Wallmount tablet: battery handling. Always 100% charged or maintain battery at a certain level?

Apps & Services HABPanel
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1

This question is not really openHAB related, but I was wondering, if the community has some good ideas.

I have hung an iPad on the wall and it’s running the HABpanel 7x24.
I wonder what is better for the iPad’s battery:

  • always plugged in (and always at 100% charge)
  • keeping the battery charge between 60% and 80% with a switchable socket (ShellyPlug)
  • keeping the battery charge between 1% and 80% with a switchable socket

Are there any recommendations as to what is “healthier” for the battery?
A rule to maintain the battery level between 60% and 80% could look like this:

rule "iPad HABpanel"
when 
    Item iCloud_iPad_Battery received update or 
then 
    if (iCloud_iPad_Battery.state < 60) {
        if (ShellyPlug.state == OFF){
            ShellyPlug.sendCommand(ON) 
        }
    }
    if (iCloud_iPad_Battery.state > 80) {
        if (ShellyPlug.state == ON){
            ShellyPlug.sendCommand(OFF) 
        }
    }
end

Thanks for your ideas :slight_smile:

2

Between those three number 2 is the best.
Deep discharges are the worst regarding lifespan of lithium-cells. Manufacturers usually deliver new cells with around 80% or less for lowest stress.
The number of cycles is not so relevant for the lifespan.
As the charging strategy of mobile devices is heavily optimized for capacity the common LCO-cells are even overcharged when charged to 100% which decreased lifespan (but maybe this is even welcome :wink:)
I only reduce the max to 80% (possible with some android devices) and keep it plugged all the time so that the internal battery management handles charging cycles. If the max can be reduced there’s no need for a fancy rule to ensure a certain discharge.
As a summary: Pretty much everything is different than with the old NiMH-rechargeables.

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3

I’d add that even 80% isn’t really necessary since the tablet will always be AC-powered (except in an outage). The 80% max setting on some phones/tablets is more about balancing daily use versus long-term health. You’re just trying to reduce stress on it, so you don’t have to go up to 80%.

Something to keep in mind is if the smart plug you use makes an audible click when it toggles. That can get annoying throughout the day and night. If so, you might want to add some other conditions to reduce the toggling. For example, maybe it only charges when the display is on.

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4

Agree that the first option is probably the worst one. See also my report here about bloated batteries, happened to me twice already.

5

I also have one of Android tablets used as HABPanel display. My device can’t limit the maximum charge so I used similar approach like you with shelly controlled socket.

I use Fully Kiosk Browser as displaying app and it can report several measurements back to openhab, like battery temperature, charging state and even can control the screen.

Then I have several rules which keep battery charging between 40 - 65 % and only switch on the charging when battery temperature is below 40 °C. Then I use near motion sensor and turn the screen off when there is no motion for several minutes and back on when somebody is around.

So I would recommend to go with second option and keep the charging level around 50 %

1 Like