stored discharged. The Lithium cells need stored at 1/3rd to 2/3rds and thus are often shipped at 2/3rds charge.
Lead Acid cells sulfate if left flat. They need to be stored dry (30+ years shelf life) or fully charged. It's a retrograde step that Lead Acid are now retailed "pre filled" with the sulphuric acid as they deteriorate.
NiCd and NiMH are destroyed if reverse charged often by a stack (6V, 9V, 12V etc battery packs) being repeatedly run flat (less than 1.1V per cell) as the cell that is discharged first is reverse charged by the others in use.
Lithium cells go on fire if reverse charged, or if it's attempted to charge a truly flat cell. That's why laptops etc have a cpu dedicated to the cells and measure the voltage of every cell in the series chain.

You can even cause single use lithium coin cells to explode or go on fire. The -ve terminal plate can be flung 20m away. I've photos.

It's technically possible to recharge Alkaline cells, but they can't be trickle charged when full and must not be charged when less than about 1/2 discharged, so no-one does it, as it makes more sense to use the rechargeable lithium cells.

Turbo charging of NiCd or NiMH is hazardous, though I only exploded one set of NiiMH designing the charger. It does shorten the life.

The batteryuniversity site is quite good, but not the whole story.

Don't buy battery versions of any tool or appliance where the mains is convenient. It's heavier for same power due to the batteries, less environmentally friendly (making cells and loss in recharging) and life may be only 12 to 30 months.

[cfrizz]

When I'm home my phone is connected to a charger, I simply buy a new battery for my Note 2 once a year or year and a half.

[John F]

Originally Posted by mdp

I see. I instead interpreted that if a 5000mAh battery at 20% is charged 4 times of 1000mAh, or once for 4000mAh, the effected "charge cycles" may change (and of course be higher in the first case).
I noticed from the fact that now, possibly also in a rush, you have written <</full/ charge>> (creating somehow a tautology), there exists an ambiguity in the expression 'total charge cycles': I always read it as 'total (charge cycles)', while your reading appears to be '(total charge) cycles'.
BTW: do you have a good source for this info?

Check out Battery University.

[Apache]

Originally Posted by John F

Check out Battery University.

Be careful using battery stores and letting them change your watch batteries. I get quite a few customers coming in with damaged watches after letting them change their batteries. I have had a number of customers that took solar watches in and they put a regular watch battery in them. They are almost as bad as Wal Mart when it comes to damaging watches.
Apache

[John F]

Originally Posted by John F

Check out Battery University.

Originally Posted by Apache

Be careful using battery stores and letting them change your watch batteries. I get quite a few customers coming in with damaged watches after letting them change their batteries. I have had a number of customers that took solar watches in and they put a regular watch battery in them. They are almost as bad as Wal Mart when it comes to damaging watches.
Apache

I meant the website for Battery University. Are they also a battery store?

[mdp]

Originally Posted by Quoth

It is the total cycles in terms of percentage discharge and charge totalled to full cycles, when discharge is to no less than 1/4 to 1/3rd and full charge is no more than 2/3rds to 3/4. Full discharges and full charges, elapsed time and elevated temperature all shorten life

So, it seems that 15%→85% suboptimal, 30%→70% would be "more optimal", and 40%→60% possibly even better. But again none of these (see at the bottom), I understand, represents an "official charge cycle".

Interestingly, I see a table at
https://batteryuniversity.com/index....ased_batteries
according to which (reinterpreting for the purpose of a more practical numeric comparison) a 1Ah LiPO4 battery can be charged
-- for its 80% around 900 times which is for 720Ah, or
-- for its 20% around 9000 times which is for 1800Ah.
Charging small amounts can overly double the life of the battery.

From the same page:
important:
«Cycling between 85 and 25 percent ... provides a longer service life than charging to 100 percent and discharging to 50 percent»
Interesting:
«The smallest capacity loss is attained by charging Li-ion to 75 percent and discharging to 65 percent ...»
Funny:
«... This, however, does not fully utilize the battery [← having to recharge every 10% loss]»

Originally Posted by mdp

I always interpreted

Originally Posted by ottischwenk

It's very simple

Originally Posted by Quoth

It is

I find it funny to now read at the same page at batteryuniversity.com
«[...] there are no clearly defined standards of what constitutes a cycle»

[ottischwenk]

Do you want to scientifically charge and discharge just to double the battery life at best?
It is enough for me to use the device and to charge at about 40-50%

[mdp]

Originally Posted by ottischwenk

Do you want to scientifically charge and discharge just to double the battery life at best?
It is enough for me to use the device and to charge at about 40-50%

: ) Oh, you winking tongue-in-cheek you.

Of course not: it is political. It is to build awareness, about how things are and how things are not. Dissipating ignorance - that healthy side of Illuminism -, that tradition of looking at things that comes from Galileo. Because without that strive and effort, that orientation and exercise, people remain beasts and morons, which will be a problem because most countries has settled for naïve democracies and widespread professional empowerment, and in fact following some statistics only a tiny handful of countries over 200 sees the median citizen in the side of the more prepared ones.

Otherwise, you would not know that it is a good idea to «charge at about 40-50%».
That «[little more than] double the battery life at best» was not known to me before checking those tests yesterday, and it surely will be a surprise for many.

As an example of all that is still unemerged, for my original suspect that charging for 1000mAh in a single session or in ten steps of 100mAh each may not be the same, I take note of your suggestion that the number of steps is irrelevant, but it would be better to have some graph like the one above, some test results or deduction, because I did find this data up to now surprising.