Lumapower Mentor advice needed

Just purchased a Lumapower Mentor MT-02 to deplete a large stockpile of C cells left over from led lighting from our wedding decorations (we had to dress a barn and each set of white lights was 4 x C cell...). Most of the cells are still reading 1.47-1.5 volt on the multimeter. I was planning to use it as my daily dog walking torch for up on the hills to try to burn through the 40 odd cells knocking about.

However, it seems very dim for a 200 lumen light, even if those are only emitter lumen and not ANSI (unsure how manufacturer rates output). I initially benchmarked it against my Lumintop ED10 key chain light (CR123) which is 180 ANSI lumen. The Key ring is brighter in spill and beam.

I have also benchmarked against my Zebralight SC60 running on a single nimh AA cell which is also rated 200 lumen - this is also noticeably brighter running on only 1.5V.

I love the build of the light, it looks and feels nice, but I am wondering if I have a faulty emitter? I'd put the output somewhere near 100-120 lumen by eye taking into account how floody it is. Anyone else have a Mentor and care to comment on its performance?

One strange discovery is that the light does seem to run noticeably brighter on 2 x AA Ansmann Nimh in AA-C converters? I find this a bit odd (I am by no means a battery expert ) as they are 1.2v compared to the alkaline 1.5v? Something to do with current perhaps?

Was wondering whether to send the light back to be checked or if this is par for the course?

Any views welcome. Cheers, Scrumpy.

Alkaline Cs that read under 1.5v open-circuit are near dead. NiMH cells deliver high current better than same-size alkalines, and also do better than weak larger alkalines (alkaleaks). Alkaleaks (their proper name) drop voltage considerably under load, and I think that this is what they're doing - handicapping the light's output, too. A mag 2 or 3C LED may have been a better choice in candle mode for power outages and such, or just bonus kitchen countertop light.

That does seem to make sense. I'm at a loss with what to do with all the C cells - they only had one night of use for a few hours. I do own a 3xC Mag, my wife uses it, but it seems to run forever on 3 alkaline cells and i really dont care much for its beam for dog walking. I like a good amount of doughnut free spill at my feet with a bit of throw for identifying the dog in bushes etc. The mag on a tight focus is OK, but I much prefer the likes of my Zebralight which floods the path in front and to the sides really nicely so i don't go diving over any rocks.

What is the voltage range of a 1.5v alk cell? before it is useless? I just tested the ones in the 3C mag (its got a terralux 200 lumen drop in) and they are 1.38v and the light is still bright as ever. Beginning to think its a magic flashlight that runs on thin air.

I would suggest buying some brand new C cells and trying them. If your flashlight works.... game over! If your flashlight does not work brightly on new cells... return it

Ran a few more experiments. Again ran the Mentor on 2 x new Ansmann Nimh in AA-C converters back to back with new Duracell alk. I have a large back garden and the spill is about 50% brighter on Nimh. There are 3 poplar trees in a field several houses down from our house. On fresh alkaline cells the Mentor was barely able to make out the top of the middle tree – very faint, not able to make out any detail, murky blue tint. On the Nimh it lights up all three trees, individual branches visible and with an apparently whiter tint. Almost comparable throw to my 3 x C cell Maglite with 200 lumen drop-in, ultra clear lens and polished reflector on tight focus.

I'm now more happy with the light, but I am baffled why it runs so much better on Nimh. Perhaps something to do with current or voltage under load? Never had such a difference between cells on a light before, if anything fresh alkaline are normally brighter than Nimh for the first few minutes. Weird.

Still don't know what to do with all those C cells!

scrumpy said:

Still don't know what to do with all those C cells!

Click to expand...

High power LED lights slurp current like it's tasty juice, and alkaleaks drop voltage when you put high demand on them. With all those C cells, hrm. How many exactly: dozens, or hundreds?

Rayovac sells a decent made-for-alkaleaks 3C flashlight. It may make a decent dogwalking light but you'd have to try it out. Next time you're near Home Depot look for them - "Indestructible" brand in red/black boxes.

Have 40ish used for one evening in the led lights used to dress stage etc at wedding and another 10 or so unused in a bag somewhere. I will keep the mentor as I like the lights balance of spill and throw as well as its feel, but its going to have to run nimh. I live in the UK so no home depot, most of the stores locally sell either maglite or cheap rubbish million candlepower stuff. The 3c mag I have seems to run for hours on a set of alks at constant output - im never going to get through all those cells! I might have to get my old lightsabre out of the loft - think that was 3xC .

C seems to be the forgotten cell of the flashlight world!

Not adverse to importing a light if anyone knows of a better candidate out there.