This is a Ray-O-Vac Hunter Lantern 398, purchased on eBay, new-in-box. The Texas Ace Calibrated Lumens Tube measured 20 lumens with original bulb.
It would have used a 6V lantern battery, back in the day. It can also use eight Ray-O-Vac "#2D" cells (according to the instructions). However, regular D cells were too big and C cells were too small. The Ray-O-Vac #2D cell must be something unique. Doesn't matter, I will use 21700 batteries.
An EBLCL Maglite LED bulb (link) was installed in the bulb holder, giving it about 130-150 lumens, measured out the front (see runtime graph). A blob of solder was added to the spring, for better contact.
A dual 21700 carrier was hot-glued and wired into the main housing.
Two Samsung 21700 were installed in series (the EBLCL Maglite bulb is rated up to 9V).
DC-Fix diffusion film was added to the front lens to smooth out the beam.
A runtime test was performed, to make sure everything is working.
That’s really cool, Terry. Awesome how it still looks stock (except for the film) and I’m assuming everything can be undone?
Also, does that bulb have low voltage protection? Based on the runtime graph I’m guessing so, but I’m not sure how that would work based on it handling 3-5 D batteries.
The cut off voltage is 2.5V. Just tested another EBLCL bulb on a variable power supply. At 2.6V - just a little bit of light - at 2.5V, nothing. I've used that bulb in about six other vintage lights, no problems.
Ohhh. I’m sure I don’t need to warn you of this but I’ll just throw it out there… be careful with that cutoff. With your cells in series, each one could get down to 1.25V
I’d be curious to see if the light is equally bright with only one cell (or with them in parallel for extra runtime). That way low voltage isn’t a concern. With such a wide voltage range and flat runtime graph, I’m curious if there’s a small stepdown circuit inside. In which case, running cells in series (higher voltage) actually might not increase brightness.
Just did an experiment with a power supply and the Texas Ace Tube. At 3.7V (approx one cell), output drops significantly (from two in series at approx 7.4V). Would only get worse as the single battery level drops a bit.
Thank you, the fw3a’s have a lexel boards in them. I made the one currently in the E01 from a Banggood lighted tail switch (cut it down, drilled the hole for the led, sanded the bottom down really thin).
I have a new design ordered from oshpark using a ring of 6 led’s with 2 additional red led’s that come on when voltage is low (main led’s go off and red come on at 3.08v) using a MAX809 voltage reset monitor. I only put that 2 led hacked up board in it today cause I had the driver out and wanted to go ahead and wire the aux leds up now for when my boards do come.
1.25 is best case scenario if the batteries are perfectly balanced, if not you could have one drop below that while the other is running fine at 3.6v for example. In series you’ll need to keep an eye on both batteries separately.
As you have the space and obv the modding skills you could maybe add a couple of protection circuits for an easier life.
Nice mod though! I’m a big fan of sleepers.