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CR2032 maximum pulse current means what?

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rbairos

New Member
Hi,

Im considering reducing the size of some of my battery powered projects by using
the CR2032 button cell.

All the specs mention something similar:

- Standard current: 0.1mA
- Continuous current (maximum): 1mA
- Pulse current (maximum): 10mA

However I need to drive about 9 mA occassionally for brief moments.
Anyone know how *long* can the maximum pulse current can last?
I have not been able to find this information anywhere, so the specs dont help at all.

Thanks in advance!
Rob.
 

blueroomelectronics

Well-Known Member
As long as you don't expect the battery to last for ages should work fine. My Apple TV remote has a decent lifespan on a single CR2032 I'm sure it's IR emitter uses a fair amount of pulse current.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Bear in mind the pulse current should be supplied from the supply decoupling capacitor, not directly from the battery - as long as you have enough uF's across the battery, it should be fine.
 

rbairos

New Member
Thanks for the good points. My rough calculations suggested enough current used periodically to last several years, though Id be happy for one year usage.

The current will be drawn through a PIC output line (rated maximum 15ma) which will be the only component directly fed from the battery source. So I can basically place a large cap in parallel with the supply lines, which will allow it to fill at leisure, and be drained as requested?

Will the capacitor naturally leak causing the battery to prematurely empty?

Thanks,
Rob.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Will the capacitor naturally leak causing the battery to prematurely empty?

It's how all IR remote controls work - and it's what makes the batteries last a long time, even though the IR LED's are driven with an amp or so of current.

The batteries simply charge the capacitor, and the capacitor feeds the LED.

Leakage isn't a problem, although you could always try and source a low leakage capacitor?.
 

crutschow

Well-Known Member
Most Helpful Member
You can use a tantalum capacitor instead of an electrolytic to minimize capacitor leakage.
I know I'm being picky, but a tantalum capacitor is also an electrolytic type. It's common to use the term electrolytic cap as referring only to the aluminum variety, but tantalum caps have a similar method of generating capacitance, they just use a different metal. A new type of electrolytic that's now available from some manufacturers is made from Niobium Oxide. It's similar to tantalum but has some advantages, including potential lower cost.
 

audioguru

Well-Known Member
Most Helpful Member
Energizer Battery Company has a datasheet on their CR2032 lithium coin cell battery.
It shows the voltage dropping when a 6.8mA pulse occurs for 2 seconds 12 times a day.
The tiny battery cell is dead pretty soon.
 

rbairos

New Member
Bear in mind the pulse current should be supplied from the supply decoupling capacitor, not directly from the battery - as long as you have enough uF's across the battery, it should be fine.

So... If a 1Farad cap can drive 1 amp-second for 1 volt,
Am I correct in assuming, that I would need:

0.1 seconds
3 volts
15 milliAmps

= 4.5 / 1000 Farad ( 4,500 uFarad Cap) to do the job?

That seems huge for such a small application...
Would it simply be a matter of adding such a cap in parallel with the battery
power leads?
Is polarized/non-polarized an issue?


Sorry for all the questions, I've been searching with little luck,
on a capacitor driven circuit..

Thanks very much,
Rob.
 
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