Charging tablets and mobile phones in the case.

[studiot]

If you have your phone or tablet in a protective case, additional to the tablet itself,

does anyone know or have any data on how safe it is to leave the device in the case for charging or should it always be removed ?

[iNow]

Risk is so negligibly small IMO as to be dismissed and disregarded. Main risk seems to be fire from heat. If your device is getting so extremely hot while it charges as to ignite any items surrounding it, then case or no case will result in similar outcomes. It’s time to replace. 

The only time it makes sense to remove a case for charging IMO is if you’re using a wireless induction pad and the case interferes with successful transfer of power. 

[StringJunky]

From what I learned a few years ago, when vaping devices were relatively new, is don't let the battery go below 20% as a rule. Charging from an exhausted state repeatedly is what causes the risk. For reasons that escape me now, lithium metal can be formed under circumstances of re-charging under very low charge. TLDR: Always top-up  a Lithium-ion battery. It likes to be charged up. Top-up is good; Deep discharge and re-charge will degrade the battery faster and more likely create the internal conditions for lithium metal and a fire to form. 

e2a it might be below a residual 2.5v that things  can become risky. The operating voltage range is 3.3-4.3v I think.

Most of my learning info on this subject came fro  the Battery University site iirc.

 

Edited August 20, 2023 by StringJunky

[mistermack]

10 minutes ago, StringJunky said:

Always top-up  a Lithium-ion battery. It likes to be charged up.

That's worth knowing. 

I've only come unstuck once, I had a cheap pen/camera, and left it charging, and the battery cooked and died. Most reasonable quality stuff will have a circuit that prevents overcharging, but going by that pen, cheap stuff might not. 

Or maybe that was a one/off, and you can't overcharge lithium? I don't know.

[StringJunky]

22 minutes ago, mistermack said:

That's worth knowing. 

I've only come unstuck once, I had a cheap pen/camera, and left it charging, and the battery cooked and died. Most reasonable quality stuff will have a circuit that prevents overcharging, but going by that pen, cheap stuff might not. 

Or maybe that was a one/off, and you can't overcharge lithium? I don't know.

All lithium devices should have control circuits because the voltage parameters I mentioned must be adhered to (AFAIK) for safe storage and operation.  A devices circuit should cut off device use between 2.8 -3.3v  and notify recharging.  Maximum is 4.4v. Fast chargers should be avoided in general as high internal charging temps degrade battery life. The better fast ones have fans blowing on the batteries.

 

I don't cheap out on Li-ion stuff. I use car battery standard batteries where I can.

Edited August 20, 2023 by StringJunky

[TheVat]

Some devices have a drain feature* which, after you reach 100% will start to drain the battery in order to prevent overcharge.  That's why my tablet, if I forget and leave it on charger all night, will be at 88-95% in the morning.  It reached 100% at say 3 am, then started going down.  Seems like a better device would just break the circuit at full charge.

* maybe bug is a better term

Edited August 20, 2023 by TheVat
aster isk

[StringJunky]

2 minutes ago, TheVat said:

Some devices have a drain feature* which, after you reach 100% will start to drain the battery in order to prevent overcharge.  That's why my tablet, if I forget and leave it on charger all night, will be at 88-95% in the morning.  It reached 100% at say 3 am, then started going down.  Seems like a better device would just break the circuit at full charge.

* maybe bug is a better term

The drop is probably the charges continuing distributing after it's stopped charging; evens out and the final voltage drops a bit.

[TheVat]

2 minutes ago, StringJunky said:

The drop is probably the charges continuing distributing after it's stopped charging; evens out and the final voltage drops a bit.

That would make more sense.  I don't well understand "charges continuing distributing" when the device is completely shut off, but assume that's inherent in the battery design.

[StringJunky]

19 minutes ago, TheVat said:

That would make more sense.  I don't well understand "charges continuing distributing" when the device is completely shut off, but assume that's inherent in the battery design.

I assumed it's a chemical process induced by electricity,  and those don't stop straightaway into a static state when the power turns off. I imagine there will be internal processes, like ion distribution, still moving towards equilibrium throughout the cell. When everything has balanced, the reading at the physical location of the voltage sensor should be lower.

Edited August 20, 2023 by StringJunky

[studiot]

Having dried my thermometer out I can report the following measurements

 

Lenovo M8 tablet

Battery 5000mAh

reported power idle 0.5W, loaded 4W.

Charger 2A usb = 10W

Cover wallet constructed of leatherette covered card.

Screen exposed, rest covered.

 

Ambient temperature  23 C

Tablet working temp at 40% charge 26.5 C, working on battery alone.

Tablet switched off

After 1 hour tablet cooled to 24.2 C

Charging started

 1/2 hour after commencement of charging, tablet @ 28.5 C

 1 hour after commencement of charging, tablet @29.9 C

 2 hours after commencement of charging, tablet @26.9 C

3 hours after commencement of charging tablet @ 28.5 C

Reboot charge still connected charge 99%

3.5 hours after commencement charging tablet @ 28.5 charge 100%