battery

The Battery Saver is designed to prolong the battery life in small toys and devices by
disconnecting the load after a preset period. The two versions shown switch up to
one amp and give about one minute of operation before shutting off.
When the switch is pressed, the capacitor charges and the full battery voltage is applied
to the [...]

Mod a 9V rechargeable battery to give you +3.6V, Ground and -3.6V.
You will appreciate this idea if you ever had to clobber together a bunch of AAs or AAAs to get a project working.
This instructable was meant to be part of a larger project, but I decided to submit this part alone to the 9V [...]

I have a set of noise cancelling headphones at work. The active part does a nice job on the building ventilation and computer fans, and the passive part on my co-worker’s phone conversations. I didn’t like the idea of wasting batteries, though, and the system didn’t seem to like even NiMH rechargeables. So, I decided [...]