powering youre led's

[wildwood]

This isnt a plug, but like you guys building all youre lights I concentrate on the battery side of the lights

I was just looking ahead to see what you will be running youre lights on this year?

General feeling is either the 2 cell 7.5V or 4 cell 15V Li-Ion? are many of you looking at the 3 cell 11.25V?
Thanks in advance :thanks:

 

[Momato]

8 cell, 14.8 V Li-Ion on my part

 

[HEY HEY ITS HENDO]

Hey wildwood, ever considered or put a battery pack inside a seatpole?

 

[chris_m]

Personally I'm using a 4 cell 14.8V LiIon (not sure where you got your 3.75V rating from). That's with a buck driving 3 LEDs - considering using the same pack to power a twin MC-E with a boost (higher voltage might work better for that, but my charger only goes up to 4 cells).

 

[chris_m]

Personally I'm using a 4 cell 14.8V LiIon (not sure where you got your 3.75V rating from). That's with a buck driving 3 LEDs - considering using the same pack to power a twin MC-E with a boost (higher voltage might work better for that, but my charger only goes up to 4 cells).

 

[HEY HEY ITS HENDO]

chris, have you measured the voltage of your 4 cell pack when its fully charged? ... it will be over 16v !!

 

[leew]

14.8v 8 cell (4s/2p) Li-Ion here

 

[chris_m]

chris, have you measured the voltage of your 4 cell pack when its fully charged? ... it will be over 16v !!

Yes - charged to 16.8V nominal, but it settles at about 16.65V when taken off the charger. Your point is?

 

[Hack On Wheels]

Personally I'm using a 4 cell 14.8V LiIon (not sure where you got your 3.75V rating from). That's with a buck driving 3 LEDs - considering using the same pack to power a twin MC-E with a boost (higher voltage might work better for that, but my charger only goes up to 4 cells).

Yeah, I'm in the same boat. Right now I have a 14.8V Li-Ion for a triple with a bFlex, but I would like to be able to use that battery, or a smaller 14.8V to power a twin MC-E... not sure what the best way to configure that would be. What driver(s) are you looking at using?

 

[RGB_LED]

I have two 14.8v 4-cell packs for running my main headlamp which has a b-flex, triple SSC-P4, one 7.4v 2-cell pack and one 6xAA pack for twin Q5 lights.

HHIH, to your comment, my 14.8v packs are about 16.4v fresh off the charger, ie. charger light turns green. Lately, I've been trying to charge to just under 16v but it's sometimes difficult to monitor the charge process. Also, the 7.4v pack comes off my other charger at 8.4v. I suspect you may be hinting at something... perhaps that consistently charging above the nominal level, while giving more runtimes, pushes the LED harder or that it reduces the life of the battery...?

 

[chris_m]

Yeah, I'm in the same boat. Right now I have a 14.8V Li-Ion for a triple with a bFlex, but I would like to be able to use that battery, or a smaller 14.8V to power a twin MC-E... not sure what the best way to configure that would be. What driver(s) are you looking at using?

A modded Maxflex

 

[Hack On Wheels]

A modded Maxflex

Nice! Care to share the details? I looked at a Maxflex briefly, but I believe they are only supposed to output up to 24V, right? I'm assuming your modding will let it work for 28V? At the moment the only thing I can think of for myself is running each of the two MC-Es from its own bFlex, and have them each wired 2s2p, so the bFlex can buck down to ~7V for output... but that is pricey because of needing two drivers, and the wiring/soldering would/will be a pain. It would also leave me only able to drive them at 500mA per die max, but that is all I would want to do anyways. 700mA would likely make for too much heat to deal with easily.

 

[chris_m]

Nice! Care to share the details? I looked at a Maxflex briefly, but I believe they are only supposed to output up to 24V, right? I'm assuming your modding will let it work for 28V? At the moment the only thing I can think of for myself is running each of the two MC-Es from its own bFlex, and have them each wired 2s2p, so the bFlex can buck down to ~7V for output... but that is pricey because of needing two drivers, and the wiring/soldering would/will be a pain. It would also leave me only able to drive them at 500mA per die max, but that is all I would want to do anyways. 700mA would likely make for too much heat to deal with easily.

I've discussed it a bit over at the Taskled forum (Maxflex section). In brief it involves changing the resistor which sets the limiting voltage for the converter chip, and also changing the output cap for a higher rated one, since the original is only rated at 25V. As long as they've not changed the spec with the latest boards, the diode is rated at 30V, which would be the new limit if I change the cap for the 35V ones I've got.

However I may just end up rolling my own converter board - I have all the bits I need - just need to make a PCB.

 

[Hack On Wheels]

I've discussed it a bit over at the Taskled forum (Maxflex section). In brief it involves changing the resistor which sets the limiting voltage for the converter chip, and also changing the output cap for a higher rated one, since the original is only rated at 25V. As long as they've not changed the spec with the latest boards, the diode is rated at 30V, which would be the new limit if I change the cap for the 35V ones I've got.

However I may just end up rolling my own converter board - I have all the bits I need - just need to make a PCB.

Awesome, sounds good! So I would need to change the resistor, any idea what is currently on there? The diode would be good for what I want, and then I just would have to swap for a 30V or so cap. I just need it to work for 25.6 (best case, if each MC-E die is 3.2Vf), and for up to 28V (worst case, if each die is 3.5Vf). So 30V is probably the next rating up for parts. Hopefully I can find parts with the right ratings and the right sizing locally...

I'd be interested to know more about the process and all if you make your own board. I think that is a bit beyond what would be reasonable for me at the moment.