Re: Fenix TK40 part2
The batteries are 2P4S, right? So each battery will see half this discharge current? Or am I mistaken?
Nevertheless, anything but lsd nihm would be a vaste in this light.
I guess they are 2P4S. As far as the discharge current per cell is concerned, however, it doesn't really matter whether they're 8S or 2P4S. Think about it this way: Fenix states 2h runtime in turbo. They likely tested this with batteries of at least 2000mAh (at least their L2D advertised runtimes were quite consistent with high-quality 2500mAh NiMHs). This means every battery has to be discharged at a current of 1000mA or more. By the way, 2P4S has half the voltage compared to 8S, so to deliver the same power, it needs twice the current. This current is then distributed over two separate battery series, so the current through each battery is the same in both cases.
I should note that 2P4S does have the advantage of lower battery pack resistance (by factor 4 actually!). This should improve runtime on alkalines somewhat as the percentage of power spent in the battery pack is roughly cut in half (remember power = resistance * current, so 1/4th the resistance times 2x the current means one half the power).
When only four batteries are inserted, the resistance is doubled compared to 2P4S, and each cell has to deliver twice the current. This is probably the reason why Fenix recommends that 8 batteries are used whenever possible, as you will get less than half the runtime on only 4, possibly much less. Anyone who plans to use alkaline batteries in this torch should definitely fill all slots.
I share your opinion about LSD rechargeables. For some uses, the roughly 40% higher runtime on freshly charged (and not too old) high-capacity NiMHs may be more important, but I'm basically sold on the convenience and longevity of the new cell type. :twothumbs
I've only started to test my new Eneloops (arrived this week), but the two Panasonic Infiniums I bought some weeks ago at the DIY store perform very well in my LD20, and unlike many of my traditional NiMH AAs, they don't get hot when quick-charged, only very slightly warm. :thumbsup:
I'm thinking others mite too. Pre-Orders mite be sending out on some stores today or Monday:bow:
