View Full Version : battery life question (for the electrical geeks:)
As an "old school" kinda guy who is just getting into ARs, I have a question about battery life and some of the new optics.
I believe it is Aimpoint claims 8 years (or whatever) of constant-on use - with a AA battery. My question is this - If I leave a AA in the kitchen drawer for 8 years, it will be dead when I try to use it. Not that I ever plan to test the claims, but isn't it a bit of an exageration to claim the constant-on life that some manufacturers do? Won't the battery die from age as opposed to draw?
john
Lithiums are supposed to have a very long shelf life and I don't think 10 years is out of the question. WRT alkalines, not as great. You have a valid point.
Pat_Rogers
10-15-07, 11:42
jmoore- that is an excellent question. I am told that Aimpoint did accelerated testing in order to arrive at these figures, but beyond that, beats me.
However, i'll make an inquiry.
Sidewinder6
10-15-07, 12:29
Its called self discharge and you may read more by going here:
http://en.wikipedia.org/wiki/Self-discharge
Litiuum battery last as long as 10 years on a shelf but once you start using them, this curve changes. Many of the carbines and accessories have a place where you can place additional batteries for optics. Its a good idea to fill them.
Here is a rule of thumb for Ops from a technical point of view. If you use the batteries on an op, chuck them immediately when you get back. Always go out with fresh batteries and extras. In the Tech world, it is called the ABC's that cause you all the heart ache. Antennas, Batteries and Connectors. In this discussion, only 2 out of the three apply.
For storage or less severe use, make sure the device is actually off. Sometimes a device may be off, but it is still pulling current and this is a death sentence for a battery.
I will be interested in the info that surfaces on this subject from the manufacturers.
soo..... what was the consensus of this research?
I read this a while back, but just wanted to know if anything knew was learned.
I just read a posting from someone that was over in the sandbox and he stated he had to change his battery 3x's in 1yrs. time.
Pat_Rogers
10-16-07, 08:50
I just read a posting from someone that was over in the sandbox and he stated he had to change his battery 3x's in 1yrs. time.
Rob- that is partial information, and without knowing specifics, is not too viable.
For example- which Aimpoint. The M68 covers the Comp M2, M3, and M4. All have different electronics, and different battery life estimates.
However, the big fly in the ointment is batteries. Not all batteries are the same. Certainly Lithium is the better choice, and what i use.
However, this may not always be possible.
I have tested brand new batteries just off the shelf that were non functional.
It is a common problem.
I did take an AA out of an EO that was "dead" and place it in an M4 and it worked. It is a little over a month now, and still functional.
I did take an AA out of an EO that was "dead" and place it in an M4 and it worked. It is a little over a month now, and still functional.
Eotech's probably draw more to generate the reticule so when the battery falls below a certain threshold, it won't have enough juice to generate the reticule. Aimpoints draw less, so that's why a "dead" Eotech battery can work in an Aimpoint. It's also why Aimpoint can get such tremendous life out of a single battery -- it simply draws so little the battery lasts a long time.
Pat_Rogers
10-16-07, 09:24
Correct- and one of the multiple reasons why i use Aimpoints.
Anecdote on batteries... Earlier this year I was cleaning out some storage and found a camera and lithium 123 batts that had been there for 10-12 years. I pulled the batts and ran them in a 6P for quite awhile, seemingly only slightly less time than I would've gotten from a new set. I believe they were Duracells.
Buying quality batteries makes a lot of difference. I've had bulk-orders of imported economy 123's that didn't go half as long as the set above. $0.99 Rayovacs at the Walmart, and their button-cell equivalents, are junk in my experience.
One of my colleagues recently acquired an Eotech, and has replaced his (AA) batteries twice in a terribly short interval. Most recently, he put some lithium AAs in, so we'll see. I prefer lithium, especially in stuff that counts.
I'm also of the opinion that batteries should be replaced periodically in stuff that counts to hedge the bet. My device might go umpteen thousand hours, but I feel better if I know the battery in it is no older than X amount of time.
Pat_Rogers
10-16-07, 11:54
From the head tech guy;
Shelf life:
Lithium= 10 yrs
Alkaline= 8 yrs
An Aimpoint with ACET (M3, ML3, M4, T1) w/ 2 moa dot at med setting will draw less then the battery packaged on the shelf.
Poster stated that curve changes as you use them. Correct, and generally i will destroy/ damage items long before it becomes an issue.
Another factor is that new technology is fast moving, and what was great yesterday is mediocre today.
I replace Aimpoint batteries on my hard use guns 1x yearly. However, on the student guns 1 will replace at 3 years or as needed.
On my EOtechs i replace batteries constantly...
Hope that helps....
Here is a rule of thumb for Ops from a technical point of view. If you use the batteries on an op, chuck them immediately when you get back. Always go out with fresh batteries and extras.
Thats a great habit Sidewinder that I also adhere to. If I use my X200 on my pistol quite a bit over a few shifts then I replace them with new and toss the old batteries in a bag for training.
If you save them for training then you don't have to worry about wasting batteries and if they go dead, well it just makes you improvise during your training so you can adapt to good ole' Murphy!
Rob- that is partial information, and without knowing specifics, is not too viable.
For example- which Aimpoint. The M68 covers the Comp M2, M3, and M4. All have different electronics, and different battery life estimates.
However, the big fly in the ointment is batteries. Not all batteries are the same. Certainly Lithium is the better choice, and what i use.
However, this may not always be possible.
I have tested brand new batteries just off the shelf that were non functional.
It is a common problem.
I did take an AA out of an EO that was "dead" and place it in an M4 and it worked. It is a little over a month now, and still functional.
Pat, I realized that after I typed it. Still lends credence to "if you have a battery powered optic, have spares on hand".
Pat_Rogers
10-17-07, 05:11
I agree about spares (for anything) 110%.
Aimpoint failures are generally rare, and most Aimpoint problems are battery related. Having said that, older models will puke more often then newer models.
Not having spare batteries is dumb.
toddackerman
10-17-07, 18:57
I agree about spares (for anything) 110%.
Aimpoint failures are generally rare, and most Aimpoint problems are battery related. Having said that, older models will puke more often then newer models.
Not having spare batteries is dumb.
Amen to that Pat!
I just got an M3 from Grant, (stated 50,000 hours, or over 5 years run time on the middle setting), and without even thinking about it, I included a spare battery with the order.
I have been in "Hi Tech" for most of my life and have worked with some pretty significant battery backed up systems. Especially in Life Sustaining Medical Equipment. I have seen for myself everything that has been posted here 1st hand. Hence, I immediately test all new Lithium Batteries for serious applications BEFORE I shelve them to make sure they weren't rejects out of the box, and then I only keep them for 1/2 of the shelf life date code before moving them to non-serious applications like the remote for the TV, or General Purpose Flashlights.
I plan on replacing the Aimpoint battery at 2 years Max.
Tack
A pic of the prototype for one of my solutions.
Eotech with "on-board" unbreakable solar charging for the AA models.
http://photos.ar15.com/WS_Content/ImageGallery/Attachments/DownloadAttach.asp?sAccountUnq=53166&iGalleryUnq=1956&iImageUnq=55223
A pic of the prototype for one of my solutions.
Eotech with "on-board" unbreakable solar charging for the AA models.
That is really neat.
If I may ask:
What type of what chemistry and how many cells is this using? Where are the charger electronics, is it a smart charger? Solar cells embedded in epoxy? Any thought to adding a plug and putting a larger solar rack in something like a hand guard cover?
That is really neat.
If I may ask:
What type of what chemistry and how many cells is this using? Where are the charger electronics, is it a smart charger? Solar cells embedded in epoxy? Any thought to adding a plug and putting a larger solar rack in something like a hand guard cover?
This is a 2 AA cell unit.
I use NiMh chemistry to eliminate the charge "memory", for this use, because I felt it was a better fit for the application.
It is "self-regulating" by design, so no worries about overcharge. Very simple circuit design.
The solar cells are the amorphous type on a flexible substrate that is about the thickness of a couple of sheets of typing paper. They're unbreakable. No glass anywhere in this charging system. In this application I used the existing protective arch on the Eotech as the framework.
It's not totally indestructible, but drops and such are no problem. Some reasonable care should be taken to not scrape the solar panel with any undue force, and keep volatile chemicals off of it, which could cloud the polymer protective layer.
I also make a battery-charging buttstock based on the Crane/LMT type stock with the battery tubes, so they can charge while in the battery tubes of the stock. One model that I sent to Crane NSWC for evaluation also had a plug on it for detonating Claymores, and thus reducing the need for the "clacker".
I could also make specialty units that could go on the handguard covers as well. I've considered this for a possible future project.
Charging capacity is limited by the amount of available surface area.
I've been doing stuff like this for a number of years now, on a limited custom basis for individuals who had some special needs.
I showed it to L3 at last year's SHOT Show. I don't know whether they are interested in buying this design, or not.
They seemed very excited about it, but nobody from L3 ever called me about it.
Very nice!
I'm also wondering, what is the approximate rating of those solar cells?
This particular panel is rated 3v @ 25ma.
Open circuit voltage is of course higher, but this is about what we'll get out of the system.
As battery voltage varies with state of charge, the current will increase or decrease according to voltage drop at any given state.
Reverse current discharge protected, too.
This particular panel is rated 3v @ 25ma.
...
Reverse current discharge protected, too.
The current direction issues were my next question.
Sending you a PM.
I believe it is Aimpoint claims 8 years (or whatever) of constant-on use - with a AA battery. My question is this - If I leave a AA in the kitchen drawer for 8 years, it will be dead when I try to use it. Not that I ever plan to test the claims, but isn't it a bit of an exageration to claim the constant-on life that some manufacturers do? Won't the battery die from age as opposed to draw?
It will die from self-discharge, draw, or other battery failure. Aimpoint is basically saying that their draw is about on par with typical cell self-discharge.
Sleep states for some micros can be 10 uA range and still do useful stuff. Assume 2500 mAh of extractable power in the cell yields 250000 hours or about 30 years if the cell didn't decay. The circuit likely consumes more than this but probably not much more, 10-30 uA range.
The expiration dates on cells are based on a calculated MTBF (Mean Time Between Failure) with a defined "failure" criteria, usually capacity drops below X% or Y% of cells have failed completely. Some or most cells will work well beyond this at reduced capacity compared to new, but others will fail early. The results are really a bell curve heavily influenced by temperature/storage conditions, batches will vary and the manufacture picked a set of data to project their date on "average cells in normal storage conditions". Basically, the older cells get the more failures out of the box you are likely to see.
Other things to consider are what voltage the device shuts off at, this will determine the available capacity of the cell at a given temperature. Lithium cells provide the least variance and the best voltage retention through discharge.
So if you throw good cells into an aimpoint, yes, they might work for 8 years. Chances are much better with lithium than alkaline cells. I probably wouldn't keep an alkaline cell in a device I care about for more than 3 months anyway. The risk of leaking is too high for my comfort - even with good cells. Though good brand names guarantee their cells and you can get usually your device replaced if damaged by bad/leaky cells.
Keep in mind with temperature extremes batteries can die very easily.
In Iraq in the summer I go thur a few battieres a week in my GPS (AA Lithiums) even when not on -- the heat just kills them dead.
I'm a simple guy... I try not to get to wrapped up in all the geeky tech stuff.
I have an older M2... I leave it on (by accident)all the time... the first battery in it lasted a year.
that was 3 1/2 yrs ago.
I keep spares.. I change it once a year regardless if it needs it or not.
The battery life on Aimpoints (newer ones) has been so established.. I don't even consider it something to think about any more.... I'm to busy trying to find cheap ammo to get out and practice with......;)
everything has a shelf life (includinmg Uranium) so unless your using a Rock for a optic.. keep spares... change yearly.... you'll be fine.
Submariner
11-26-07, 12:09
everything has a shelf life (includinmg Uranium) so unless your using a Rock for a optic.. keep spares... change yearly.... you'll be fine.
You can buy a lot of good, spare batteries for the difference in price between a nice pre-owned and hardly used M2 and a new M3. And even more on the difference between the M2 and a new M4.:D
The difference can go into training and ammo.
And if you need a 2 MOA dot (and don't dive), try a C3. Used, of Coors. And with an LT mount, bought right here on Member Sales.;)
The posted life span for the CompM4 is based on the newer AA Alkalines that have a 7 year shelf life. Lithiums of course have a 10 year shelf life. As mentioned the Advanced Circuitry in the Aimpoint sights draw the same amount or less energy than the self discharge. The 8 or 10 year life is based on the optic being set on setting 12 of 16 (7 night vision and 9 visible settings). The CompM2, ML2, M3, ML3 each have 10 settings (4 NVD and 6 visible). The stated battery life is based on setting 6 of 10. 10,000 hours (8760 hours = 1 year = 365X24) for CompM2/ML2 and 50,000 for CompM3/ML3/C3. The 5 year life for the Micro T-1 sight is based on setting 8 of 12 (4 NVD and 8 visible). Keep in mind that you will adjust the brightness up or down based on the mission environment that you are operating in, thus battery life is effected. Also, as KevinB mentioned heat and cold effect the life of batteries which is why lithium is highly recommended for serious use as the variance is reduced. The benefit of optics using AA batteries is that you can at least purchase or procure (for us Marines) less expensive alkaline batteries in a pinch.
S/F
Submariner
11-28-07, 07:29
Were you ever able to find the cut-off serial number where M2 electronics were improved (as stated in another thread)?
Paul,
No, but basically any made after 2005 will have the newer circuitry. If I find out more I'll let you know.
S/F
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