Why 1.2V VS 1.5?

Kraid

Enlightened
Joined
Jul 4, 2007
Messages
515
Location
Waipio, HI
I've been considering switching over to rechargable AAs, but I've noticed that they are 1.2V instead of 1.5 like their alkaline breathern. Why is this, and would it give my L2D CE less juice, causing it to be dimmer? I don't understand how, say a Duracell 2650 would compare to a regular Duracell Alkaline.

Also, please correct me if I'm wrong, but a Duracell 2650 would run a L2D CE longer than an Eneloop 2000 mAh, right?
 

chimo

Flashlight Enthusiast
Joined
Sep 16, 2004
Messages
1,905
Location
Ottawa, Canada
I've been considering switching over to rechargable AAs, but I've noticed that they are 1.2V instead of 1.5 like their alkaline breathern. Why is this, and would it give my L2D CE less juice, causing it to be dimmer? I don't understand how, say a Duracell 2650 would compare to a regular Duracell Alkaline.

Also, please correct me if I'm wrong, but a Duracell 2650 would run a L2D CE longer than an Eneloop 2000 mAh, right?

The battery chemistry dictates the voltage. One of the prices to pay for NiMH.

For your last question:

Yes: immediately after charging
No: > 6 months (or perhaps less) after charging

The Eneloops (and other low self-discharge batteries) give you longer shelf-life at the cost of a slight loss of capacity.
 

2xTrinity

Flashlight Enthusiast
Joined
Dec 10, 2006
Messages
2,386
Location
California
I've been considering switching over to rechargable AAs, but I've noticed that they are 1.2V instead of 1.5 like their alkaline breathern. Why is this, and would it give my L2D CE less juice, causing it to be dimmer? I don't understand how, say a Duracell 2650 would compare to a regular Duracell Alkaline.
The way that alkaline and NiMH voltages are determined is different, which makes things somewhat confusing:

1.5V alkaline means that the battery supplies 1.5V when it is fresh. 1.2V is the average voltage of a NiMH battery as it is cycled from full to empty. A fresh NiMH cell will actually read closer to 1.4V. Also, the open circuit voltage (what you read with a meter) isn't what really matters -- in real use, batteries have internal resistance which causes their voltages to sag. Alkaline has a lot more internal resistance than NiMH, so for any sort of high-drain application (like high-power LED flashlights) NiMH cells should actually deliver higher voltage and better runtimes than alkalines. Alkalines will still win for runtime in long-term low-drain applications like clocks, smoke alarms, memory backup etc.

Also, please correct me if I'm wrong, but a Duracell 2650 would run a L2D CE longer than an Eneloop 2000 mAh, right?
Yes if you use up the Duracell 2650s almost immediately after charging them. With normal NiMH cells, if you leave them sitting on a shelf, they will gradually lose their charge (self-discharge). Eneloop cells tradeoff a little bit of capacity (only 2000mAh) in order to have lower self discharge. I strongly recommend eneloops, they're much more versatile especially if you plan to use them for everything.
 
Last edited:

Sub_Umbra

Flashlight Enthusiast
Joined
Mar 6, 2004
Messages
4,748
Location
la bonne vie en Amérique
Mrs Umbra and I use NiMH and NiCD cells for nearly all of our battery needs. We probably do over 1,000 recharges each year. We tend to use them in all devices that will not draw them down so low that it kills the cells by reversing the polarity. Ouch! Fortunately we own few devices that kill them.

Aside from what has already been said about internal resistance the rechargables also tend to have a much flatter discharge curve in general (somewhat self regulating). It should also be remembered that for many applications an alkaline cell's voltage will be below that of a NiMH/NiCD through much of it's discharge cycle -- so it's certainly not all bad news by a long shot.

One down side for some may be that using rechargables is generally not as casual as using alkalines. To get the most out of your investment it will help if you are interested enough to learn a little bit about the various cells and chargers. CPF is a great place to learn about it.

I wish more folks were into rechargables.
 

mdocod

Flashaholic
Joined
Nov 9, 2005
Messages
7,544
Location
COLORado spRINGs
You should look at the discharge graph of an alkaline cell, you may think twice about calling it a 1.5V cell, technically they are about 1.6V fresh out of the package., but at a relatively low load of just 0.5A, they are down to 1.1V with 50% time still remaining in the discharge (and they continue to loose voltage, delivering a large chunk of their capacity down in the 0.6-1.0V range). A NIMH cell will generally stay above 1.2V through 90% of their discharge into normal loads (like 0.5-2A range), so the NIMH will give you a nice consistent useful output through the discharge, where alkaline will start to dim even though it has a lot of time left on it. People end up throwing out a LOT of alkalines that still have a lot of remaining capacity because they are running devices that require more oomf than the alkaline can deliver towards the end of it's discharge.
 

Burgess

Flashaholic
Joined
Apr 10, 2006
Messages
6,545
Location
USA
Hello Kraid -


Your Fenix L2D-CE is a "fully-regulated" flashlight.

So the brightness will be identical, no matter which battery (alkaline or NiMH) you choose.


Best if you'd check out some of Chevrofreak's excellent Run-Time graphs. :thumbsup:


They will tell you everything you wanna' know about this.


Truly a case of "a picture is worth a thousand words". :)


That's what convinced ME to go the NiMH route.

:twothumbs

_
 

TorchBoy

Flashlight Enthusiast
Joined
Jan 15, 2007
Messages
4,486
Location
New Zealand
About a month ago I ran a test where I discharged a top brand alkaline (designed for heavy loads) and an Eneloop at 1 amp. The voltage of the alkaline was higher than the Eneloop for the first three minutes. The Eneloop was much more even in its output and lasted considerably longer.

Curious_character wrote a pretty good PDF about his own observations. (I wonder what that thread was...)
 

Kraid

Enlightened
Joined
Jul 4, 2007
Messages
515
Location
Waipio, HI
Wow! Very informative as always! Thank you all, you've certainly eliminated my fears! And hopefully those of anyone reading this! Now I guess I'll start researching which cells benefit my needs most.
 

Anders

Enlightened
Joined
Nov 16, 2005
Messages
637
Location
Stockholm.Sweden
Hello Kraid.

This is a disharge test with a Varta Alkaline 1,5 Volt and MAHA Imedion Nimh 1,2 Volt.
The disharge rate is 0,5 A.

After 0:37:09 Varta showed 1,20 Volt
After 3:19:57 Imedion showed 1,20 Volt

It took 0:02:00 minutes to equal voltage, 1,42 Volt




Anders
 
Last edited:

cave dave

Flashlight Enthusiast
Joined
Aug 15, 2001
Messages
3,763
Location
VA
+1 for what everybody else said, Nimh are superior to Alkaline in almost everything except clocks and remote controls.

Here is a link and chart from Chevrofreaks actual runtimes for the Fenix L2D CE. Click on link for the full review on all levels.

https://www.candlepowerforums.com/threads/155819

Fenix%20L2D%20CE%20-%20max.png
 

bp044

Enlightened
Joined
Feb 15, 2006
Messages
237
Mrs Umbra and I use NiMH and NiCD cells for nearly all of our battery needs. We probably do over 1,000 recharges each year. We tend to use them in all devices that will not draw them down so low that it kills the cells by reversing the polarity. Ouch! Fortunately we own few devices that kill them.

Aside from what has already been said about internal resistance the rechargables also tend to have a much flatter discharge curve in general (somewhat self regulating). It should also be remembered that for many applications an alkaline cell's voltage will be below that of a NiMH/NiCD through much of it's discharge cycle -- so it's certainly not all bad news by a long shot.

One down side for some may be that using rechargables is generally not as casual as using alkalines. To get the most out of your investment it will help if you are interested enough to learn a little bit about the various cells and chargers. CPF is a great place to learn about it.

I wish more folks were into rechargables.
If I use Eneloop cells in a non regulated flashlight until the out put is totaly dim or nonexistant will the cells go into reverse polarity ? If they do can they be charged or are they useless ? Would the same answer apply using the cells in a regulated flashlight until it also goes out ?
 

Sub_Umbra

Flashlight Enthusiast
Joined
Mar 6, 2004
Messages
4,748
Location
la bonne vie en Amérique
If I use Eneloop cells in a non regulated flashlight until the out put is totaly dim or nonexistant will the cells go into reverse polarity ? If they do can they be charged or are they useless ? Would the same answer apply using the cells in a regulated flashlight until it also goes out ?
Good question.

Sometimes the cells may be restored to service -- sometimes not.

Different lights will behave differently.

At the risk of generalizing, the lights I've had that killed the most NiMHs were low powered and built for wide consumer appeal. Since most consumers use disposable primary cells it gives more value to design a light to suck alkaines dry. (I had a 10 LED Nuwai that would kill a NiMH when it first started to dim.)

It depends on who the intended market is and what the designer really had in mind. A couple of examples:

The ARC-AAA is a real 'vampire' (Gransee's word) and is a tough one for a rechargable. Even though it is a one cell light and therefore cannot reverse polarity, it is designed for runtime on alkies and will draw NiMH or NiCD cells down beyond the point of no return.

On the other hand, LUX, CREE, P4 (etc) lights that need a higher amperage often won't run longer than a few minutes on alkalines and their drivers will often cut them off before damage is done to the cells because the designer knew that they'd be run on rechargables. I have ELEKTRO LUMENS lights that may be counted on to cut out before cell damage is done.

There have also been lights that signal you before their cells are run down too much but still let you continue to use them into oblivion should you so desire because the designer wanted to give the user that option in life and death situations. (HDS-EDC)

Often electronic equipment without motors (like radio recievers) will kill cells unless they are designed for HAMS, who have a tradition of using rechargables. I have an MP3 player (RIO) that allows me to select cell type in the Options to avoid damage. Way cool.

I didn't mean to sound all over the place on this but sometimes it can be tricky. One thing you can do is to try to run the light or device on alkies until it dies -- then measure how much is left in each cell. I'm not sure what the limit should be but if the voltage of the expired cells is below 1 or 1.1 volts it may not be a good idea to run it on rechargables.

I've never done that -- I just occasionally get burnt and then I don't feed those devices rechargeables again. Fortunately, usually only one is toasted when this has happend to me.

As complex as it sounds, the negatives are pretty small -- at least with us. It has really saved us a lot over the years, aside from the fact that it's very handy to just not run out of cells.
 
Last edited:

TorchBoy

Flashlight Enthusiast
Joined
Jan 15, 2007
Messages
4,486
Location
New Zealand
Most of the Eneloops I've tested have been very well matched, so I don't think it would greatly reverse charge if they started from a similar state of charge, but it's not a good way to treat rechargeables. In normal use you shouldn't take them under 0.9 volts loaded.
 

Burgess

Flashaholic
Joined
Apr 10, 2006
Messages
6,545
Location
USA
to Curious_character (Roy) --


That was an excellent essay detailing Alks. vs. NiMH. :twothumbs


Should be made a "Sticky" , eh Moderators ?


Thank you for your efforts to explain this (sometimes confusing) matter. :thumbsup:

_
 

Kraid

Enlightened
Joined
Jul 4, 2007
Messages
515
Location
Waipio, HI
The essay and all of the other info was great! I picked up the Duracell independent 4 channel charger with the 1700 mAh HR cells as a quick fix. Now I plan to order some Eneloops to use with the charger. Might buy the occasional Primaries for clocks and remotes, but otherwise, I don't think I'll ever go back. Like I did after using the crappy rechargeables available in the 80s. Now to investigate rechargeable 123s...
 
Top