3V lithium battery physics

[dinnerpianist]

A Boss drum box I've had for ten years finally gave me message of memory battery low. No complaints- I put in a new battery. The so called "spent" battery read 2.84V with a good tester. I was under the impression that maybe it would have to drop to 2 or so volts to trigger a warning.

 

[blistard]

Maybe, if you measure it under load the voltage will sag?

 

[dinnerpianist]

Hadn't thought of that. Should I have the AC adaptor connected when I do a reading? Is there any danger of putting leads onto that button battery holder while the unit is powered?

 

[metalsculptor]

A battery expected to last 10 years will have very little load in normal use. It may be a 3.7V lithium battery.

 

[dinnerpianist]

battery load and replacement

The BOSS DR670 drum unit uses a typical CR 2032. The owner's manual said six years was to be expected. I've had early Yamaha FM modules where the battery lasted 12 years. I'd get scrambled lettering on the custom patches read out to inform me that the battery was struggling.

 

[macboy]

Just load the battery with a resistor. In this case, around 1 kΩ would be OK, that would provide a nominal load current of 3 mA. Measure the voltage while the battery is loaded. If it is spent, it will become obvious. Most batteries will provide a voltage reading near nominal even when nearly completely spent, if left without a load for a while.

 

[yajnaS]

that would provide a nominal load current of 3 mA.

3mA is actually the upper limit for a CR2032. The standard discharge current is 0.2mA.

http://www.panasonic.com/industrial/includes/pdf/Panasonic_Lithium_CR2032_CR2330.pdf

 

[Triodethom]

Then some thing in the 15k range would be the proper load ?

 

[dinnerpianist]

Thanks fellows but you are already over my head. I did do the preemptive thing a few years back and put in button battery holders in about twenty programmable units so I could swap out the battery easily and quickly. That procedure was plain awful, pulling out circuit boards so I could remove the deeply embedded soldered battery and then finding a proper place for the new battery holder.