Badboy input voltage concern using 4.2v Li batt.

[moraino]

I am thinking of using Badboy for my new mod, the ASP with LS 3watt powered by 18650 Lithium. I want high ppower with flat curv.

The maximum voltage will be 4.2 volt. I am wondering if it is ok to run the Badboy at that voltage. It seems somewhere I read that the input voltage should not be higher than the LS Vf.

I know of a 1W stepup converter will run direct drive if the input voltage is higher than the Vf. Does Badboy operates the same way? If not which converter should I choose. Thanks for the inputs.

Henry

Ooops, I post this at the wrong group. Please move me to the Sandwich Shop. Sorry for the trouble.

 

[Chop]

moraino,

I've used many of the version 4 badboys to build lights to run on Pila li-ion batts. I've had no problems using luxeons with J and K Vf's, but I'd stick with the K's to be safe. It seems that the revision 4 badboys are a bit forgiving and the voltage drop of the batt helps a bit too.

I'm no electronics guru, I only stumbled upon this when I discovered that my lights with downboy circuits in them would not run in regulation on a Pila. I figured that if it didn't work with a downboy, a badboy must be in order.

 

[Klaus]

Tony,

using Arcmanias modified Downboy and very low Vf LEDs the combo is working perfectly fine, in general I agree that BBs should be working better. I still would *think* that overdriving the LED (even less than in DD due to the diodes Voltage drop) is the only real danger - I´m not sure that the badboy circuit or IC would get damaged after all - did Wayne ever say so ?I think the concerns were more with overdriving and frying the LED but I might be wrong - I would like the master to chim in as well and clarify but I guess he´s busy sourcing new LEDs and working on the nextgen badboy /ubbthreads/images/graemlins/grin.gif

What might be considered is that with a Badbody the bare LiIon will get drained well below the danger zone when the user is not properly taking care - with a Downboy this is taken care off by the LED and its characteristic itself (as stated above - makes sense only when the DB is modified and the LEDs VF is very low - both seems to be very hard to get by parts though). Tradeoffs everywhere /ubbthreads/images/graemlins/crazy.gif

Klaus

 

[Doug S]

[ QUOTE ]
Klaus said:
Tony,

using Arcmanias modified Downboy and very low Vf LEDs the combo is working perfectly fine, in general I agree that BBs should be working better. I still would *think* that overdriving the LED (even less than in DD due to the diodes Voltage drop) is the only real danger - I´m not sure that the badboy circuit or IC would get damaged after all - did Wayne ever say so ?I think the concerns were more with overdriving and frying the LED but I might be wrong - I would like the master to chim in as well and clarify but I guess he´s busy sourcing new LEDs and working on the nextgen badboy /ubbthreads/images/graemlins/grin.gif

What might be considered is that with a Badbody the bare LiIon will get drained well below the danger zone when the user is not properly taking care - with a Downboy this is taken care off by the LED and its characteristic itself (as stated above - makes sense only when the DB is modified and the LEDs VF is very low - both seems to be very hard to get by parts though). Tradeoffs everywhere /ubbthreads/images/graemlins/crazy.gif

Klaus

[/ QUOTE ]

Klaus, you pretty much have it right on all counts. Your caution about overdischarging Li-ions is especially important and one that seems to be overlooked by those considering Li-ion plus stepup converters. I can think of one scenario by which a BB *theoretically* could be damaged by a Li-ion + BB combo but it is likely only theoretical. The scenario is that of a fully charged cell with a very low Vf LED. The resulting current through the BB diode could conceivably be as high as several amps. The diode is likely a 1A rated part so it could be operating in excess of it's specification.

 

[Klaus]

Doug,

you are certainly right, I was talking from more or less standard VF parts which I found to be working not too much in overdrive in ARCs with the rev2 circuit which is quite similar to the badboy and where the diodes voltage drop resulted in even lower than LiIon DD currents well below 1A - but using a low Vf part could well result in the problems you describe and blow the diode or more.

Thanks for clarification

Klaus