I was told to NOT use Eneloops..

[Gauss163]

The driver is far more likely to heat up the battery tube than the batteries are. One of the features of NiMh and NiCd sells is remarkably low internal resistance [...]

But IR increases dramatically as the cell ages. Let's look at some graphs made by AACycler. The first compares deep (red) vs normal (blue) cycles for an AAA Eneloop.

Below shows a Varta 2100 at varying rates.

 

[lightseeker2009]

Read the spec sheet for the FD45 light. The only two batteries listed are AA alkaline and AA NiMH.

When you read further about the specs, the output, both lumens and run time are based on a 2500 NiMH battery.

The cell you've linked to should only be charged by the USB internal charger.

Further reading of the 1600U battery specifications,Fenix doesn't recommend this cell in the FD45 light.

The batteries are listed on the box my flashlight was shipped in. So they must be compatible.
Edit: " *The AA batteries can be replaced by the Fenix ARB L14 1600U Li-ion batteries"
This is quoted word for word on the retail box.

 

[magellan]

The driver is far more likely to heat up the battery tube than the batteries are. One of the features of NiMh and NiCd sells is remarkably low internal resistance. That is what allows them to deliver so much current from such a small package. I've 'thumbnailed' the Internal resistance of a relatively new Eneloop AA cell at about .03 ohms. So at 5 amps, the battery itself is dissipating a whopping .75 watts. The driver however is probably dissipating close to 10 watts at 5 amps from a pair of AA's. You don't need to a genius to understand where the heating is coming from. The same designs that conduct large amounts of current from the batteries to the driver can also conduct large amounts of heat back to the batteries. Good conductors of Electricity are also very good thermal conductors as well.

Dang, that's a ridiculously low internal resistance. Had no idea. I'm copying this post to my "battery notes." Thanks!

This might be a dumb question, but suppose the light had a direct drive mode, does that work by by-passing the driver circuit completely? Does the driver switch itself or is there an external circuit to the driver that does this?

 

[snakebite]

odd to see this thread.
in my experience eneloops are the least likely to fail and have the lowest ir.
sounds like someone at fenix is talking from their rear orifice!

 

[WalkIntoTheLight]

This might be a dumb question, but suppose the light had a direct drive mode, does that work by by-passing the driver circuit completely? Does the driver switch itself or is there an external circuit to the driver that does this?

Lots of budget high-output 18650 lights use a direct drive circuit, called a FET driver. The FET driver is basically a switch that is controlled by a processor. When the switch is closed, the current essentially flows directly through the circuit. The processor can control output by using PWM and switching the FET on and off rapidly. If PWM isn't used (i.e., the light is turned up to max), the LED is in direct-drive.

This works nicely with 18650's and LEDs like XP-L and XM-L. The LED forward voltage is approximately what the battery voltage is, after some voltage sag due to the high drain (a few amps).

I don't think direct drives are used much with AA lights. Either the voltage is too low or too high. But it can work with a 3xAA light, or more commonly, really cheap 3xAAA lights. They probably have a resistor in series, though, just to make sure. So it's not really direct drive. I suppose some really cheap 3xAAA lights might use it direct, and rely on the high IR of alkaline cells.

 

[PartyPete]

I'm guessing the rep is either mistaken or just instructed to push Tenergy batteries?

I doubt Eneloops will cause harm. I've used them for years in 4x AA Fenix E41, as well as other Nimh Fenix (and other brand) lights with absolutely no problems. Both Pro and white version.

 

[MrAl]

It is strange to me that they have not recommended their own 1600mah lithium 14500 1.5v batteries.

Hello there,

Sorry, i dont understand what you are saying. That is because the Li-ion 14500 cells are more like 3.7v nominal and get charged to 4.2v when recharged. I have 14500 Li-ion cells and they are all more than twice 1.5v being around 3.0 to 4.2v during use.

Perhaps you know of one that is really only 1.5v? If so, a link would help here.

Or maybe you mean just use ONE of those cells with a fake cell acting as a short?

Either way we have to limit the top end voltage for the flashlight to around 1.5 times the number of cells it takes.

 

[iamlucky13]

Hello there,

Sorry, i dont understand what you are saying. That is because the Li-ion 14500 cells are more like 3.7v nominal and get charged to 4.2v when recharged. I have 14500 Li-ion cells and they are all more than twice 1.5v being around 3.0 to 4.2v during use.

Perhaps you know of one that is really only 1.5v? If so, a link would help here.

Fenix sells a lithium ion battery with a built-in circuit to drop the voltage to 1.5V - the model is ARB-L14-1600U. The goal, I presume, is an AA format battery with built-in USB charging, which I suppose would have been more difficult to implement with an NiMH battery.

 

[WalkIntoTheLight]

Fenix sells a lithium ion battery with a built-in circuit to drop the voltage to 1.5V - the model is ARB-L14-1600U. The goal, I presume, is an AA format battery with built-in USB charging, which I suppose would have been more difficult to implement with an NiMH battery.

It might also be useful for devices that require a full 1.5v to operate properly, which NiMH can't provide. Maybe also to provide a constant voltage, for lights that would otherwise drop output as voltage drops.

IMO, I wouldn't buy something that required such strict battery requirements.

 

[stephenk]

Lots of budget high-output 18650 lights use a direct drive circuit, called a FET driver. The FET driver is basically a switch that is controlled by a processor. When the switch is closed, the current essentially flows directly through the circuit. The processor can control output by using PWM and switching the FET on and off rapidly. If PWM isn't used (i.e., the light is turned up to max), the LED is in direct-drive.

This works nicely with 18650's and LEDs like XP-L and XM-L. The LED forward voltage is approximately what the battery voltage is, after some voltage sag due to the high drain (a few amps).

I don't think direct drives are used much with AA lights. Either the voltage is too low or too high. But it can work with a 3xAA light, or more commonly, really cheap 3xAAA lights. They probably have a resistor in series, though, just to make sure. So it's not really direct drive. I suppose some really cheap 3xAAA lights might use it direct, and rely on the high IR of alkaline cells.

Some Ledlenser lights such as the P7.2 are direct drive, with NiMH batteries not recommended.

 

[MrAl]

Fenix sells a lithium ion battery with a built-in circuit to drop the voltage to 1.5V - the model is ARB-L14-1600U. The goal, I presume, is an AA format battery with built-in USB charging, which I suppose would have been more difficult to implement with an NiMH battery.

Hi,

Ok thanks for clearing that up. So they are not the normal 14500 cells they are a very specialized cell.
That is good of Fenix to come out with such a product, but i would not have called them a "14500" cell i would just call them by their own part number. "14500" is misleading and i see by reviews that some people already made that mistake and bought them for a normal 14500 application which is 3.7v not 1.5v.

 

[lightseeker2009]

Hi,

Ok thanks for clearing that up. So they are not the normal 14500 cells they are a very specialized cell.
That is good of Fenix to come out with such a product, but i would not have called them a "14500" cell i would just call them by their own part number. "14500" is misleading and i see by reviews that some people already made that mistake and bought them for a normal 14500 application which is 3.7v not 1.5v.

I agree. It's unnecessarily confusing.

 

[GoVegan]

As some of you might recall, I had teething problems with my Fenix FD45. My batteries could not supply enough oomph for the flashlight at 900 lumens.
While I posted the problem here, I also emailed Fenix.

I just got a mail back that they do not recommend the usage of Eneloops in their lights. They claim the Eneloops releases a gas, that can corrode the flashlight, since it is waterproof and the gas cannot escape.
How true is this?

They recommended that I should rather buy this: https://www.fenix-store.com/aa-tenergy-ni-mh-rechargeable-batteries-4-pk-in-case/

I was just searching to see if there was any change in Panasonic's info relating to Eneloops in waterproof flashlights and I found this thread. (BTW Panasonic's info is still as below).

I'm very disappointed in the replies I've seen on Reddit and here when people ask the same question as you did. People seem to take it personal, and then attack anyone for saying anything negative about Eneloops, basing their replies on emotions and not facts, typical fan-boy behavior.

FYI I'm very glad that Fenix are recommending that people NOT use Eneloops in their Fenix lights as this is in line with Panasonic's own documentation (and previously Sanyo's info too). Panosonic and Sanyo have always stated:

"Can eneloop be used in underwater lights?
Please do not use eneloop Ni-MH batteries in underwater lights or other airtight appliances. Ni-MH batteries feature a gas vent that allows the release of hydrogen when the battery is misused. Gas will not be released under normal usage conditions, but hyper-electric discharge or short circuit can cause internal gas pressure to rise and gas to be expelled. This gas contains hydrogen and sealed devices can't diffuse the gas, so any source of ignition may potentially cause fire."

Some people took this to mean dive lights but it was always quite obvious to me (especially after emailing them to confirm in 2012/2013), that this also includes not using them in any IPX8 rated flashlights.
I noticed that a year or 2 later the Eneloop packaging was then amended to clearly state that Eneloops should not be used in "waterproof flashlights".

Now for many people they won't care and will continue to use them anyway, but should you do so then you take that risk with any problems of gas leaks, either causing an explosion, expanding the rubber boot out or corrosive gas destroying the internals of your light.

Me personally, I used to love Eneloops and still do in my IPX4 headlamp and mice etc, but for waterproof flashlights I stick to alkalines (which can also leak gases BTW, but do not come with the same warnings), lithium AA/AAA or for my primary EDC I switched to CR123 lights (which come with their own warnings and issues especially when using 2 or more cells in a flashlight).

So there you have it, the truth from both Fenix and Panosonic too.
Think of it like riding a bike or skateboard, you get the basic safety recommendations as to wear a helmet, but it's up to you if you do or not, I know I'd always wear a helmet.

BTW I have never purchased an Olight or Zebralight despite wanting to buy both brands, basically because they lost my trust when they both recommend Eneloops despite the official manufacture warnings, I just don't have a lot of confidence in their engineers.

 

[GoVegan]

I'll add that I would certainly purchase and use the Tenergy NiMH rechargeable batteries or the GP ReCyko+ ones too, in any of my Fenix or IPX8 lights.

Although they technically do have the potential to leak (well any battery does), I believe they are not such a risk as the Eneloops and certainly don't come with any warnings that I am aware of (I previously spent some time researching this).

 

[WalkIntoTheLight]

BTW I have never purchased an Olight or Zebralight despite wanting to buy both brands, basically because they lost my trust when they both recommend Eneloops despite the official manufacture warnings, I just don't have a lot of confidence in their engineers.

Eneloops also state, right on the package, that they are not to be used in any air-tight device:

Of course, this is all complete legal paranoia. The above warning means that you should not use Eneloops in just about every decent flashlight. And since all batteries can vent, it basically means you should not use any battery in any good flashlight.

You can follow that advice if you wish. But you should probably never leave your house either, since everything else in the world is more dangerous.

 

[fyrstormer]

Anyone who claims rechargeable batteries release gases doesn't understand how rechargeable batteries work. The chemical reaction that produces electricity must be completely reversed during the charging process. If they released any portion of the internal chemicals, they wouldn't be able to recharge properly. They may have vent holes to prevent an explosion if they are badly overheated, but that's obviously a one-time event and the batteries will not work afterwards.

Keep in mind that most flashlight companies nowadays want to keep selling you single-use batteries because that's an easy way to maintain their revenue stream. Pretty much only the boutique brands recommend rechargeables instead, because they haven't maxed-out their potential market share yet and they still have room to grow by selling flashlights instead of batteries.

 

[GoVegan]

Anyone who claims rechargeable batteries release gases doesn't understand how rechargeable batteries work.

Over discharging, high rate discharging, ambient temperature (i.e. too cold), impact from dropping, reverse polarity (when using 2 or more cells) are all some of the ways hydrogen can be released during use. I suggest doing some more reading on the topic, I remember I found the technical documents from the manufactures such as Energizer and Panasonic interesting.

FWIW I myself have had issues with a Fenix TK41 (containing 8 Eneloops) tailcap being hard to remove after long term storage, most likely due to gas buildup in the light.

 

[fyrstormer]

I think you need to go back and read my entire post, not just the first sentence of it. Venting is not part of the normal operation of any rechargeable battery.

 

[bigburly912]

I think you need to go back and read my entire post, not just the first sentence of it.

Yep. Pretty sure you called that one haha

 

[WalkIntoTheLight]

FWIW I myself have had issues with a Fenix TK41 (containing 8 Eneloops) tailcap being hard to remove after long term storage, most likely due to gas buildup in the light.

Very likely not due to any Eneloop venting. Probably just the fact that threads sometimes get stuck after awhile if not properly greased. Either lube the threads, or eat some meat to give you enough strength to twist off the cap.