50g Backup Battery

[matalog]

I'm pretty sure that I changed the reserve battery in a 50g 3 months ago. Then I took out any AA batteries, and yesterday went to use it, and it asked to try to recover the old data, which it failed to do.

Does that mean that the 3 months completely drained the backup battery and I need to replace it again?

[Dave Frederickson]

Three months ago you replaced the backup battery and removed the main batteries. Then yesterday you replaced the main batteries and it failed to recover the old data.

According to the User's Guide the backup battery maintains the volatile memory while the main batteries are being changed and is intended to be used sparingly, not as the primary power source for the volatile memory while the calculator is in storage. So, yes, you need to change the coin cell again.

My recommendation if you are not going to use the calculator for an extended period of time is to backup your data then remove all the batteries.

Dave

[Vtile]

Yes the above. The backup battery circuit is extremely simple what I can remember... IIRC it was parallel with main batteries, not separate island powering memory chips (if any) only.

I suggest to use good quality modern "ready to use" NiMH cells, in your device if it is not a daily user. Those should be less prone to leakage than alkaline cells (which always leak when they are fully empty and chemicals start to eat the seals and body).