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OK to leave Li-ion battery in charger with no power connected?

P

Paul

Jan 1, 1970
0
After I have charged my spare lithum-ion camera battery I like to
leave it in the charger with the mains disconnected.

(It's a handy place to keep the battery.)

In that sort of setup, would the disconnected charger still provide a
circuit which slowly discharges the battery?
 
R

Rich.

Jan 1, 1970
0
Paul said:
After I have charged my spare lithum-ion camera battery I like to
leave it in the charger with the mains disconnected.

(It's a handy place to keep the battery.)

In that sort of setup, would the disconnected charger still provide a
circuit which slowly discharges the battery?

Most any manufacture will state in the instruction manual to NOT leave
batteries in a charger. Leaving them in will do as you suspect, slowly drain
them.
 
S

Sjouke Burry

Jan 1, 1970
0
Paul said:
After I have charged my spare lithum-ion camera battery I like to
leave it in the charger with the mains disconnected.

(It's a handy place to keep the battery.)

In that sort of setup, would the disconnected charger still provide a
circuit which slowly discharges the battery?
Yes.
 
A

Archimedes' Lever

Jan 1, 1970
0
Contact the manufacturer of the charger. MOst of the times the
instructions not to leave them in the charger assume that it is still
plugged into the AC power line

Modern battery chargers do NOT EVER overcharge. They have monitoring
circuitry. It is YOU that is doing the assuming.

So, one should not leave them in a NON-energized charger as that WILL
deplete them. Leaving them in an energized charger will do no harm, as
the charger tapers to nil once the charge condition is met, and resumes
higher charging voltages when the criteria for charging is met. Whenever
a charged battery goes in, nothing happens (charge wise). When a
non-charged battery goes in, the charge cycle begins. There are
typically two monitors in a modern charger, and two pairs of cells or two
single 9 volt batteries can be charged at the same time, while each pair
is separately monitored. Once the charge voltage is reached, that charge
circuit goes into an idle watchdog mode.

So the battery in an energized charger will remain "topped off". The
non-energized charger will deplete a battery.
 
J

James Sweet

Jan 1, 1970
0
Paul said:
After I have charged my spare lithum-ion camera battery I like to
leave it in the charger with the mains disconnected.

(It's a handy place to keep the battery.)

In that sort of setup, would the disconnected charger still provide a
circuit which slowly discharges the battery?


It depends on the design of the charger, but in most cases there is no
harm in leaving the battery in place. Lithium battery chargers have
fairly complex control circuitry that will isolate the cell(s) from
anything else.
 
A

Archimedes' Lever

Jan 1, 1970
0
Its not plugged in so the circuit isnt complete, you would have to run
your own tests to see what happens.


It is not plugged in, so THAT AC input circuit is not complete.

The circuit that battery is attached to may well be "complete enough"
to trickle drain the battery.

You need to continue your education. Hopefully, in a field other than
electronics.
 
V

Vince Ent

Jan 1, 1970
0
It is not plugged in, so THAT AC input circuit is not
complete.

The circuit that battery is attached to may well be "complete
enough" to trickle drain the battery.

You need to continue your education. Hopefully, in a field
other than electronics.

Could the charger have some sort of isolating device such as a
capacitor in the charging circuit and thereby prevent discharge
of the li-ion battery when the charger was not energized?
 
J

James Sweet

Jan 1, 1970
0
Vince said:
Could the charger have some sort of isolating device such as a
capacitor in the charging circuit and thereby prevent discharge
of the li-ion battery when the charger was not energized?


Batteries are DC, capacitors block DC, so that won't work. Really cheap
chargers for less fragile NiCD, NiMH, and lead acid batteries use a
diode to provide both rectification and isolation. In either case, a
transformer provides isolation between the AC line and the battery.

Generally Li-ion chargers use a mosfet to control current to the cell,
and in multiple cell packs there are multiple mosfets to allow
individual control of each cell. Li-ion batteries are notoriously fussy
and require careful monitoring in both charge and discharge to keep the
voltage, current, and temperature within a relatively narrow window. At
any rate, when the charger is unplugged, the mosfets will be off, and
present essentially an open circuit. Some Li-ion cells even have their
own charge/protection circuitry built into each cell. These can be
charged using a simple current limited power source and by nature are
connected to their charger all the time.

For those curious about the chargers, check out the datasheets for some
of the common charge controller IC's out there. Texas Instruments,
Intersil, and Dallas/Maxim among others have a number of products in
that category.
 
A

Andrew Gabriel

Jan 1, 1970
0
After I have charged my spare lithum-ion camera battery I like to
leave it in the charger with the mains disconnected.

(It's a handy place to keep the battery.)

In that sort of setup, would the disconnected charger still provide a
circuit which slowly discharges the battery?

Probably an effect which is no more than the effective
self-discharge of the lithum-ion battery pack, and so nothing
to worry about providing you don't leave there for months
with no use.

If you leave the charger plugged in and it's a good quality
charger, it may periodically do a top-up charge to counteract
this. OTOH, it might not be a micropower standby product, and
there's always a minisule extra fire risk (probably significantly
less than from the lithum-ion battery itself though).
 
A

Archimedes' Lever

Jan 1, 1970
0
Could the charger have some sort of isolating device such as a
capacitor in the charging circuit and thereby prevent discharge
of the li-ion battery when the charger was not energized?

A capacitively coupled DC charger? Sounds a bit more than a little
unlikely.
 
A

Archimedes' Lever

Jan 1, 1970
0
Probably an effect which is no more than the effective
self-discharge of the lithum-ion battery pack,


Nonsense. It would have to be greater than no connection at all.

Shelf life discharge is pretty slow. Slower even than a few microamps
of discharge would be.
 
J

James Sweet

Jan 1, 1970
0
Andrew said:
Probably an effect which is no more than the effective
self-discharge of the lithum-ion battery pack, and so nothing
to worry about providing you don't leave there for months
with no use.

If you leave the charger plugged in and it's a good quality
charger, it may periodically do a top-up charge to counteract
this. OTOH, it might not be a micropower standby product, and
there's always a minisule extra fire risk (probably significantly
less than from the lithum-ion battery itself though).


Lithium batteries have negligible self discharge. Unfortunately they do
wear out just sitting there whether used or not, more quickly than NiCD
and NiMH cells do.
 
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