I commute daily with a Light and Motion Seca 400. I ride predominantly at night (early mornings and late nights) and the speed and traffic of my commute dictates that I use a high powered light like the Seca 400, not a smaller LED light (e.g. PB Blaze).
My light and motion battery died a couple months ago , which sucks because those things are $120 to replace. I got just over a year of use out of the battery, which was over the warranty, so they won't replace it. If this is a pattern, I'm not excited about spending $120 a year on a new battery.
I did a little research and found out that the depth of discharge on Li-ion batteries really affects the life of the battery. I had been using the light daily, charging it weekly after the battery ran out, so I guess that explains why my battery died so quickly.
I just bought a $160 6-cell battery (deep discount) designed for the higher output models (greater capacity) with the intent of charging after each use, and using the low power setting to minimize the depth of discharge as much as possible. I'm not sure how long this one will last, but without doing any research on this specifically I'm hoping it will be 3-5 years.
I've also been looking into dynamo's a little bit, and they seem pretty enticing, mostly in the low maitainence, no charging and always available. I'm not too concerned about rolling resistance.
My goal is cost savings over the long term, with a secondary goals of initial cost, effort to install and routine maintainence.
My question is: will the battery last long enough and be little hassle enough to be worth the $160 I just dropped, or for a comparable cost and difficulty with installation, will a dynamo be better for this task?
I know there are a lot of dynamo advocates on here, so if you have a specific set-up or system you recommend, I'd like to hear that as well.