Problems with the STEN battery?

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Problems with the STEN battery?

Postby RichBCAG » May 9, 2008 8:50 am

Has anyone else here had any issues with the Li-Ion battery that comes with the Sten? I've had 2 crap out on me now for reasons that aren't entirely clear to me.

Both times this has hapened, I had run one battery down and was going to change out to the spare. When I pulled it out of my cave pack and battery bag, there was no blink upon plugging it in and I got nothing. Current test at home shows no juice at the plug. :doh:

I think it may be in the connector at the end of the wire, but the one battery that I tore apart (looking for a broken connection) seemed to be broken somewhere at the circuit board (what is that in there for, anyway?).

Anyone have any ideas? Anyone have a good alternative to the 8.6V Li-Ion packs?

Any help would be greatly appreciated,
-Rich
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Re: Problems with the STEN battery?

Postby potholer » May 9, 2008 9:37 am

If there's a circuit board in a lithium battery pack, it's likely a protection circuit against overcharge and overdischarge, (both of which can lead to unpleasant consequences), and in a multicell pack with cells in series, the circuit might also be doing some charge-balancing (to prevent one cell becoming overcharged if it reaches full charge before one or more of the cells in series with it).
A circuit might also do some kind of protection against excess current draw.

Did you contact the manufacturers?
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Re: Problems with the STEN battery?

Postby boogercaver71 » May 9, 2008 2:18 pm

Ive had my Sten about 3 years and I had one battery crap out on me. I thought that it was impossible to over-charge the battery. I still have my AA battery pack that can attach to it but I dont know how one would keep it dry since it's wide open
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Re: Problems with the STEN battery?

Postby Mark620 » May 9, 2008 2:38 pm

potholer wrote:If there's a circuit board in a lithium battery pack, it's likely a protection circuit against overcharge and overdischarge, (both of which can lead to unpleasant consequences), and in a multicell pack with cells in series, the circuit might also be doing some charge-balancing (to prevent one cell becoming overcharged if it reaches full charge before one or more of the cells in series with it). A circuit might also do some kind of protection against excess current draw.


The circuit does all of the above.
Actually Li-Ion batteries need special care - DO NOT dent/crush them - they will vent flames/explode
NEVER EVER recharge a Li-Ion battery that is below 2.1 volts - they may vent flames/explode - fortunately the protection circuit does this - it does not allow it to be recharged if it is over discharged.

My original sten battery died and my charger also died - it would no longer charge a Li-ion battery

Since then I have learned a lot about Li-ion batteries and their dangers...
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Re: Problems with the STEN battery?

Postby nordicjw » May 9, 2008 5:06 pm

I had a problem with my sten battery also. I always recharge after a trip, so I'm ready to go whenever. Some time pasted before I tried to use the battery, when I did I got the same result, no flash when I plugged it in. I plugged in my 6AA pack, light worked fine. I tried to charge the battery, nothing. I contacted Sten, they said I must have exceeded the life of the battery, no way I had not used it that much or had it that long, but I was beyond the warranty period. I checked my charger the output was correct.

They said I could send it back to them, they would check it out. I decided to take it apart myself, curious. After some basic tests it appeared that the board was the problem.

Whatever is causing this problem Sten should be looking into it. Sure it made it thru the warranty period, but I did not get the life out of it that I expected. I am still pleased with the light, but have not replaced the battery pack yet. I was thinking about the larger battery pack, but I can buy alot of rechargeable AA for $80. As was previously mentioned the 6AA pack is not waterproof, which I'm not happy about. I knew that when I bought the acc. kit. At the time I expected it to normally reside in my pack as a backup.
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Re: Problems with the STEN battery?

Postby wyandottecaver » May 9, 2008 6:12 pm

sooo buy the sten light and have someone competent build you a battery?
I'm not scared of the dark, it's the things IN the dark that make me nervous. :)
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Re: Problems with the STEN battery?

Postby driggs » May 11, 2008 1:33 am

RichBCAG wrote:Anyone have a good alternative to the 8.6V Li-Ion packs?


While the StenLight can operate on a battery of up to 18V (with less electrical efficiency), the stock Li-ion battery is 7.2V.
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Re: Problems with the STEN battery?

Postby Mark620 » May 11, 2008 12:55 pm

This appears to be the battery that sten packs with their light:

http://www.batteryspace.com/index.asp?P ... rodID=2439

it comes with no connector.
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Re: Problems with the STEN battery?

Postby FiddleCaver » May 11, 2008 10:39 pm

Li Ion battery packs can be a little troublesome. They don't like to be kept at full charge for long periods of time. They don't like to be charged when they have not been discharged a reasonable amount. If you let them sit, they discharge on their own. And, they don't like to sit discharged for long periods of time. My suggestion is to name or mark your batteries so you can distinguish between them and cycle using one on a trip and the other the next trip. If there is a long period of time between trips, the best thing to do is to partially discharge them - between 3.5 and 3.7V per cell. At this voltage they can self discharge without worry and are not sitting at a full charge. BUT, by far the best performance of a li-ion battery will be with fairly regular use, to use it from a full charge all the way until the protection circuit cuts it off, and then charge it within a reasonable time and start the cycle over. You should get ~1000 cycles of this before the batteries are worn out.
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Re: Problems with the STEN battery?

Postby Mark620 » May 13, 2008 11:25 am

Silverfox at CPF disagrees with that and the sten battery consists of two of the 18650 batteries.

SilverFox wrote:04-19-2006, 09:56 PM
On March 24, 2005 I charged an unprotected 18650 Li-Ion cell up to 4.000 volts and placed it in room temperature storage.
A few hours later it was at 3.989 volts.

On March 26, 2005 it was at 3.976 volts.

On May 14, 2005 it was at 3.975 volts.

On October 1, 2005 it was at 3.974 volts.

On December 11, 2005 it was at 3.973 volts.

On February 10, 2006 it was at 3.973 volts.

On March 2, 2006 it was at 3.973 volts.

On April 19, 2006 it is at 3.973 volts.

Not much in the way of self discharge...

Tom
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Re: Problems with the STEN battery?

Postby FiddleCaver » May 13, 2008 11:56 am

I didn't say how much they self-discharged. Besides, go look at a graph on voltage vs charge on a li-ion cell. It's not linear so when you're closer to a full charge, the voltage drop for a specific amount electric charge isn't as pronounced as when you're fully discharged. If somebody really wanted to test this correctly, you would need to measure the voltage and the remaining capacity at several points during a self-discharge. And... It might take a while because the truth is that they don't discharge all that quickly. But, it could ruin a battery that sat for a few months fully discharged.
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Re: Problems with the STEN battery?

Postby Mark620 » May 13, 2008 1:55 pm

I do not disagree with that.

2.75 volts is fully discharged for a single Li-Ion battery while 4.2 Volts is fully charged.
A Li-Ion battery that has 4.0 volts is approximately 80% full.


Anyone who is not familar with 3.6V Lithium Ion (Li-Ion) rechargeable cells should definitely do some research before buying or using them. They require some caution to charge and use safely and can be dangerous if mishandled (they can vent hot gases or explode). Note that you'll need a smart Li-Ion battery charger. When charging Li-Ion cells the charging current in mA should be kept under the rated capacity of the cell in mAh (this is called 1C). Charging current greater than 1C is bad for Li-Ion cells.
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Re: Problems with the STEN battery?

Postby Jeff Bartlett » May 13, 2008 3:55 pm

I don't understand when we started expecting more than 2 years or so from a lithium ion battery. Isn't that their functional lifespan in things like cellphones and laptops, let alone with frequent use in a harsh cave environment?

Those of you faulting Sten for this are way off-base; they're just making use of available technology, and aren't personally responsible for the limitations of it. If you'd like to wear 6 AAs on your head, or prefer what electric caving was like 15-20 years ago (big D-cell and lead acid battery packs worn on the waist), you go right ahead.
"Although it pains me to say it, in this case Jeff is right. Plan accordingly." --Andy Armstrong
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Re: Problems with the STEN battery?

Postby Mark620 » May 15, 2008 12:35 pm

A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. This drawback is not widely publicized.

At a 100% charge level, a typical Li-ion laptop battery that's full most of the time at 25 degrees Celsius, will irreversibly lose approximately 20% capacity per year. This capacity loss begins from the time it was manufactured, and occurs even when the battery is unused. Different storage temperatures produce different loss results: 6% loss at 0 ?C, 20% at 25 ?C, and 35% at 40 ?C. When stored at 40% charge level, these figures are reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.

If the battery is used and fully depleted to 0 %, this is called a "deep discharge" cycle, and this decreases its capacity. Approximately 100 deep discharge cycles leave the battery with about 75% to 85% capacity. When used in laptop computers or cellular phones, this rate of deterioration means that after three to five years the battery will have capacities that are too low to be usable.

Li-ion batteries do not suffer from the memory effect, but they are not as durable as NiMH or NiCd designs and can be extremely dangerous if mistreated.

Li batteries are usually more expensive, since they use a newer chemistry and have more advanced applications.


Permanent Capacity Loss versus Storage Conditions Storage

Temperature 40% Charge 100% Charge
0 ?C (32 ?F) 2% loss after 1 year 6% loss after 1 year
25 ?C (77 ?F) 4% loss after 1 year 20% loss after 1 year
40 ?C (104 ?F) 15% loss after 1 year 35% loss after 1 year
60 ?C (140 ?F) 2 5% loss after 1 year 40% loss after 3 months

Source:
http://en.wikipedia.org/wiki/Li-Ion
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