battery life question (for the electrical geeks:)

[twl]

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.

[UVvis]

This particular panel is rated 3v @ 25ma.
...
Reverse current discharge protected, too.

The current direction issues were my next question.

Sending you a PM.

[BackBlast]

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.

[KevinB]

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.

[Harv]

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]

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.

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.

[FJB]

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]

Were you ever able to find the cut-off serial number where M2 electronics were improved (as stated in another thread)?

[FJB]

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