integrating circuit for charging and optional auxiliary supply




as the topic states, i'm looking to integrate a complete Li-ion charger into

a flashlight. Because this yet to build flashlight would be used every day

primarily as bike light, i don't need the fuss of endless disassembling and

recharging. I think, hooking the bike up to it's wall mount and just putting a

plug into the tail is a decent procedure. The light is going to be a single

XM-L, mayby slightly overdriven (max 3,5A). The new XM-L hits, as i see it,

some walls. Since i only want a single battery and 18650 proven to be on

edge and can't sustain 3A for more then a few minutes, i will probably go for

a 26650 IMR. The high current makes usual clicky switches a pain in the ***

an so i will use a MOSFET (or i opt for LFlex). My first choice on that

matter is the IRLR3717 with a drain to source resistance of 0,004Ohm and

gate threshold voltage ranging from 1,55V to 2,45V.

Second in row: IRLZ34N (R(ds)=0,035Ohm, V(gs)=1-2V).

Both are working well without any additional parts, btw.

I suppose a quick and dirty way would be to just wiring jack/plug to the output

of a Li-ion charger. But i would rather take a more sophisticated approach witch

provides more flexibility. A jack for a here in germany quite common

2,1mm round plug (Hohlstecker) and a charging circuit with an input voltage,

ranging from 5-12V (or 5V and powered by a LM7805 constand voltage regulator)

would very versatile and enable the use of a wide range of wall power supplies,

wich can be found almost anywhere. Only one cell to charge does not requiring

load balancing or some other fancy obstacles, so it should proven not to hard.

Because my bicycle is completely lawful, hence equipped with mandatory lighting,

wich is powered by a Shimano DH-3N80 hub dynamo. I read once, this dynamocan

easily provide 10W energy if the electrical restraints are removed. If i

calculate the energy requirements for the front Lumotec IQ Cyo senso plus and

the little red led rear light.... there should be at least 5W left over.

And yes... of course i would love to see that otherwise wasted potential fed

directly into the battery draining XM-L. Bottom line.... i need a ciruit that

will be able to recharge from a wide range of DC Voltage while the torch is

switched off as well as benefit from pluged in auxiliary sources if it is

lighten up.

Concerning the first goal, charging circuit... i'm not sure wich way to go.

There are a lot of highly integrated sophisticated special chips from Maxim or

Linear Technologie... on the other hand, a simple solution with discrete parts

like LM317T/LM350/L200/etc. might very well suffice. At this point, i can only

guess and any hint or advice would be appreciated.

On how to implement the auxiliary rail and the dynamo hub tweak.... i'm even

more in the dark and still more in the idea state. Any suggestion and ideas

here are most welcome as well.

... on a personal note:

As you can see i'm fresh flesh on CandlePowerForums. With electronic, i recently

revived a long abandoned interest and short after that, i got infected with the

flashlight virus. This community is great and as competent as i'm used to like

on the usenet/newsgroup, you know, back in the old days.....

There is an almost inexhaustible amount of information here, all very

interesting and relevant, which kinda constitutes a problem for a bloody

beginner like me. Even though i handle information like the Borg - by

assimilating it, preferbly entirely, i get absorbed by it.

But at some point, you actually have _to_ _do_, rather then read and learn

about it. Anyway... i startet about ten weeks ago out of frustration over

this one:

Plastic lens, plasic reflector, 3xAAA, only XR-E Q4, hence insufficient power.

Now it has a XM-L@4A driven by a single 32650 Li-Ion DCell, embedded in a decent

alu smooth reflector and not behind plastic, now the whole thing has grown into

what i call a flashlight.... :) After that i upgraded an old 3D Mag (weird

construction btw, looks like french engerneering....) with an SSC P7 and since

this point, i got addicted and i'm in the devils circle, more, bigger, brighter..

I guess there is still some inevitable collateral damage ahead of me, like

i destroyed four XP-G R5 emitter while figuring out a working method of reflow

soldering them. (in the end, the electric iron made it, btw)

I still have a lot of strange ideas that need to fail before i can settle

down, i guess. So... after the topic of this post is water under the bridge,

i will approach the tricky heat issue with ab bunch of heatpipes from countless

old nootbooks.

Greetings from Berlin