Reduce / Reuse / Recycle
I made the decision a number of years ago to only use rechargeable batteries whenever possible, as it made sense in two fundamental ways: 1. It's cheaper and 2. It's far better for the planet (but for those of who don't hold with this "hippy shit green ethos", please see point 1). The only downside that I can see is that it does involve a little bit more work and management on my behalf, as the rechargeables that I use do require a small amount of maintenance to get the best from them, and they have to be charged after use: but at the end of the day, I really don't see it as any additional hassle to be honest.
I have four different portable power sources that work together to give me various options to suit how I'm working: Sound Cart Battery (not discussed here), NP1 (Style) for the Handbag, PP3s (Radio Mic Transmitters) and AA's (Comms and Timecode).
Hawkwoods kit: it's robust and it's reliable. Admittedly, the initial outlay is expensive - but I don't regret it and you get what you pay for in my experience. I have four of the NP65 Lithium Polymer Batteries, which I judged to give me the best power / pound ratio. With my Sound Devices 788 and my 2 Micron DDH3 racks, I find I can use up to three on a long day with lots of channels - and I have the forth battery as a "spare". With these, I use the NPU-SQN4S regulated shoe, that can step down the output voltage to 9V if necessary. As for the charger - the 4 way MR4 was the only way to go. All four batteries can be put in at night, and all four will be charged by the morning. Not only that though, this charger can be used in a car from the lighter socket, and power a 4 pin XLR cart from the mains if necessary. Incredibly versatile.
AA and PP3
On a drama, I can easily eat my way through 20 AA on a normal day, for Timecode Boxes, Comms for directors / script supervisors / Execs / AD's, so having a reliable source of rechargable AA batteries is a absolute must. I've always been a fan of the Ansmann AA batteries that come with a 2 year guarantee, offering up to 2850 mAh, and always finding them to last through a days work. The slight downside is that as they get older, they don't hold their charge so well in storage. So in the past 6 months I've swapped over to the low self discharge type, the maxE 2500mAh. These style of batteries don't loose their charge (in storage) anywhere near as quickly as the conventional Ansmanns - and they are bloody brilliant. On the last long running drama, we only had to replace one set of comms batteries, and that was right at the end of an extended day that over - ran! The Ansmann Energy 16 charger, is great too - 12 AA batteries in one hit - and it conditions them as well.
I also have to mention my supplier - Tantronics. Fantastic support and customer service - giving 3 year guarantee on Ansman and Maha AA battery chargers.
As I said, hardly a thrilling blog topic. But something I wish I'd known 5 years ago.