Replacing lithium coin battery with a standard AA

[ag3n7]

Hi folks,
I have a device that takes a lithium coin battery that dies pretty quickly based on using the device so much.
I wanted to experiment by soldering wires to the contact of the device where the battery would go (positive and negative contacts) and connect it (pos and neg contacts) to a regular AA battery with resistors in between them to give out the necessary voltage of 3V.
Why do I want to do this? Because AA batteries are cheaper, easier to swap, and I think would last longer.
I tested the output with my multimeter and it does show an output of 3V after soldering the resistors to the AA battery, yeah....perfect right? When I solder it to my device, it does not work. So I am confused as to what is wrong. Did I miss a step?
Thanks in advance!

 

[(*steve*)]

What is "the device" -- It may not matter, but it might be useful information.

You will need 2 AA batteries, as they are 1.5V each. No resistors should be required.

Connect the batteries in series.

Remember that button cells have a polarity exactly the opposite to what you might expect. The body is +ve and the button on top is -ve.

 

[ChosunOne]

Yeah, what Steve said....I hope you didn't already reverse the polarity on"the device". Depending on what it is, you may have killed it.

If it came with a Li coin battery, I'm guessing it's a small device. Soldering battery lead wires on small devices can be tricky: Very easy to overheat any semiconductor parts near the battery terminals. I've done a lot of battery-substitution jacklegging and I recommend, instead of soldering, use wires soldered to a couple of small flat metal pieces sandwiching an insulator wafer so the whole assembly fits into the existing battery compartment. I've used aluminum foil, copper leaf, I've even used parts of disassembled batteries, with a wafer of rubber, plastic (expired credit card), even short lengths of wood dowel to press connections in 1/2 AA battery holders. That leaves it available if I want to go back to the original design battery too.

 

[jerryg50]

Substituting a 3.6 Volt Lithium

You would require two AA batteries in series. Most of these lithium types are 3.6 Volts. Some are 3.2 Volts depending on the type. Two AA batteries in series with no load should read about 3.2 to about 3.6 Volts. The two in series average nominal voltage under rated load should be 3.0 Volts.

You can get a battery holder that can hold two AA batteries in series. Most any electronics parts supply can have this for you.

You then simply wire it in to where the power is supposed to go on your circuit board. You will not need any series resistor because the voltage will be extremely close. Be very careful to not get the polarity wrong. The circuit board may not have protection for wrong polarity.

To save space you can also consider to get a AAA battery holder and use AAA batteries. They will be a little smaller, and probably last very close to that of the AA batteries.


Jerry G.

Hi folks,
I have a device that takes a lithium coin battery that dies pretty quickly based on using the device so much.
I wanted to experiment by soldering wires to the contact of the device where the battery would go (positive and negative contacts) and connect it (pos and neg contacts) to a regular AA battery with resistors in between them to give out the necessary voltage of 3V.
Why do I want to do this? Because AA batteries are cheaper, easier to swap, and I think would last longer.
I tested the output with my multimeter and it does show an output of 3V after soldering the resistors to the AA battery, yeah....perfect right? When I solder it to my device, it does not work. So I am confused as to what is wrong. Did I miss a step?
Thanks in advance!