NiMH vs. Protected Li-ion for ROP & Mag85

RichS

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The question regarding which battery configuration to use (specifically for the ROP and Mag85 mods) has been a source of frustration for me when researching these two mods over the last week. The NiMH option is pretty significant expense, and it looks like I already wasted some money on Kai adapters that I'm now told won't work in either of these mods.

After reading several reports of people successfully using AW's protected 18650 cells - a common battery for most of us, this easily seemed like the best way to go with either of these mods. Still, it seems like the bulk of people are still going the NiMH route, so I wonder if there is something I'm missing.

Here is my understanding of the pros and cons of each. This assumes that no extra mods are being done to lower resistance - just the basics - battery, bulb, lens, reflector, bi-pin holder (for mag85).

Please let me know if I am missing something critical with either option:

AW Protected 18650's:
Pros
- Less expensive - most already have the charger / don't have to buy adapter+cells (slide right in C light, or use cheap PVC with D light) - $12 ea, ($24 total for ROP / $36 for Mag85)
- Slightly more output than NiMH
- Don't have to let cells "rest" or run them down before using light
- Less cells / hassle (2 or 3 cells at most as opposed to 6 or 9 cells)
- Hold charge longer (but not much longer than Eneloop)

Cons
- Not as safe as NiMH, but relatively safe since cells are protected from over-discharge
- Have to cut spring down, remove anodizing from inside of tailcap
- What else??

NiMH's:
Pros
- Safer chemistry
- Fits better (with expensive adapter), no cutting down spring
- What else??

Cons
- More expensive - most will have to buy batteries+special adapter+special charger (FM 9AA adapters still sold out)
- Have to let "rest" before using or rundown
- Deplete faster during non-use
- Slightly less output than li-ions

It seems to me that Li-ion is the better way to go hands-down with either of these mods. Is there anything I'm missing that would move it more in favor of NiMH?
 
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I've been using 2 Ultrafire 18650s (2500mAh) in my 2C ROP High, and they work great. I wish I had gone with the AW ones. One day I will upgrade. But I'm obviously a fan of the Li-Ion route.
 
I prefer Li-ion because of the lower cell count alone. It just simplifies things for me with regards to the two types of lights you mentioned.
 
Can three of the new button top protected AW 18650 fire up the 1185 bulb on a single click? If so how are people running this light? I would imagine in a 3C model, but does anything else need to be done?
Are potted 1185 bulbs available anywhere?
 
- What else??
AW - LiIon 26500 (Protected, 3300mAh, 3.7v)

Pro
- ~50% Longer runtime than NiMH
- Lighter weight
- Fit inside smaller C-Cell Lights.

Con
- Expensive ($24/ea here)
- Charging from a 18650 charger will requre jumpers, and take a long time, due to higher capacity/size.

A123 - LiFeP04 26650 (Safe, 2300mAh, 3.3V)

Pro
- Meant for high current
- Flatter discharge curve than NiMH/LiIon
- Safe/Robust Chemistry
- Good price -- $13 here

Con
- Not compatible with most LiIon chargers (possible to charge with bench power supply)
- Longer than normal "C" cell

Emoli - 26700 (Safe, 2700mAh, 3.7v)

Pro
- Works with LiIon Charger
- Safe Chemistry (no "venting with flame")
- Meant for high current - Less voltage sag than 18650 or AW 26500.
- Good price -- $15 here

Con
- Lower capacity, additional length than ordinary "C" LiIon
- Unprotected - won't vent w/ flame, over-discharge can still ruin the cells. Shut off at first sign of brightness drop.
- May require adding NTC Resistor to prevent instaflash.
 
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AW - LiIon 26500 (Protected, 3300mAh, 3.7v)

Con

- Expensive ($24/ea here)
- Charging from a 18650 charger will requre jumpers, and take a long time, due to higher capacity/size.

+ Not currently available

I knew that AW's groupbuy thread had sold out, but I thought lighthound had some -- looks like I didn't notice the "sold out" notice there, too.

Either way, here's another LiIon option, which I just got to play around with today:


Kaidomain Pack (Protected, 5000mAh, 8.4v)

Pros
- high capacity, longest runtime option of the compact ROPs (read: not counting 6D NiMH...)
- Good price/Amp-hour $40 ere
- convenient pre-assembled pack

Cons
- No 3-cell, or c-cell options avaiable (supposed to be coming)
- Requires 8.4v charger, cells can't be charged separately
- Available Kaidomain charger usable, but poor quality
- Requires NTC resistor to prevent from tripping short-circuit protection on ROP-Hi
- Even with the protection circuitry, inherently safe chemistry like Emoli would provide better peace of mind for such a high-capacity pack



If I were you right now, I'd build a 4C 1185 with 3 Emoli Cells.
 
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AW - LiIon 26500 (Protected, 3300mAh, 3.7v)

Pro
- ~50% Longer runtime than NiMH
- Lighter weight
- Fit inside smaller C-Cell Lights.

Con
- Expensive ($24/ea here)
- Charging from a 18650 charger will requre jumpers, and take a long time, due to higher capacity/size.

A123 - LiFeP04 26650 (Safe, 2300mAh, 3.3V)

Pro
- Meant for high current
- Flatter discharge curve than NiMH/LiIon
- Safe/Robust Chemistry
- Good price -- $13 here

Con
- Not compatible with most LiIon chargers (possible to charge with bench power supply)
- Longer than normal "C" cell

Emoli - 26700 (Safe, 2700mAh, 3.7v)

Pro
- Works with LiIon Charger
- Safe Chemistry (no "venting with flame")
- Meant for high current - Less voltage sag than 18650 or AW 26500.
- Good price -- $15 here

Con
- Lower capacity, additional length than ordinary "C" LiIon
- Unprotected - won't vent w/ flame, over-discharge can still ruin the cells. Shut off at first sign of brightness drop.
- May require adding NTC Resistor to prevent instaflash.
This is good information 2xTrinity, thanks! Is anyone running a ROP or Mag85 config on the Emoli - 26700 that can chime in on this option? Are these roughly the size of the 18650 cells?
 
The "26700" is going to be their size. Li-Ions, and some others, use that number ID setup. First 2 numbers are the diameter in milimeters. Next two numbers are the length in milimeters. If last number is a 0, it means it is cylindrical.

So these are going to be right at the same diameter as a C battery. Length is going to be longer, not sure how much though. Thats why it was suggested to use a 4C light with 3 of these cells.
 
The "26700" is going to be their size. Li-Ions, and some others, use that number ID setup. First 2 numbers are the diameter in milimeters. Next two numbers are the length in milimeters. If last number is a 0, it means it is cylindrical.

So these are going to be right at the same diameter as a C battery. Length is going to be longer, not sure how much though. Thats why it was suggested to use a 4C light with 3 of these cells.
Thanks for the info!
 
I haven't gotten any of the new button top 18650s, but AW's previous generation 18650s powered up the 1185 on one click. They will fit nicely in a 4C without modding the spring. For potted 1185 bulbs, post an appeal in B/S/T.

Thanks a lot of the response Mudman. I didn't know they fit perfectly in a 4C. If I can find some potted bulbs I think I might try to put one together.

Right now I have a 2C ROP Low and I need more power! A Mag85 would definitely do the trick!
 
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