Estimating remaining life of save batteries by voltage?

Is this possible, to some degree at least? For instance, I measured a couple SNES and N64 batteries with 1995-1999 dates at around 3.07-3.08V. Is there any kind of cutoff point where it's expected to lose the data?

Interestingly enough I also have a Metroid 2 with 92-01 marking on the battery and that one has the highest voltage of the ones I tested at 3.27V.

 

can you look up the data sheet for the memory

 

My Ocarina of Time has a Sharp LH52V246A in it - Google comes up with some similar chips, but not this exact one, so I'm not sure how comparable the others really are. That Metroid 2 cart has a LH5168NFB-10L, I found a datasheet for what seems to be the same family of chips: http://html.alldatasheet.com/html-pdf/112558/SHARP/LH5168N-10L/154/1/LH5168N-10L.html

 

Not possible due to how Lithium batteries work (talking primary batteries aka disposable ones):

When they're depleted they actually deliver less and less current, they keep the voltage until they're almost 100% depleted which means the voltage will fall very fast and very near the absolute end of life.

 

There's a way to test in the datasheets. Short battery with 100ohm resistor for 2 seconds, then monitor how fast the voltage goes back up.

But it means removing from cart and losing save anyway.

So basically, just replace them every 5-10 years to be safe.

 

Thanks for this, good sir. I'll keep this useful information in mind for when I need to test these batteries.

 

No problem, basically attach multimeter to both terminals of battery, short with resistor. Voltage shouldnt drop below 2.6 (approx - may vary by brand) and should recover to approx 3v within a second or so.

Drops below ~2.5v = replace
takes long time to recover = replace

To use the full capacity, the voltage gets down to around 2v. But like you said, its like a cliff. Once its dropping below ~2.5v its not long for this world.

But again, only useful out of circuit.

 

Is there non volatile memory compatible with these carts?
I know there is some compatible with the save packs for n64

 

You could potentially use FeRAM I think but doing so makes no sense. Just use a device to backup your save data from the cartridge, then replace the battery and restore your data. It's not a big deal.