Which batteries for an Ultra-Marathon
... just some remarks on equipment
I recently had the chance to run the JUNUT 230k. A non-stop Ultra-Trail run on the "Premium Wanderweg" Jurasteig.
Total Distance was about 230k (237km measured by my Forerunner 305) time limit was 52h. The race starts at 10am in the morning and I was hoping to reach the finish line within the next two days (<=48h).
Speaking two days equals two nights out there running on sometimes really rough terrain so it was not really easy to decide on what to put in the running pack and into three drop-bags.
I could write much more on equipment and the race by itself but for now I stick to the topic ...
Besides my old Forerunner 305, which was charged via an external battery pack during the run, I took along a Garmin eTrex merely as a backup. My head lamp is a Petzl MYO RXP which, most of the time was at level 5 (I have programmed settings 8, 5, and 3 ... (I guess)). What I don't like about the MYO RXP is that after you have set one lightning mode you cannot switch modes without the lamp turning off :( But besides that this one is excellent and probably one of the best if you look at the price-value tag.
I had one more electronic device which was my LG-E610, this is for emergency calls and taking some snapshots, so no need to worry about battery life during 48 hours.
So I had to make sure the eTrex30 and the Petzl will run long enough for this run. Sure the usual approach is to buy standard cells and take spare batteries in the pack during the run and keep some in the drop-bags. Or use rechargeable cells and keep (usually) even more replacement batteries around.
This time I thought I give Lithium non-rechargeable standard AA cells a try. Sure they come at a little higher cost than alkaline but in turn they have higher capacity and are very light.
After the run I can really recommend on the Energizer Ultimate Lithium which have a specified capacity of 3000mAh. Using three of them in the MYO RXP at an average lightning mode allowed for operating the lamp for full two nights without any noticeable performance loss (same intensity of light).
The eTrex30 was also running on two Energizer Ultimate Lithium and was fully operational after the 48h. I have to admit however that I had no need to change zoom-level very often or otherwise turn on the backlight (navigation was mainly done via the Forerunner 305 which is much more comfortable, while wearing the watch on the wrist).