lithium primary coin cell in parallel?
 

I have just purchased a commercial device from the far east which is
powered by two CR2032 lithium coin cells connected in parallel.

I can see no positive reason for this at all and some negative ones

The operating current is 60uA and 16uA on standby which it reverts to
after 5mins in activity.
I have sometimes seen these cells paralleled up to meet a peak current
requirement but there is nothing like that sort of current being drawn
by a couple of chips and a LCD display

Each cell is rated at 230mAh which should give around 3800 hours normal
operation and 14000 in standby so well over a year with mixed duty cycle.

SO why on earth are there two cells fitted??


Any clues?

Bob

PS it is a digital readout scale - a bit like the cheapo verniers but a
lot longer.

lithium primary coin cell in parallel?
 

"Bob Minchin" wrote in message ...
I have just purchased a commercial device from the far east which is powered by two CR2032 lithium coin cells connected in
parallel.

I can see no positive reason for this at all and some negative ones

The operating current is 60uA and 16uA on standby which it reverts to after 5mins in activity.
I have sometimes seen these cells paralleled up to meet a peak current requirement but there is nothing like that sort of current
being drawn by a couple of chips and a LCD display

Each cell is rated at 230mAh which should give around 3800 hours normal operation and 14000 in standby so well over a year with
mixed duty cycle.

SO why on earth are there two cells fitted??


Any clues?

Bob

PS it is a digital readout scale - a bit like the cheapo verniers but a lot longer.

Does it have any settings or calibration data stored in volatile memory?

Perhaps the idea is you replace the cells one at a time before either
is exhausted.


--
Graham.

%Profound_observation%

lithium primary coin cell in parallel?
 

Graham. wrote:
"Bob wrote in message ...
I have just purchased a commercial device from the far east which is powered by two CR2032 lithium coin cells connected in
parallel.

I can see no positive reason for this at all and some negative ones

The operating current is 60uA and 16uA on standby which it reverts to after 5mins in activity.
I have sometimes seen these cells paralleled up to meet a peak current requirement but there is nothing like that sort of current
being drawn by a couple of chips and a LCD display

Each cell is rated at 230mAh which should give around 3800 hours normal operation and 14000 in standby so well over a year with
mixed duty cycle.

SO why on earth are there two cells fitted??


Any clues?

Bob

PS it is a digital readout scale - a bit like the cheapo verniers but a lot longer.

Does it have any settings or calibration data stored in volatile memory?

Perhaps the idea is you replace the cells one at a time before either
is exhausted.


Good call!
That would enable the current position to be retained but if that were
the design idea, they have not bothered to mention it in the instructions.
The only indication of low battery is a flashing display and as the
cells are hardwired together, they would be no indication of which had
failed. Indeed connecting them that way means their terminal voltages
are identical and so possibly have similar remaining charge in each.

Bob

lithium primary coin cell in parallel?
 

on 28/07/2011, Bob Minchin supposed :
The only indication of low battery is a flashing display and as the cells are
hardwired together, they would be no indication of which had failed. Indeed
connecting them that way means their terminal voltages are identical and so
possibly have similar remaining charge in each.

Usually the minimum voltage required for memory retention requirements
is much lower than the minimum required for operation.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

lithium primary coin cell in parallel?
 

"Bob Minchin" wrote in message
...
Graham. wrote:
"Bob wrote in message
...
I have just purchased a commercial device from the far east which is
powered by two CR2032 lithium coin cells connected in
parallel.

I can see no positive reason for this at all and some negative ones

The operating current is 60uA and 16uA on standby which it reverts to
after 5mins in activity.
I have sometimes seen these cells paralleled up to meet a peak current
requirement but there is nothing like that sort of current
being drawn by a couple of chips and a LCD display

Each cell is rated at 230mAh which should give around 3800 hours normal
operation and 14000 in standby so well over a year with
mixed duty cycle.

SO why on earth are there two cells fitted??


Any clues?

Bob

PS it is a digital readout scale - a bit like the cheapo verniers but a
lot longer.

Does it have any settings or calibration data stored in volatile memory?

Perhaps the idea is you replace the cells one at a time before either
is exhausted.


Good call!
That would enable the current position to be retained but if that were the
design idea, they have not bothered to mention it in the instructions.
The only indication of low battery is a flashing display and as the cells
are hardwired together, they would be no indication of which had failed.
Indeed connecting them that way means their terminal voltages are
identical and so possibly have similar remaining charge in each.

Bob


Sounds feasible. I've had instructions on a big programmable calculator
warning you to change the batteries one at a time so as not to lose memory
contents.

rusty