Cache battery that will charge and provide power?

[Mark E]

Does anyone have a recommendation for a battery I can use between my sp hub and garmin to act as a cache. I want it to take power from the hub whilst powering the garmin, thus preserving the Garmin's internal battery for night riding when I'll switch the hub power to the light. There seem to be loads of batteries around, however not all of them seem to charge and give power simultaneously. Has anyone come across a particularly effective one?
Cheers
Mark

[johnnystorm]

Have a look here:
http://bearbonesbikepacking.co.uk/phpBB ... 9&start=50

[Mark E]

Thanks, I knew I'd seen it somewhere on here earlier in the week, but couldn't remember where!
Mark