Battery testers

If you are walking in winter and coming down late off the mountains you really do want to know that the batteries in your head torch are all good and that there isn't a duff'un going to fail after five minute use. But for photo use no it isn't so critical, just buying reasonable batteries and charger then getting on with taking pictures rather than worrying about batteries is not a bad approach.

I'd take the fresh pack of lithium primaries out of my bag and have them warm in my pocket ready I wouldn't be relying on rechargeables.

You could charge your batteries and keep fit at the same time if you adapt your charger to fit on one of those Australian pedal driven dynamos you see being used to power the radio in old movies

For fans of eneloops, there's only one way to test a battery - the eneloopy.


http://www.eneloop.info/eneloop-products/accessories.html

The colour of the dog's nose indicates the charge level!

Explanation of how to use the dishes and bones here and what the nose colour means:

http://www.hardwaresphere.com/2010/01/26/eneloopy-battery-checker-is-snoopy-on-camouflage/

For that purpose I won't rely on any battery I haven't tested and measured. So any single use battery out of the pack is a no go.

I guess If you don't have an aversion to superfluous weight and junk you could have some extra's along just in case one was faulty. Trouble is that even then you don't want to ever take partially depleted batteries along as it's difficult to know how much life they have left so you end up just using them once and always chucking them away long before their life is up so non-rechargeable batteries really aren't practical. And bad karma

I just bought the Chipmunk BL-500 from BatteryLogic
Cheap as chips and currently evening out all my eneloops with it's individual charging and LED levels display. Discovered that some of the batteries in my well charged packs of 4 are actually nearly flat.
Comes with a car adapter for charging in the field. It's Ace!