I use lithium iron phosphate (LiFePO 4) batteries for my Summit On The Air Activations, any any time I’m operating portable really with my Yaesu FT-817 or FT-897D. They give reliable power for a long period of time and crucially for me – don’t tend to explode as much as LiPo batteries! (search youtube for ‘LiPo explosion’ !)

They do however need a special charger – you cant just plug these into the charger you use for you NiMh AA’s. Unfortunately there are a lot of options for chargers out there, the majority of which on ebay etc. seem to be clones. Now I don’t mind buying clones of some products, but for things that are liable to lead to a fire if they fail I’d rather stick to branded originals. And the charger that I was advised to get and I’m still happy with is the SKYRC iMAX B6.