Optimum voltage for LAs?

[SpiritLed]

Is it worth the effort to run a 9v lamp on two 3.7v cells (with regard to brightness and color)?

I have read some WE (Rattlesnake) posts listing the options for using various lamp and battery combinations:

380 lumens 9V Lumens Factory HO-9L (2 x 18650) 7.4v
400 lumens 13V Lumens Factory HO-13L (3 x 18650) 11.1v
700 lumens 13V Lumens Factory EO-13L (3 x 18650) 11.1v

Sounds like these work well by the comments, but they appear under powered.
How much under voltage is too little and how much over is it advisable to go?

 

[jsr]

A 9V bulb isn't really 9V. It's actually about 7.2V-7.4V, so running 2x 3.7V cells is perfect. A 6V bulb is really about 4.8V-5.4V. The voltage they place on the bulbs' labels aren't actually the voltage they're designed to run at. That's just easy for people to understand since the bulbs are made for primary 3V batteries, so people know a 6V bulb needs 2x primary 3V cells and a 9V bulb needs 3x primary 3V cells. In reality, a primary cell drops in voltage (voltage sag) when it is loaded and must supply current. How much sag depends on the how much current, but most 3V primary cells range in the 2.4V to 2.8V range when loaded (lower voltage the more heavily it is loaded). So a "6V" bulb that's actually a 7.2V bulb runs fine and within spec when the 2x 3V cells drop to about 2.4V-2.6V each. Hope that made sense.

 

[SpiritLed]

Thanks for the "practical lamp" lesson jsr.

(Quote)
So a "6V" bulb that's actually a 7.2V bulb
A 9V bulb isn't really 9V. It's actually about 7.2V-7.4V
(End Quote)

So, using rechargables:
1) 3.7 cell for 4 volt lamp
2) 3.7 cells for 6v or 9v lamp
3) 3.7 cells for 12v or 13v lamp

Is this correct?
Better to ask than flash!

 

[Mark@LF]

SpiritLed,

If you want to use rechargeables, then:

1 x 3.7 cell for 4V
2 x 3.7V cell for 9V
3 x 3.7V cell for 13V

Do NOT use 2 x 3.7V cell on a 6V (any brand)
Do NOT use 3 x 3.7V cell on a 12V (at least for OUR LAs)

Thanks

 

[SpiritLed]

Thank you Mark !!

Doesn't get any clearer than that.

I feel a strong desire to visit LumensFactory

:twothumbs

 

[jsr]

Spiritled: oops, sorry, I meant to say the following:

"So a "6V" bulb that's actually a 4.8V bulb runs fine and within spec when the 2x 3V cells drop to about 2.4V-2.6V each."

You can also run a 6V bulb off 2x 3V R123As fine.