On Tue, 24 Dec 2019 16:02:37 GMT, Pamela
wrote:

snip


I think that's the very point he a lithium ion battery left on charge
the whole time lost most of its capacity prematurely.

I think you would have to define 'Left on charge'?

From a user POV it might be considered 'on charge' because it's
plugged into the mains and the charging light is on but it might not
actually *be* charging the battery at that point.

In the old days, basic car chargers would come with an ammeter so you
could determine, from how much current it was supplying, how charged
the battery was.

'These days', few would understand what that meant (and partly why
they don't fit engine temperature gauges to some cars nowdays).

So, any reasonable battery charger these days is likely to either show
a 'Charged' LED or the led change from flashing (charging) to solid
(charged) and the charging current cut off.

It may well continue to monitor the battery voltage and *if* it should
drop back below a certain threshold, it may provide a top-up charge.
However, the self discharge rate of these modern cells is quite low
and so it wouldn't be doing so very often or for very long (and we
don't know what charge level that actually is).

My most sophisticated / computerised muti chemistry and voltage
charger allows you to set all these values and give full BMS of up to
10 cells in series.

There are mixed messages on how adverse this is. There's better
agreement that low discharge is even worse.

Again, no expert but I thought battery life was defined by the number
of charge/discharge cycles and therefore if you kept topping up, the
battery would wear out more quickly.

Entirely depends on the depth of discharge and what state of charge. I
believe satellite batteries are optimised for longevity by avoiding
extreme charge and discharge to such a degree that they are designed to
work only within a narrow band of charge.

Not just satellite batteries but any scenario where the primary goal
is to prolong battery life.

In most systems however, where the battery capacity is limited by
size, weight or cost, lifespan has to be a compromise between useable
capacity and said lifespan.

eg, Some people push their batteries to the (safe) extremes because
the cost of that is considered acceptable.

Radio modellers are one such example.

When I was a sponsored RC electric car racer the maximum speed and
duration of the car was set by the ability of the battery to give 100%
of it's charge of the duration of one race, because even if the
batteries only lasted 25 cycles at that usage (instead of maybe 1000),
that could still be one complete season (you typically ran multiple
battery packs) and was just part of the 'cost'.


Cheers, T i m