I have a push button gun vault that quickly goes through batteries. I tried some rechargeable 9 v lithium with mixed results. It seems that acceptable voltages for fully charged batteries are 8.4 volts. It was hit or miss to find one that measures 9.15 when charged. Something to be aware of if anyone goes down this path.

If these fail, it will be a power supply or battery tray

Lithium ion or NiMH?

NiMH 9 volts are often a little lower voltage than alkaline, but can supply plenty of current, so in voltage-tolerant applications they usually work fine (although charge indicators tend to read low). In applications like your safe, you would need to be careful to get low-self-discharge NiMH batteries - standard NiMHs will drain in a few months even if they aren’t powering anything.


I wasn’t aware lithium ion 9V batteries existed, the nominal voltage of a 2 cell Li-ion is 7.2V and of a 3 cell is 10.8V. In theory that can be managed with internal circuitry in the battery, but I haven’t seen it done with 9Vs.

I have one of those little drawer safes with the pushbuttons that use 9V batteries. I agree the Alkalines don't last long.

So, I use these primary (non-rechargable) 9V Lithium Metal batteries.
https://www.amazon.com/Energiz.../ref=dp_ob_title_hpc

under normal use, they last about 8 to 10 months which is good enough for me.

I measured the voltage on them a few years ago, and I don't recall the exact voltage, but it was nothing shocking.


---yes, that last word was intended as a pun

I use normal 9v, glad this came up, probably should change mine...