rule the night
I just put new batteries for my lights on my bike this weekend. I use sealed lead-acid batteries because they're relatively cheap and fairly tolerant of how they're recharged. But the batteries do have a finite life, and their life is shortened by deep discharge cycles. When I use them in pairs, they tend to last me for 3 or 4 years of commuting. The last pair started getting feeble back in the spring, but after the choir rehearsals stopped for the summer I wasn't doing much night riding. With the longer summer days I was usually home from work before dark. But with the switch back to standard time this weekend I'll be riding home in the dark more often than not, and choir rehearsals will add more night riding after that. It's nice to have my lights bright again.
I got the batteries for $11 each on the web, which is half what I paid for them in a local store last time. Shipping ate up half that savings, but I still came out ahead (and I didn't have to go get them). The big surprise was that they came FedEx.
Next, I'm thinking about upgrading from halogen to High Intensity Discharge lights. HIDs are the bluish-tinged lights that have become common on high-end cars. They're about 3 times as efficient as halogens, so I can have light for much longer (fewer deep-discharge cycles) or carry fewer (or smaller) batteries.