Fenix L2D + NiMH + winter = problems?
 

Has anyone else tried a Fenix L2D with rechargeable NiMHs in cold weather? I'm getting about 30 minutes of burn time in my commutes at about -5C temps. This morning, I switched to the weakest setting when I noticed the full blast started to fade quickly. I run that for about 20 mins, and then I had the next 2-3 power levels available again. But on another similar occasion, the light practically died and I had to use my backup.

At first I thought it's because the NiMHs I have are old and no-brand, but this morning I had a freshish pair of Energizer 2650mAh batteries. No difference. Now, after resting a couple of hours in the office, the light seems to work ok. Funny thing is, my rear LEDs use similar or weaker NiMHs, and they all operate flawlessly. Of course their LEDs come nowhere near in light output (or power drain) compared to the Fenix.

Maybe I'll try to insulate the light (not the lighthead) a bit. Rechargeable NiCads would take cold better, I hear, but they don't seem to be widely available anymore around here. Any other suggestions? Using disposable alkalines is not an option, I'd have to buy a new set every day.

--J

Too cold
 

Are you leaving the light on the bike? We often have below zero (F) temps and I've found I need to bring both my front and rear lights inside at night to get decent performance from them. My rides in these temps are just over an hour and they work fine with NiMH batteries. Insulation wouldn't help if the light is in the cold all night but might help if you store it in a heated environment.

i'm one more person not happy with L2D runtime, nowhere near the claimed one... But you should expect numerous pro-Fenix posts on your way

No problems here in Riga. I'm getting over 2 hours of run time with both my helmet and bar mounted lights. Same thing when it was recently -12.

FWIW I've had problems with Energizer batteries self discharging in literally hours. I've had no problems with other brands. I'd guess that you have 2 bad batches of batteries.

EDIT: I'm using Duracell 2650 and Hama 2700 batteries.

ANOTHER EDIT: I've heard that LSD batteries can handle the cold better. The GP ReCyklo I just bought mentions they perform just fine at -10.

I take all the lights inside, with one exception: one of the rear LEDs is bolted on rear rack. That one obviously stays outside. I don't have any issues with that light, go figure. Or with any other "older generation" LEDs I have, including a backup front LED. It takes 3 AAAs, provides enough light to be seen, and is generally a pathetic candle compared to Fenix. But it also gives me zero problems in cold weather. And -5C really isn't that cold.

--J

Thanks for the tip Z, I think I'll give the ReCyko a shot next. I've been eyeballing them, but have left them on shelf so far because of the smaller nominal capacity vs. slightly higher price. I didn't realise they might have an advantage in colder temps as well.

Burn times have been ok for me with alkalines, they get close to what Fenix claims. I just need to find rechargeables that can get me in the same ballpark. I'm willing to take a small loss on burn time, but the 80% reduction I'm experiencing now is a bit steep.

--J

Last week I rode at -11C last week with no problem, 3x's @ 1.5 hrs. I recharge the batteries every night Fenix is helmet mounted, using NiMH 2700mAh and comes into the lab. All red blinkies stay on the bike outside. They use rechargeable NiMH as well. So far so good for me.

What? I don't think that anyone is making any claims that are not true. I personally am reporting exactly what I have experienced which is all that I can do. I was skeptical at first about using a flashlight. But there were so many good claims that I tried it and was amazed to find the claims were not exaggerated at all!

Anybody that knows anything about batteries knows that Nimh battery performance goes down with the temperature and that an Li-ion battery is a better choice for cold temperatures.

I have experienced runtimes on several occasions of 2 hours in 30 degree Fahrenheit conditions which is equivalent to -1 degree Celcius. This was Duracell 2650 Nimh on their initial cycles. The flashlight was mounted on my helmet.

There could be a couple of reasons for his experience. First, if the batteries are older perhaps he has not maintained them properly. If he had an advanced charger he could test their capacity. Second, he may have a lowered capacity battery paired with a still normal capacity battery. The runtime will only be as long as the weaker battery. Again, he would either need to refresh the weak battery or replace it. The one time that I personally experienced a shorter runtime was found to be this exact cause after analysis of the batteries.

He also did not say how he initially charged the new batteries. New Nimh's need to be trickle charged for 24 hours for maximum initial performance. They can take several cycles to reach near maximum capacity. Although Energizers overall seem to be okay, I have seen enough negatives that I just don't buy them. Sanyo, Duracell, Rayovac, and Powerex consistently perform better than their claimed capacity and the competition in all the tests that I have reviewed.

Batteryuniversity.com is a great educational resource for understanding batteries and has enlightened me very much. It is at the top of my suggested reading list for anyone desiring more, accurate knowledge about batteries. There are also numerous sources of independent battery tests if you look for them.

This is my battery brand. Charging w/ delta V sensitivity is important to battery life and quality. You don't need a super expensive charger but the cheap ones ruin batteries.

No surprise there. What did catch me off guard was the drastic loss of light in a matter of few minutes when the Fenix runs low on juice. My other LED lights behave differently, but as mentioned already, none of them has a Cree LED either. Live and learn, I guess.

Regarding your other comments, this may indeed be a result of bad pairing (one low capacity battery in both battery sets I used). Both sets had been properly "initiated" with long trickle charge. They also have several charge cycles on them.

I try to look after my batteries, but I'm a commuter. I don't have time to do much more nursing than the long first charge, storage in 20C temp partially charged, and top-up charge before use. My charger is a "smart" charger (tests delta voltage and temperature). It doesn't have a capacity test function, but I can use a multi-meter to check battery voltage after full charge. I'll consider doing that to see how much variance my batteries currently have and maybe to get rid of the crippled ones.

Thanks everyone for your comments so far. It's good to know the thing works equally well with rechargeables.

--J

Batteries stop working, or stop working properly, in the cold. Cold stops the chemical reaction. They will work OK again when they get warm.

You could inslulate the light and even put a chemical hand warmer under the insulation. If you are almost there with just a short wat to go, you can stop and put the light under your coat for a while. That works great until the batteries get cold again. You can start out again with the batteries warmer than room temperature when you first started.

With enough insulation the light will work, but that might be a lot. Experiment.

I have had to start bringing spares for not just my fenix but for my dinotte headlight also, both AA thankfully I guess.
My dinotte doesn't seem so bad now that it is on a bike I take inside everyday and the batteries are behind the stem so protected from the wind. The fenix sitting there on top of my helmet in the wind takes a serious beating. When I was riding in last month I was having to change my batteries mid ride when I had it set on _High_! forget turbo. Today was a little more forgiving as it was a way too hot 60 degrees so it made it 2 hours on high without a problem. I had thought about using some wrap on pipe insulation for it but i'll probably just switch them when they dim out since I look weird enough.

As a fellow FENIX user myself, I find it oddly funny that peoples' experience with this excellent flashlight seem to be the OPPPOSITE of the warning on the package insert.

The insert/instructions warns that "TURBO use may cause overheating ... " (in various situations.)

In my experience in 40-50F, used in RUNNING (not even biking!), it remains cold to the touch after 1.5 hrs on turbo mode. Not even remotely warm.

Perhaps they've done too good a job with the electricity to light conversion process and now should make the light more "inefficient" so it warms up enough to keep the batteries toasty? (Just kidding, of course!)

One of the features of the fenix is that it is digitally regulated for constant brightness. So this is the difference, not the CREE LED. Is this correct, everybody, that the LED type does not matter. I think the Rebel and previous versions of the fenix have constant brightness.

When I was doing my research, I noted that almost all other flashlight performance charts showed dimming almost immediately and continued dimming at a steady rate until battery power was exhausted. Not so with the fenix as you have noted. It's brightness remains level.

I guess constant brightness can be an advantage or disadvantage. If your batteries are strong and the light is used the same way all the time, you know what to expect and it is an advantage. If you have weak batteries or are using it in conditions in which you have no experience, i.e. colder temperatures/wind chill, then the gradualy dimming might be an advantage in that you could better gauge remaining runtime. I would gladly welcome comments regarding this theory.

With regular use about the only thing that I am aware of that you should be doing, and maybe are but did not mention it, is fully discharge the batteries quarterly either by use or using a function like the discharge function that the LaCrosse BC-900 and other advanced chargers have.

Maybe instruction manual revisions have not caught up with the rapidly advancing technology? It wouldn't be the first time IMHE.:)

my point exactly, the claimed runtime obviously includes the fast drop of output and the relatively long dimmed phase... As long as the light lives up to the turbo performance it's a great focal source

I regularly ride in below freezing temps and have had no problem so far and my batteries are nothing special.

I've mentioned this in other posts but I have to say again this light continues to amaze me. I think it is without a doubt the best piece of equipment in terms of cost and performance I have and it isn't even bike specific.

Halogen lights were easy. I knew I had to recharge batteries every so often. With affordable be-seen LEDs all that changed. I couldn't keep track on how many dozens of hours I had used any particular light with one set of batteries, and whether it had been on blink or constant mode. At that point I started carrying backup batteries. I would check before ride, and change as needed. That doesn't work with Fenix.

For a commuter it's a bit of a dilemma. I would rather have a steady light throughout the burn time, but if the light dies unexpectedly in a middle of a tricky traffic situation it can be a real PITA. It all boils down to the fact that right now I pretty much cannot predict the burn time with the batteries I have. I'll have to fix that.

--J

It really sounds like the fault of your batteries rather than that of the light. I notice a dimming before my light goes out that lasts for at least ten minutes. It sounds like your batteries lose voltage all at once.

Also, my burn time has been very regular, I know that I can get two days of commuting with time to spare on one set of batteries. Try some new batteries and please tell us the results.

Yep, I'm picking up a set of ReCykos on my way home today. Will update here once I see how it goes with them.

--J

In a bike light, alkaline batteries can slowly or quickly just lose power depending on the temperature. The NiMh and the Nicads just have a shorter run time. They keep working and then just go out. The Li ion is not so bad, but it depends on the particular light, the current drain, the insulation the light has, the temperature the batteries were when you left the house, if it's in the sun, how fast you are going, all sorts of things.
There's no reason to expect different riders to get the same exact results.

NiMh have a fast self discharge, it depends on how long ago you took them off the charger. There are lots of other variables too. Different brands and even different batteries of the same model and maker will be differerent. They all have a tolerance level and they vary.

Two batteries from the same package can be different. Some things use matched or tested batteries to get a better run time. But that's a lot of trouble.

Forget getting the same as another rider unless it's a controlled test.

Hmmm, it's a shame that rechargeable lithium-ion AAs aren't available. I use my lithium pack down to -20 C and great runtimes with it. I even leave it outside at night and when I'm at work.

I'm using 2500mah energizers in my Fenix L2D. I did a bench test and got about 104 minutes in turbo, but the light got pretty warm. For commuting, I get at least 1 hour of run time (don't usually need more) using turbo in 15-32ºF weather. I carry a spare set of primaries and only had to use them once in the last three weeks (how long I've had the L2d), but that was because I tried discharging my cells after one commute with my maha charger (VERY slow discharge), and the cells were still charging in the morning. They didn't have a full charge so they went dead on the way to work.

Nimh cells will dump quickly when stored in the cold. If your bike is stored outside during the day, you will lose some of the charge in the cells during that time if it's really cold. If you are using a "quick charger" cells may peak (finish charging) before they are at full capacity. Batteries will also fade more quickly when used in the cold. Add all that together, and add that your batteries may be in bad shape, and you will get poor performance from any light.

Let us know how the new batteries worked out.

Noticed a few questions I can address:
Lithium batteries, such as Energizer E2 Lithium AA's (L91's) work better in the cold weather than alkalines and NiMH. I've taken to using these during the winter now, and they're working great in my L2D. I think they are about $15 at BJ Wholesale for 10 of them, which is pretty good.

There are indeed Lithium-ion (rechargeable) AA's available. They are designated by the number "14500" which refers to the size in mm but are unfortunately over twice the voltage of normal AA's, so they are dangerous to use in most electronics. If you have an L1D (the 1-celled version of the L2D) you can use a single 14500 but you'll lose regulation and low modes. Not optimal, but since the output of Li-ion batteries is similar to regulated it'll seem more like it's on turbo. The L2D/L1D head is designed to take up to 4.2v safely, which is the maximum output of a single Li-ion battery.

I haven't had problems with my Fenix L2D Premium using up batteries prematurely, but I seldom use mine in turbo mode. I almost always use the 2nd highest setting (or highest non-turbo setting) during my morning commute in the dark, and use the 3rd highest setting on the commute home when it is lighter out. My morning commutes are often below freezing, with afternoons generally in the 40s and 50s during winter.

Generally I can get about 4 or 5 one-way commutes between charges. My commute legs range between 45-60 minutes depending on weather, number of traffic lights that stop me, and the route I take. So, I usually get about 4 hours per charge. However, I have noticed substantial differences between different batteries. I get the longest run time from Sanyo 2700s, and much less from DuraCell 2650s and Rayovac 2500s.

One shortcoming of the Fenix light is the lack of a low-battery indicator. As others have noted, when the battery starts to get low on the Fenix, it loses its charge very rapidly. I always carry spare batteries and have had to stop several times during a commute to change batteries. To get around that, I've started changing the batteries before they get dim (usually after 4 commute legs), but sometimes I lose count and it goes dead on me during a ride.