John's homebrew pages
NiMH battery pack
One of the things about portable operating is the weight of the batteries you end up carrying.Until now I have always carried SLABs (sealed lead-acid - i.e. heavy - batteries) up the hill, and will continue to do so especially for contests. However, for lightweight SOTA expeditions I have used just the bare FT-817. Unfortunately it holds only 8 NiMH (nickel metal hydride) batteries, which give a lowish voltage and hence reduced power. Ten of these things up the voltage to 12V and allow "full" power operation - more or less.
Here is a 10 cell battery pack (Maplin) made up with an Anderson Powerpole connector. The Velcro strap is to stop them falling out in the rucsac, and the PVC tape insulates all the metal bits. It's carried in a plastic bag for extra security. The cells are, of course, charged out of the pack in a separate specialised charger.
The first experiment with this as an external supply for the FT-817 was reasonably successful; the rig only indicates reduced power occasionally, during very long transmit overs using SSB. I don't think full power FM would be a very good idea with this though.However, I will try using a couple of packs for the small linear which doesn't have a huge power consumption at 24V, just to see if they work for that application as well.