Self-discharge

From Wikipedia, the free encyclopedia

(Redirected from Loss of charge)
Jump to: navigation, search
Self-discharge is a phenomenon in batteries in which internal chemical reactions reduce the stored charge of the battery without any connection between the electrodes. Self-discharge decreases the shelf-life of batteries and causes them to have less charge than expected when actually put to use.
How fast self-discharge in a battery occurs is dependent on the type of battery. Typically, lithium batteries suffer the least amount of self-discharge (around 2-3% discharge per month), while nickel-based batteries are more seriously affected by the phenomenon (nickel cadmium, 15-20% per month; nickel metal hydride, 30% per month).
Self-discharge is a chemical reaction, just as closed-circuit discharge is, and tends to occur more quickly at higher temperatures. Storing batteries at lower temperatures thus reduces the rate of self-discharge and preserves the initial energy stored in the battery. Self-discharge is also thought to be reduced over time as a passivity film develops on the electrodes.
The detailed chemical causes of self-discharge depend on the particular battery and are not well understood.




There has also been a discussion on this forum about storing batteries in the refrigerator to slow self discharge. There have been some difference of opinion with each side linking articles to support their position.

IMHO the self discharge rate of lithium batteries is so low it is hardly a concern. If you don't use them in six months, just put them in the charger and top them off. NMh and NiCad on the other hand have a much higher discharge rate and should be recharged every two to three months. (if i were using for my bike, i would make sure they were fully charged before heading out)

I just ordered one of the 8 mode lights, plus batteries and charger. Gotta try something like that out for myself! I presume it'll work with the Lockblocks I already have?

The beefier CylopBlock would be preferable for a flashlight that size and weight. Lighthound carries them, if you want to get one.

Hmm. I have 25 sets of Lockblocks here, so I'll try those first before I start shipping things in from the States, but thanks for the heads up! It doesn't look that much bigger than my Cree flashlight, but perhas looks are deceiving!

I'm using this like many here...

http://www.dealextreme.com/details.dx/sku.8274

hmmm, I just use a couple of 1/2" conduit clamps:

http://images.grainger.com/B272_31/i...ucts/2KWP4.JPG

epoxied together and spray painted black:


works like a champ. Got in an accident last week on my bike. The only thing that didn't go flying everywhere (GPS, tail light, water bottle, etc. etc. etc.) was my P7 light attached with the conduit clamps.

Great thread; lots of good information. My front light is currently one of those cheap AA models that are ok as far as being seen, but not great for illumination. I just took the plunge with a P7 kit from DX, which should greatly improve my lighting. The price is definitely right.

http://img167.imageshack.us/img167/3...ure1op2mj4.png

Picture of the P7 on my bike after tonight's ride. You can see where it sits on the handlebars in the pics in my sig.

I'm taking a guess you're gonna be thrilled compared to your old light. :)

I've had really good results with "Sanyo Eneloop" NiMh AA cells, info here:

http://www.sanyo.co.jp/koho/hypertex...1/1101-2e.html

I also have some eneloops. I put them in my wireless mouse about 3 months ago, we will see if they stand up to their reputation. :)

Battery question for the P7 owners here....

Do you guys recharge your 18650 at near empty, or do you just top it up, when it still has about 50% charge?

I run my P7 on MAX all the time, as soon as it falls to a Mid level output (like when you turn it on in middle, instead of High), then i swap battery for another fully charged one.

I guess what i'm trying to find out is if that might kill the batteries sooner than when you fully discharge it, then recharge.

These 18650 are laptop batteries, and they have no memories, so technically speaking it shouldn't cause any harm.

I top it off after every ride.
if they're protected batteries, they'll cut off at 2.7V and 4.2V

yeah, i got the protected ones, i don't want them exploding on me, when over charged :p

These P7's sounds good, but does anyone have any pictures of how much light they produce? How much brighter are they compared to these ?

There is no comparison. Those lights seem to max out at 100 lux, while a P7 has 7000 or more. Also check out the newer MC-E lights; there of P7 brightness, but with better throw and a longer runtime.

to me 50 lux is more than enough. I think i would prefer a battery pack that i can fit onto the bike somewhere and the lamp on the forks or front stem.

If you are looking for info on that your best bet would be to search or start a new thread with specific questions. This thread focuses on P7 lights.

Can anyone confirm for me the difference (other than the number of modes and price) between these 3 P7's...? I have read every post in this thread and i am still unsure :bang:

1. MTE SSC P7 900-Lumen 5-Mode Super LED Flashlight (1*18650) - Price: $39.51; DX sku.12060
2. MTE "P7-D" SSC P7-C 5-Mode Memory 900-Lumen LED Flashlight (1*18650) - Price: $47.99; DX sku.16092
3. MTE SSC P7 C-Bin 900-Lumen 8-Mode LED Flashlight (1*18650) - Price: $42.96; DX sku.13060

Thanks!

You switched 13060 and 16092. Don't get 12060; it's unregulated. Between 13060 and 16092, I'd get 13060, which I have, because it has more modes (the strobes come in handy) and an assault cap (which lets you see the light when standing the light on its head, among other things). It's also a bit cheaper.

Thanks! I fixed the links in my post.

So between 13060 and 16092, 13060 has more modes, yet 16092 is more expensive. Is there a stated reason for that one being pricier - better light, longer lasting, etc...?

It's just because 16092 is new; when 13060 debuted this summer, it was also 47.99. It just dropped to 42.96 a week or two ago. 16092 came out a month or so ago, so it's still under "new" pricing.

Oh, interesting. I guess that's what happens when I come in "late" in the game. Thanks for all the help...now on to convince the wife that i need more cycling gear...

we hear ya man, we hear ya. ;)

Run time for 18650 P7s from DX?
 

I went for a ride today (during the day) and had my flashlights mounted. I'm running two MTE DX P7s (8-mode) on the bars. I figured since they are there I might as well use them to be seen better.

I haven't been riding outside so they haven't been charged in two weeks but have been used for dog duty almost daily. I had one on the steady 2hz blink for the entire 2.5hr ride. When I got home I thought I'd run them both all the way down. They've been going in the garage for over 4hrs on the high setting. I'd say one is about as bright as the normal low and the other is a little less than the normal low but they are BOTH STILL GOING! :thumb: Seeing them keep going even in super low output makes me feel better about riding longer at night. I usually ride with one on high and keep the other as a backup (unless I'm going down some big hill).

I thought they would have reached the cut off point of the battery voltage by now. I'm using the Trustfire 18650 Li-on 2500mAh protected cells from DX.

Has anyone done a run time test with the MTEs and these batteries?