Malkoff M30 on 3xAA Lithiums?

I understand that Malkoff M30, the newer versions, can take input up to 5.5V, thus I assume that 3xAA (Energizer L91 Lithiums) should work just fine? The resulting voltage should be 5.1V, given how they come charged to 1.7V in my experience.

I assume the runtime should be real similar to a Malkoff M60 on 3x123 cells?

Same question about 3xAA NiMh cells, which operate at 1.2V, resulting in 3.6V.

I want to run all permutations of the AA cell in a 3xAA body with M30. That includes L91, NiMH, Alkalines.

etc said:

I understand that Malkoff M30, the newer versions, can take input up to 5.5V, thus I assume that 3xAA (Energizer L91 Lithiums) should work just fine? The resulting voltage should be 5.1V, given how they come charged to 1.7V in my experience.

I assume the runtime should be real similar to a Malkoff M60 on 3x123 cells?

Same question about 3xAA NiMh cells, which operate at 1.2V, resulting in 3.6V.

I want to run all permutations of the AA cell in a 3xAA body with M30. That includes L91, NiMH, Alkalines.

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I think you would be fine. By the way,nimh comes off the charger at roughly 1.44v instead of 1.2. It would still be alright since the total is below 5.5v.

metlarules said:

I think you would be fine. By the way,nimh comes off the charger at roughly 1.44v instead of 1.2. It would still be alright since the total is below 5.5v.

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I know. Good point. I use Maha Powerex 2700 mAh cells as well as Eneloops.

The word from Gene just got in, as a response to my original question - "it should be fine".

Has anybody done such a thing - Malkoff M30 + 3xAA (L91s) or I am the first one (I find it kind of doubtful, here on CPF).

Any idea of the runtime? I have an estimate but wanted to compare notes.

Sounds interestng. What kind of host do you have?

Here is the 2AA and 3AA host by FiveMega.

http://candlepowerforums.com/vb/showthread.php?t=221687

Just to satisfy my curiosity, why would you want to do this? An M30 in a 1x18650 host does the same thing and, for most folks, would feel better in the hand. If the answer is, "Because it's fun" or "Because I want to" I'm totally with you. I can see that these new AA bodies that "nite" has posted are way cool. My question is whether there is some technical advantage.

Thanks for your response. I'm just a noob trying to get up to speed and I appreciate the incredible amount of information that is available here.

There are lots of advantages...

1) Cell compatibility. I have a number of devices that run on AAs. It's far easier for logistical reasons to only have 1 kind of cell that everything runs on. GPS, radio, lites.

2) 3xAA will have far greater runtime than 1x18650.

Let's do some quick math:

3xAA = 4.5V @ 2700 mAh = 12.1 Wh

1x18650 = 3.7V @ 2200 mAh = 8.1 Wh

So you can see that 3xAA has a good 50% increase in runtime over 1x18650.

According to my calculations, 3xAA are *almost* as good as 3x123 cells. The difference should be small.
Admittedly, I like the 3x123 form factor more than 3xAA or anything else for that matter, but if I like 3xAA with Malkoff M30 and it does everything 3x123 with Malkoff M60 does, I will consider removing 123s from the supply.

etc said:

There are lots of advantages...

1) Cell compatibility. I have a number of devices that run on AAs. It's far easier for logistical reasons to only have 1 kind of cell that everything runs on. GPS, radio, lites.

2) 3xAA will have far greater runtime than 1x18650.

Let's do some quick math:

3xAA = 4.5V @ 2700 mAh = 12.1 Wh

1x18650 = 3.7V @ 2200 mAh = 8.1 Wh

So you can see that 3xAA has a good 50% increase in runtime over 1x18650.

According to my calculations, 3xAA are *almost* as good as 3x123 cells. The difference should be small.
Admittedly, I like the 3x123 form factor more than 3xAA or anything else for that matter, but if I like 3xAA with Malkoff M30 and it does everything 3x123 with Malkoff M60 does, I will consider removing 123s from the supply.

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For a "fun" light, I can't say that it matters what someone uses. For a light a person might need for serious use, well AA lights do give great "interoperability"

In actuality, the above numbers are even higher for L91 Lithiums since they typically start out at 1.7V... Not 1.5V.

The numbers are higher for an 18650, too, since at 3.7V it's about dead. The M30 also draws a lot of current. Don't count on 3AA being at any kind of advantage over a good 18650. You might get good results with lithiums, but they're expensive. I don't know that you'll even get full brightness with 3AA alkalines or NiMh.

etc said:

Let's do some quick math:

3xAA = 4.5V @ 2700 mAh = 12.1 Wh

1x18650 = 3.7V @ 2200 mAh = 8.1 Wh

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Assuming you're still refering to the Powerex 2700's, that would be

3xAA = 3.6V @ 2700 mAh = 9.72 Wh

Still a 20% improvement over the 18650, but only when the NiMHs are freshly charged, and those mAh specs (if they're even accurate to begin with) will vary with different discharge rates.

OK, Let's revise this:

Code:

Lithium L91 2900 mAh:       3xAA=  4.5V @ 2900 mAh = 13.0 Wh
Duracell Procell Alkaline:    3xAA = 4.5V @ 2600 mAh = 11.7 Wh
Maha Powerex 2700 mAh:   3xAA = 3.6V @ 2700 mAh =  9.72 Wh
Sanyo Eneloop 2000 mAh:   3xAA = 3.6V @ 2000 mAh = 7.2 Wh
AW protected 18650:                       4.2V @ 2200 mAh = 9.2 Wh

18650 is not bad at all, pretty close to 3xAA NiMh Maha cells and exceeds 3xAA Eneloops.

18650 charges up to 4.2V when protection circuit kicks in and is about 50% dead at 3.7V? Anyway, not sure what voltage number to consider. If we look at 3.7V, we get:

3.7V @ 2200 mAh = 8.1 Wh

Something doesn't look right however, I think L91 should have higher runtime or else the Alkaline should have lower runtime. Shouldn't the difference be greater than 13 Wh vs. 11.7 Wh.

So I suppose in some ways 1x18650 makes more sense than 3xAA but it's a single purpose cell, whereas AA is useful everywhere and if you must, you can use almost any AA cell.

To compare with a 3x123 configuration and obviously a different module:

9V * 1500 mAh = 13.5 Wh. If I take the low value of 1450 mAh, I get 13.0 Wh. Which is almost identical to the 3xAA L91 configuration.



One more thing, L91 does not cost anymore than 123 cells, you can find them both easily at $1/each. If you can get 123s, you can get L91s.

Etc, very interesting comparisons. What do you think the actual run time would be using a M30W with 3 Powerex 2700s? Do you know how that would compare to the run time using a M60W and 2 x AW IMR 18650s (4.18v and 1600 mAh each), considering that they would have to be recharged at 3.5 v?

That would be real close to the 2x18500 AW cells I am using now with M60, and that's the configuration the 3xAA should be compared with (In my case, anyway).

Let's see, with 2x18500: 8.4V @ 1500 mAh = 12.6 Wh

In your case, that's 13.4 Wh.

Keep in mind, we should expect higher capacity 18650 cells sometime this year, if not, next year. Meaning above 2200 mAh that you can currently get and close to 3,000 mAh. These cells already exist (e.g. Panasonic) but are not protected thus shouldn't be used with Malkoff M60/M30 for example.

But imagine, 3.7V @ 2900 mAh = 12.2 Wh.

The truth is, considering 1x18650 cell, I would rather prefer the current configuration I have which is 2x18500 with Malkoff M60. It has greater runtime than 1x18650, plus I can use primary 123s. I now have 8.4V @ 1500 mAh or 12.6 Wh. If I am going to use M30, it should be with all variations of AA.

I would expect the 18500 to similarly rise in capacity in a few years, just like the 18650 cell.

So 2 x IMR 18650s with the M60 would be about the same run time as 3 x L91s with the M30? Am I understanding your reply correctly?

Right, that's what I got.

BTT