On 12:00 24 Dec 2019, newshound wrote:

On 23/12/2019 22:25, Pamela wrote:
On 17:55 23 Dec 2019, newshound wrote:


The issue is not safety as lithium ions batteries and chargers are
usually well protected but that the battery is stressed when it
contains a full charge. I'm told it also physically swells.

Those smartphone users trying to conserve lithium ion batteries will
not charge above 80% or so. A Dyson doesn't offer the same degree of
control but leaving it on charge the whole time continually keeps
topping up in the most stressful way.

Citation? I don't doubt that the wall-wart feeding the bracket is very
basic, but doesn't the clever control stuff live inside the battery?

Cites with breaks for clarity:

Lithium-ion operates safely within the designated operating voltages;
however, the battery becomes unstable if inadvertently charged to a
higher than specified voltage. Prolonged charging above 4.30V on a
Li-ion designed for 4.20V/cell will plate metallic lithium on the
anode.

The cathode material becomes an oxidizing agent, loses stability and
produces carbon dioxide (CO2).

https://batteryuniversity.com/learn/article/charging_lithium_ion_batteries


a Li-ion battery cycled within 75%-25% SoC (blue) would fade to 74%
capacity after 14,000 cycles.

If this battery were charged to 85% with same depth-of-discharge
(green), the capacity would drop to 64% at 14,000 cycles,

and with a 100% charge with same DoD [depth of discharge] (black), the
capacity would drop to 48%.

For unknown reasons, real-life expectancy tends to be lower than in
simulated modeling. Environmental conditions, not cycling alone, govern
the longevity of lithium-ion batteries.

The worst situation is keeping a fully charged battery at elevated
temperatures. Battery packs do not die suddenly, but the runtime
gradually shortens as the capacity fades.

...

Environmental conditions, not cycling alone, govern the longevity of
lithium-ion batteries. The worst situation is keeping a fully charged
battery at elevated temperatures.

https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries