Newbie Thinking of upgrading a Cateye

Hi first real post so please be gentle on me. I've already done a search and read about the modifications done to Cateye double and triple shot lights in here.

I now have a Hope R4 system and a Hope district rear light. The Hope system uses 7.4V LiIon pack rated at 5200mAh.

What I was wanting to try to achieve is upgrade the Cateye LEDs and purchase a LiIon pack to fit inside the Cateye battery bag. If I could run whatever I upgraded the Cateye to at the same voltage as the Hope system I would (hopefully) end up with interchangeable battery packs to use what lights I needed on any particular occasion.

Trout did a helluva job to a Triple shot http://www.candlepowerforums.com/vb/showthread.php?270295-1800-lumen-Cateye-Tripleshot, a good time back.

I just notice that 14.8 V systems seem to be the weapon of choice for a lot of the modifications.

If anybody has thoughts observation or general thoughts I'd be interested to hear them. I'm totally new to LEDs but have some understanding of electronics.

John

So what cateye are you going to upgrade ?
2 led @ 7,4V = buck driver
3 led @ 7,4V = boost driver

Hi Szemhazai

Thanks for the post.

I am wanting to upgrade a twin shot so I need a buck driver to lower the Voltage I guess. With the twin shot I'm guessing we are talking typical say 3 volts per LED in series giving 6 Volts.

I need to do research or get assistance on the LiPo characteristics as the Voltage is bound to drop as the battery discharges, but as yet I don't know how much charge I'd get out a 7.2 LiPo pack before I'd hit the 6 Volts barrier, not too much I'm guessing. I'm beginning to understand why going to 14.8V for a supply makes sense, that then does away with any worries of minimum Voltage as the battery discharges.

Would wiring each LED in series with a resistor and then paralleling them work with the Buck driver? My supply Voltage to the Cateye would then be a bit over 3 Volts giving me more headroom with the battery pack Voltage dropping as it discharges. Would that be a proposition or am I showing my ignorance.

Realize that those of you here a while will be fully conversant and be :shakehead. Appreciate if you don't flame me just yet.

John

Why you are going to waste some energy on resistor ??
2sXp Li-Ion's have 6-6,2V cut-off and 8,4-8,5V when fully charge - so it's a bit tricky to connect them in series from 2S power supply, especially on higher currents - if 350mA is enough for you (2x150 lumens from XP-G2) you can use BuckToot and it will works fine with efficiency reaching 93%.