There is often a need for a 9V battery for portable test equipment (NNA, Noise Bridge, Low R meter, Power Meter etc). A solution is a 8 cell NiMH pack.
Above, a battery pack made from two Hobbyking 4 low self discharge AA cells. The packs come with JR servo connectors, and the pins are rewired to use the -ve from one pack and +ve from the other pack to one of the JR connectors. The other wires are connected via a 3A Polyswitch for s/c protection. A short JR to 2.1mm DC connector is made from a JR extension cable and 2.1mm connector.
The pack is wrapped by 50mm diameter clear heatshrink to make a single robust package.
The Polyswitch can become very hot if activated, so don’t tuck it under the heatshrink. A fuse could be used instead of the Polyswitch.
Both packs have been labelled with their correct voltage, the pics show the original labels to show the source of the component parts and of course, both packs are double the voltage of the component packs.
- 4.8V 4cell NiMH pack: 9169000006 ($6)
- 6.0V 5cell NiMH pack: 9169000008 ($7)
- Twisted JR servo extension: AM1043-30CM ($3/5)
The 3A Polyswitch is available on eBay.