alkaline vs. eneloop in Fenix LD20

Good morning!

I've been using your website for sometime, and it's been quite helpful. However, I can't seem to find a clear-cut answer the following question on the site:

After reading reviews on here, I recently purchased a Fenix LD20 205 lumen flashlight (which I could not be more happy with), and I would like to know if there is a discernible difference in brightness between using alkaline and eneloops? Clearly there is a difference in runtime, but beyond that I'm not certain.

How do these batteries hold up downrange vs. traditional alkalines? My unit will be deploying within the year, so reliability will be just as important as performance.

Thank you.

LT Torian

Hi Torian, welcome to CPF.

There is certainly a wealth of info here, hard to sort it all out sometime. In a Fenix, and most other higher powered lights, the performance advantage of NiMH rechargeables compared to alkaline is due to their lower internal resistance. This means that at higher levels, the NiMH cells have a much easier time delivering the current the light requires. At the higher levels [probably medium, high & turbo on the LD20] alkalines will fade faster. On turbo, the hardest for alkalines to drive, the difference would be very pronounced. In the Reviews forum on CPF there is a test by member Selfbuilt that has runtime info for that light on both battery types. By looking at the graphs you see how much better Eneloops are for this light.

If you also need reliability, then DEFINATELY use a quality low self-discharge [abbr. LSD] battery like Eneloops by Sanyo. Duracell also has "Pre-Charged", which are re-branded Eneloops if you get the white-top ones. These are great cells - clearly the CPF favorite among NiMH.

Another good cell choice would be lithium primary batteries. They are expensive, but give great performance and have a great working temperature range.

Thrifty

There is no difference in brightness - only runtime. You want to use NiMh for run time and you want LSD batteries (like Eneloops). Non LSD NiMh batteries will go dead very fast even when you do not use the light. There is something strange in the LD20 where you loose low for a short time on fresh lithium primary cells (low and medium are the same brightness) - I've also seen this happen on fresh alkalines but never Eneloops. Low mode always works properly with Eneloops.

I copied two of the runtime graphs from the link in my first post. These are from a thread by member Selfbuilt, who shares his great review work with us on CPF.

Great information, and thank you for clarifying the question on brightness. As far as buying eneloops (I have asked this question on another thread but I will bring it up here), amazon has some four packs listed:

http://www.amazon.com/gp/product/B000IV2WAW/ref=ord_cart_shr?ie=UTF8&m=ATVPDKIKX0DER

http://www.amazon.com/gp/product/B000IDUOPA/ref=ord_cart_shr?ie=UTF8&m=A2OE3Y56Q0FF6S

There seems to be some differences with packaging labels / descriptions etc...is there any major difference between these two? One being a more recent production? I do a lot of ordering off amazon, so I would prefer to shop there if I could.

Tre, regarding your comment on using lithium batteries: is it safe to use lithiums in the LD20? I read that only alkalines or NIMH were recommended by the manufacturer.

I see no difference. It appears one was pre-charged, one not.

Do not however, buy Eneloop LITE. IIRC the last time I looked at them in a store they had lower capacity.

Roger. Just to clear, the one's I linked aren't LITES? Also, I might be missing something, but the description lists them as both being precharged.

I think you have to look at some practical considerations.

The graphs linked here show run time on turbo, but I doubt most users would use the light that way. More likely a low mode would be used most of the time with short bursts of turbo as required (?).

Eneloops have the advantage they can be recharged, so in principle you can never run out of batteries. However, you need a good charging system and time available to charge them. You also need a rotation system and a reliable way to separate and keep track of charged batteries vs empty batteries.

Eneloops have a disadvantage in that they can be damaged when used in a light like the LD20 if you repeatedly run them to depletion. (This is caused by reverse polarization of the cell in the pair that runs down soonest.) In well-ordered circumstances it is easy to time how long the light has been used and replace the batteries before they run down. But in field circumstances this may be something that is hard to manage.

Alkalines don't suffer from this problem since once they are depleted you dispose of them. Also on lower modes they will have a run time comparable to Eneloops. It depends on the usage pattern -- whether the light is on all the time, or if it is used in short bursts with resting time in between.

With alkalines there is also less problem separating fresh batteries from used ones, since the fresh batteries will still be sealed in their packaging. Also, you will know that a fresh alkaline battery has the full run time available. With a rechargeable battery it can be hard to tell the difference between a fully charged one and a half charged one.

Torian said:

Roger. Just to clear, the one's I linked aren't LITES? Also, I might be missing something, but the description lists them as both being precharged.

Click to expand...

The colour doesn't look like it. See here for pictures of the Eneloop Lites.

Mr Happy said:

The graphs linked here show run time on turbo, but I doubt most users would use the light that way. More likely a low mode would be used most of the time with short bursts of turbo as required (?).

Click to expand...

I tend to use my LD10 on 'high' with a claimed output of 105 lumen rather than Turbo at 135 claimed, in order to get longer runtimes.

The LD20 on alkalines on turbo provides 40 minutes of runtime, on high 2:25. On Eneloops runtimes are 1:27 and 3:57.

Eneloops have a disadvantage in that they can be damaged when used in a light like the LD20 if you repeatedly run them to depletion.

Click to expand...

True, and to be honest I've no idea if the current regulation in the LD10/LD20 is helping or hurting in this regard. Output drops radically at a certain point which is a clear signal to change - I've been assuming this is likely a sign that the light isn't being a battery vampire but whether they drop output soon enough or too late to shorten the lifespan of an Eneloop I can't tell. Will let you know after another hundred or so discharges.

I do assume that I won't get maximum lifespan out of my Eneloops, so I tend to cut the rated 500 recharge cycles in half when considering lifespan and I ignore what capacity might look like. I've got a pair of cells I have dedicated to the LD10 for cycling use - almost daily discharges in fall and winter - so in a few more months I should have a better idea of where this all leads to.

Ignoring capacity for a moment and only looking at 250 recharge cycles, running the LD20 on high not Turbo:

250 (recharges) * 4 hours = 1,000 runtime hours (Eneloop)
1000 / 2.5 hours = 400 cells (Alkaline)

400 alkaline cells = 400/32 ~= 13 32 packs @ 22.59 each = $293.67

vs

1 MAHA C9000 charger (high end, cheaper available) @ 57.00
1 8 pack Eneloops @ 23.14
Total $80.14

The electricity consumed in charging the cells 400 times is almost inconsequential, but certainly is far less than the difference between the two.

Counting electricity consumed IIRC, even being fairly ruthless with the Eneloop lifecycle we are approaching a $200 savings for the same light output, If you get better than 250 cycles, you come out even farther ahead. Truth be told I'd still go the rechargeable route as whether it truly makes sense or not from an ecological perspective I have a hard time using disposable cells.

All of Mr. Happy's comments on organization are spot on, only I would point out that I once found 30 some odd AA alkaline cells lying around our house - partially opened packs spilled in the junk cabinet, many of them unused - and imagine a lot of families (esp. with children) are the same! The rechargeable (and alkaline now) cells are all neatly organized in a box.

I failed to mention the worst feature of alkaline batteries. They leak and wreck your nice light. It's not so bad in the lights I used to use, junky incans that were almost disposable themselves, but for nicer lights - the kind most often discussed and recommended here - having a leak is a real downer.

@Torian: AFAIK, all Eneloop AA's with white outer wrappers are the same. $10.63 or $10.99 for four is a good price, especially if your order can qualify for free shipping. I got some good deals on them at Costco, if that is available to you.

Good information everyone. I tend to replace my alkalines every few weeks, so I don't think linkage is a major issue. I will still however probably opt for the eneloops for long-term.

On a side note, my father was so impressed with the LD20 that as soon as he handled it (and blinded me with the strobe), he bought three for himself and the rest of the family.

I just realized that I'd chosen an 8-pack of rechargeable cells to be realistic about having spares on hand but didn't adjust the costing accordingly. With 8 cells you have 4 sets of 2 for use in a LD20, so instead of 1000 hours of light (from a conservative 250 charge cycle lifespan of the cell) you have 4000.

As a result the cost per hour of light drops significantly.

Likewise I messed up with the alkaline costs, forgetting to consider the cells as sets of 2. For equivalent runtime to match the light output of 8 rechargeable Eneloop cells we need in alkaline cells:

4000 / 2.5 hours = 1600 sets cells (Alkaline * 2 = 3200 cells)
3200 alkaline cells = 3200/32 pack (Amazon link was given) = 100 * 32 packs @ 22.59 each = $2259.00

Cost to recharge a cell has been calculated as ~ 0.2 cents to recharge an eneloop and I've seen somewhere an actual power consumption measurement done that appeared to back this low figure up. Still let's take the worst case and call it a penny per charge, so we add 8 * 250 (charge cycles) * 0.01 = $20.00 (or perhaps as low as 8 * 250 * 0.002 = $4.00), bringing our rechargeable costs from $80.14 to either $100.14 or $84.14.

Putting the costs into full perspective:

Rechargeable cells:
$84.14 / 4000 hours of light = $0.02 per hour.
$100.14 / 4000 hours of light = $0.03 per hour.

Alkaline cells:
$2259.00 / 4000 hours of light = $0.56 per hour

That adds up to $1.41 to run the LD20 on "high" (not turbo) for two and a half hours if using alkaline cells, at which time the cells are spent and need to be recycled. That same runtime, with all costs in and amortized over 4000 hours of use, will cost something less than 6 cents to run the light for two and a half hours using rechargeable cells.

Clearly not everyone will use their AA powered light so heavily, so if usage is infrequent, disposable primary cells might be the right answer. Yet even the light-duty light user, if a reliable but inexpensive charger that meets the person's needs can be found, might reach a satisfactory cost-benefit tipping point that favours rechargeable cells sooner than later.

Comparing the cost of cells alone reach break-even fairly quickly:

8 pack eneloop @ 23.14 = $2.89 per cell
32 pack Duracell alkaline @ 22.59 = $0.71 per cell

Break-even point: 2.89/.71 = ~ 4 recharge cycles before your eneloops become almost "free" as compared to disposable alkaline cells.

Many of us have quite a few devices that are powered by AA and AAA cells so chances are the cost of a half decent charger can be fairly cheaply allocated across the different uses.

Of course if you are going through 3200 alkaline cells chances are somewhere along the line you will have a leaker, so factor in the cost of a new light too. That many cells also weighs quite a bit, which may result in a back muscle spasm that needs treatment, so factor that cost in too!

E&OE
(Errors and Omissions Expected)

I have an LD20 and use eneloops as I dont want my light damaged by leaking alkies.

I don't know what electricity rate they are assuming but eneloop advertises $.04 per cell charge on the multipack that comes with the eneloop/sanyo branded charger.

noisebeam said:

eneloop advertises $.04 per cell charge

Click to expand...

Thanks for that. Using 4 cents as the worst case then brings the 4000 hours of light runtime cost to $160.14 or about 4 cents an hour or for the equivalent runtime as two alkaline cells on 'high' the rechargeable cost increases to 10 cents up from 6 cents.

If you live in a nice sunny climate you could use a solar charger which would bring down costs even more!