Originally Posted by 01 CAt Man Do
I'm a little confused; What is being powered by the 4-cell battery pack, the GPS?
I would think the battery pack would last more than two hours but if the working voltage on the GPS is greater than 6volts that would help explain things.
Some tips: Cheap torch holders are available from any Chinese web sites and work very well. Back in the day when the first LED torches were coming out I use to just use an old Marwi bar mount as a platform, sit the torch on that and use rubberized hair bands to keep it in place ( DiNotte style ). Worked very well with the smaller torches but a dedicated torch holder is better.
It's actually a 6 cell battery (it's double sided and has 8 cell spots) with 2 of the cells spots shorted that are wired to the flashlight which has a 5 D-Cell bulb in it. The standard 2 cell bulbs are bright enough to be seen, but not bright enough to be able to see the road conditions.
I tried the Chinese made flashlights and they are really unreliable and not nearly as bright. The bulb I put in the flashlight is a Magstar 5 Cell Xenon bulb 5.5 watts 150 lumens 3100k. The reason I am using 6 cells on a 5 cell bulb is that 5D cells is 7.5V and 6 NIMH cells are 7.2V. Now, obviously, a 5 cell flashlight bulb can run on as low as 5V (Alkaline cells are considered dead when their voltage drops below 1V), but that tends to draw higher amperage which would more likely to overheat the element and shorten the life of the bulb.
The GPS is just using 2 standard rechargeable AA batteries that fit inside the unit. My LBS had a device that was designed for phones that would mount the GPS just fine, but they wanted $30 for it, plus 8% sales tax.
When my bike rack comes, I am going to use 12 C NiCad cells to make a battery pack for the light. NiCad batteries love to be deeply discharged, have MUCH lower internal resistance and perform well under high load and I have dozens of them from a hobby I have and that would give me a 25 watt hour battery (2 sets of 6 in parallel). What's more, they are all well matched, so I don't have the problem of a single cell reversing on me.
Last edited by christo930; 02-16-13 at 02:27 PM.