Fenix L1T V2.0 runtimes - losing high mode

I haven't seen this discussed here. If it has, please point me to the thread. This is my first Fenix light.

Looks like when the battery starts getting low I lose high mode, but it still works in low. I am kind of thinking that once high mode is lost the battery needs to be replaced for the light to be working as as advertised so the low runtime should end at that point.

I suppose it is possible that by the time high is lost, the output on low has fallen as well, but I have no way to judge that. The amount of light with a low battery looks the same as low mode with a fresh battery to my eye.

Anyone know if the runtimes on low go past the point where high is lost? Is losing high mode with a weak battery normal behavior for these lights?

BTW, I'm using alkalines.

Mark

Alkalines will not give you the high mode for very long unfortunately. I cannot put a figure on that, but it will be roughly half the time expected with a good NiMH or disposable lithium (1.7v).

III/V said:

I haven't seen this discussed here. If it has, please point me to the thread. This is my first Fenix light.

Looks like when the battery starts getting low I lose high mode, but it still works in low. I am kind of thinking that once high mode is lost the battery needs to be replaced for the light to be working as as advertised so the low runtime should end at that point.

I suppose it is possible that by the time high is lost, the output on low has fallen as well, but I have no way to judge that. The amount of light with a low battery looks the same as low mode with a fresh battery to my eye.

Anyone know if the runtimes on low go past the point where high is lost? Is losing high mode with a weak battery normal behavior for these lights?

BTW, I'm using alkalines.

Mark

Click to expand...

Yes, it's normal behavior. Alkalines will exhibit high voltage sag under heavy load, because they cannot provide enough current.

The easiest way to remedy the problem is to use NiMH rechargeables or AA primary lithiums. I would recommend buying a Sanyo AA Eneloop kit, that contains 4 AA batteries, and a charger... for about $20.

Also, the runtime on Alkalines for Fenix lights is SUBSTANTIALLY lower than the advertised runtimes, because the latter are based on NiMH rechargeables. The runtimes on lithiums will be ~15-25% better than advertised.

Runtimes here and here.

Here is chevrofreak's runtimes for the L2T. While the actual numbers do not apply to you (2AA vs 1AA) it does show how alkalines do not work well on high.
High
alkaline 32 minutes
NiMH 106 minutes
alkaline/NiMH = 32/106 = 30%
Low
alkaline 23 hours
NiMH 27 hours
alkaline/NiMH = 23/27 = 85%
If you use high consider getting NiMH batteries & charger.
If you will not be using the L1T a lot and chargeing the batteries regularly consider low self discharge NiMH - Eneloops or any of the batteries mentioned in this thread Batteries with low self discharge "LSD"

I think I can use the L2T as an example for the L1T as they use the same head. My L1T head says "L1T/L2T v2.0". Of course actual runtimes on an L1T will be 1/2 that on chevrofreak's charts.

Thank you all for the replies. My understanding is the runtime charts are generated with the flashlight in a single mode until the output drops 50%. My question was really, and your answers imply, that after high mode stops working, the battery is still cabable of sustaining low mode light output for quite some time.

I just think that with no high mode I will change the battery anyway. So in real life I will probably never fully benefit from the long low mode runtime unless I was in a situation where I didn't have access to batteries. That is, except that using low mode preserves the ability to use high mode for a longer time.

I went for the AA light because we always have a supply of cheap alkalines around for various portable electronic devices. The shorter runtime on an alkaline is not too bothersome for me. I had this flashlight with me 24/7 for almost 8 weeks on the first battery before I lost high mode. This was using a battery that cost less than 20 cents. I suspect a typical NiMH AA (non-LSD) probably wouldn't last me that long, would it?

Mark

Edit: Oops, I mis-counted. The first battery lasted 6 weeks before I lost high mode

You might want to do a search on "moon mode", as that is how most people here refer to this state (i.e. nearly drained battery functioning for prolonged time at a single low level- typically lower than actual regulated low mode).

Fenix lights are very good at drawing out a nice long "moon mode" - other makers, sometimes less so. Most enthusiasts dislike lights with a sudden drop-off "cliff" to zero output, so a long-lasting moon mode is often prized.

Certainly, by the time your alkalines have drained to the point where there's no difference between modes, I'd say it's time to replace them. My ZTS battery meter would be showing 0% output at that point (even 20% on alkaline will still allow you to see some difference). And it's not good to leave nearly dead batteries in a light - you'd hate to have them leak and corrode a good light.

selfbuilt said:

Fenix lights are very good at drawing out a nice long "moon mode" - other makers, sometimes less so. Most enthusiasts dislike lights with a sudden drop-off "cliff" to zero output, so a long-lasting moon mode is often prized.

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Thanks for the tip. I didn't know what moon mode was. I was thinking that when high mode stops working, it is a good low battery indicator, and I still have light for a while.

Mark

NiMH (non LSD) needs recharging in a month, useless in 2.

I find for indoor use low mode is quite sufficient.

An alkaline battery probably still have 1/2 it's capacity when it cannot support high mode so will still give power in low mode for a few hours.
A NiMH will die quite abruptly. My experience is 10 to 15 seconds after I notice the light dimming though others have posted up to 10 minutes.

I ran a couple of alkalines through my L1Tv2 before switching to low self discharge NiMH batteries. The NiMHs work MUCH better. Buy a Maha charger and some eneloops and don't look back.

NA8 said:

I ran a couple of alkalines through my L1Tv2 before switching to low self discharge NiMH batteries. The NiMHs work MUCH better. Buy a Maha charger and some eneloops and don't look back.

Click to expand...

That's what I did and no regrets and gulity lumens

III/V said:

I had this flashlight with me 24/7 for almost 8 weeks on the first battery before I lost high mode. This was using a battery that cost less than 20 cents. I suspect a typical NiMH AA (non-LSD) probably wouldn't last me that long, would it?

Click to expand...

Well, in the short run, alkalines may be fine... but frankly I prefer to use LSD NiMH everywhere... if only for environmental concerns.

Since they'll be worth it in the long run anyway... it makes the decision easy.