Long lasting 3V battery for benchtop DMMs (3478A, 34970A, ...)

[hatte]

I have been looking for the optimal replacement 3V battery for benchtop multimeters for a while, and believe I have identified it.

The 3V batteries used in the HP/Agilent/Keysight typically have a shelf life of around 10 years, but as the batteries are soldered onto the PCB, it means that battery replacement is a non-trivial task – especially if you want to retain the calibration data which is kept alive by the battery on the 3478A.



You either have to replace the battery while the DMM is powered (using a non-grounded soldering iron), or you have to connect a temporary power source (battery) while unsoldering the old battery, and soldering in the new.



I recently discovered some attractive properties of the Energizer Ultimate Lithium AA battery:

• 25 year shelf life
• Guaranteed leak-proof
• 3500mAh capacity

Two of those batteries, placed in an AA battery holder with leads are easily fitted inside the enclosure with a couple of cable-ties.

The leads can be soldered to the existing 3V lithium battery PCB pads, after which the legs of the old battery can be cut.

Easy and low-risk replacement, and peace of mind for the next 25 years.

The most important part is to secure the battery pack

[adam4521]

I'm not so sure about the spring contacts. In the dank winter environment where I have to store some of my stuff, I'd prefer it soldered in. I'm pretty sure my 3478A is on it's original battery, so c. 40 years. It's documented on the forum how to backup and restore the calibration constants, which I've done, so as to not worry about it.

[audiotubes]

Would a CR123 (or the rechargeable version) work for you?

These are good batteries popular with the flashlight crowd.

[adam4521]

https://industrial.panasonic.com/cdbs/www-data/pdf/AAA4000/ast-ind-243194.pdf

[GigaJoe]

1.5 +1.5 =3.0 V
and 0.5 drop over diode .. let say 2.9 that an edge for memory storing data , as if i recall it correctly it 2.7-2.8V at bottom

that why you need 3.5V that in time it drops to 3.0 after 40y and still supply sufficient voltage 

[Nusa]

No leak guarantees don't mean the batteries never leak. It just means if you successfully make a claim on the guarantee you may get a refund on the value of your device. Read the guarantee if you want details.

Duracell alkaline cells, which are somewhat well known for leaking, also have a no leak guarantee. They just rely on 99% of us not willing to spend the time and effort to make a claim.

[Shonky]

I recently discovered some attractive properties of the Energizer Ultimate Lithium AA battery:

• 25 year shelf life
• Guaranteed leak-proof
• 3500mAh capacity

Two of those batteries, placed in an AA battery holder with leads are easily fitted inside the enclosure with a couple of cable-ties.

Note that these are about 1.8V open circuit voltage (which will be what your backup circuit sees) when new. So you'll be a bit over 3.6V when new.