why not rechargeables?

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Postby tncaver » Dec 18, 2007 8:55 am

Barbara, you need to have a yard sale. :-)

One reason I haven't been using rechargeable batteries is
because they died after getting wet. I tried them in several
caves and discovered they were fine in dry caves but they
died every time I went in caves where the water was deep
enough to flood the battery pack strapped to my belt. They
died later, after the trip was over and would not accept a
charge.

Maybe the newer rechargeables are more water resistant?
I was using old technology rechargeables. I'm sure the newer
ones are better. Anyone tried the newer rechargeables in
a water environment?

I've used non rechargeable lithium batteries also. Their biggest
advantage was the long shelf life. Expensive though. Lithium ion
rechargeables might be the best way to go if they are waterproof.

xcathodex, do you know how waterproof the newer rechargeables
are? If they can withstand getting wet, I may want to switch over
to them. But I would still keep alkalines around for back up. Having
to continuously buy alkalines is a hassle at times. If any of you have
ever arrived at a cave to discover you were out of batteries, then you
can relate to running out when you least expected it.
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Postby YuccaPatrol » Dec 18, 2007 9:11 am

I keep some alkalines in my first aid kit so that I don't have to recharge my emergency batteries. The only other use I have for an alkaline battery is in the smoke detectors at home.
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Postby NZcaver » Dec 18, 2007 9:49 am

tncaver wrote:One reason I haven't been using rechargeable batteries is because they died after getting wet. I tried them in several caves and discovered they were fine in dry caves but they died every time I went in caves where the water was deep enough to flood the battery pack trapped to my belt.

Interesting. Occasionally some of my rechargeables have got wet, but I haven't noticed that factor affecting their charge. It's certainly possible, though. Did your wet batteries swell up, corrode, or change form in any other way?

A small suggestion for your situation might be to modify or replace your belt-mounted battery pack with one that is waterproof! Most of the older Petzl headlamps had them like that, but I see they don't bother waterproofing some of the newer belt-pack/neck pouch models. The design priority with those is to keep the batteries warm tucked away inside your clothing when you're in sub-freezing temperatures. Personally for caving, I've always preferred to avoid belt packs with wires strung around me (other than when occasionally using my carbide ceiling burner and generator). But to each their own.
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Postby Jeff Bartlett » Dec 18, 2007 10:40 am

tncaver wrote:xcathodex, do you know how waterproof the newer rechargeables are? If they can withstand getting wet, I may want to switch over to them. But I would still keep alkalines around for back up. Having to continuously buy alkalines is a hassle at times. If any of you have ever arrived at a cave to discover you were out of batteries, then you can relate to running out when you least expected it.


ironically, my cost assumptions in the original post are very optimistic about the purchase price of alkalines, presuming that people ONLY buy the cheapest available alkalines in bulk - when i know everybody has realized last minute that they grabbed a dead set or didn't grab enough, and ended up overpaying at some podunk gas station on the way to the cave =)

as for waterproofness of the new rechargeables, i will say that i lost a set by leaving them in the battery pack of my Apex for about a week. this is before i realized that the battery pack of the Apex is by no means waterproof, and that you basically need to pop it open and dry it (and its contents) out after any trip where you went NEAR water. did they die because they got wet, or because they remained wet for a prolonged period? i have no idea. 2 of them still took a charge, but the problem was that they had actually started to rust, and the black ring around the positive terminals were soggy and loose. i didn't feel safe using them.
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Postby tncaver » Dec 18, 2007 11:05 am

Fortunately I no longer use the light requiring the belt style
battery pack. The wet battery issue may be less important
now because of that. However, I was still curious to know
how well the newer technology rechargeables hold up when
an occasional dunking occurs.

Keep in mind that the rechargeables I used were older
technology. They did not swell up after getting wet. They
simply would not hold a charge.
I'll have to buy some of these new type rechargeables and
a charger and give them a try. xcathodex has convinced
me they are worth a try. I suspect they will produce a brighter
light from my LEDs and maybe stay bright longer as well.
Thank you xcathodex for your informative posts.
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Re: why not rechargeables?

Postby driggs » Dec 18, 2007 4:27 pm

xcathodex wrote:now your turn. why on earth wouldn't we all be using rechargeables? i feel like i'm missing something.


Because NiMH cells are 1.2V and most devices expect 1.5V per cell. The result of this is that devices either don't work, or work at a reduced "output" (dimmer light, shorter runtime, etc). There are exceptions, of course, for example the PT Apex and Fenix lights which were designed up front to handle these cells, and happen to be in applications where a NiMH's properties (current draw?) seem to perform better than alkaline cells. Other devices, like my Garmin GPS, which will work with NiMH cells, has a much shorter battery life on them and may be less sensitive on them.

Why don't we have 1.5V NiMH cells??

The self-discharge rate also makes them a very poor choice (in my opinion) for my use in caving. Only my backup lights use AA cells (rechargeable Li-Ion that lasts forever on my primary), and backup lights rarely get used. Their purpose is to sit there until they are needed. Sometimes that means that weeks or months go by without them being used, or only used very lightly. When my primary dies, I don't want to take any chances that my backup has only 50% charge because it's been in my pack for a month, and I don't want to charge 12 AA cells the day before every caving trip.
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Re: why not rechargeables?

Postby Squirrel Girl » Dec 18, 2007 6:22 pm

driggs wrote:Their purpose is to sit there until they are needed. Sometimes that means that weeks or months go by without them being used, or only used very lightly. When my primary dies, I don't want to take any chances that my backup has only 50% charge because it's been in my pack for a month, and I don't want to charge 12 AA cells the day before every caving trip.
Hybrids NiMHs pretty much solve that problem. Though, I think there are other issues.
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Postby Squirrel Girl » Dec 18, 2007 6:25 pm

So what about rechargeable Li-ion AAs?

e.g., http://www.batteryspace.com/index.asp?P ... rodID=1336
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Postby Jeff Bartlett » Dec 18, 2007 6:40 pm

Squirrel Girl wrote:So what about rechargeable Li-ion AAs?

e.g., http://www.batteryspace.com/index.asp?P ... rodID=1336


i don't know much about these products, but the one you linked to isn't appropriate for use in AA-based devices:

14500 cell has same size as an AA size battery, but has 3 times higher voltage.
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Postby fuzzy-hair-man » Dec 18, 2007 6:50 pm

Squirrel Girl wrote:So what about rechargeable Li-ion AAs?

e.g., http://www.batteryspace.com/index.asp?P ... rodID=1336


Li Ions (3.7V) have a different voltage to alkalines(1.5V) or NiCD/NiMH(1.2V) batteries.

So using Li Ions without knowing something about your lamp could ruin it. But the regulation circuits in some lamps are reasonably tolerant of high voltages (for instance I read about a guy putting a Li Ion pack on his Apex with no other modifications I can't remeber the voltage though check the Apex thread if interested) the other issue is that Li Ions need to be protected by some circuitry (the one you link to doesn't have it) otherwise the battery can be damaged or explode. :flammable:

Others know more..
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Re: why not rechargeables?

Postby arkcaver » Dec 19, 2007 8:58 am

driggs wrote:
xcathodex wrote:now your turn. why on earth wouldn't we all be using rechargeables? i feel like i'm missing something.


Because NiMH cells are 1.2V and most devices expect 1.5V per cell. The result of this is that devices either don't work, or work at a reduced "output" (dimmer light, shorter runtime, etc).


Umm, not really. That is a very common misconception about Alkalines vs. NimHs. It is true that Alkalines have a higher INITIAL voltage, but it doesn't last long. These charts shows the voltage drop in alkalines. If your light has a 1amp drain then your alkalines are at 1.2 volts (the same as NiMHs) in about 10 minutes. This is why the good old non-led Petzl, without voltage regulators, are very bright for about 15 minutes, then get dim very quickly and remain so for another 2 hours.

NiMHs, on the other hand, will hold their 1.2 volts for most of the charge as seen in one of the charts farther down the pdf. So while your light isn't as bright as the initial brightness from alkalines, it will stay as bright as the alkaline light at the 10-15 minute mark.

So in most non-regulated cave lights you will get more useable light from NiMHs than from Alkalines. They won't start off as bright, but you'll be able to see from them a lot longer than from Alkalines.

Voltage regulators are the way to handle this problem. I have a Willy Hunt Easter Seals light that has 5AA batteries in it. It keeps a constant voltage (approx 1.5 volts) throught the lifetime of the cells, but it doesn't work as well on NiMHs because of the lower voltage. The Apex and Fenix lights were designed so that their voltage regulators could handle Alkalines, NiMHs, and Lithiums (which can have a high initial voltage spike, sometimes as much as 1.7 volts).
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Re: why not rechargeables?

Postby Squirrel Girl » Dec 19, 2007 11:09 am

arkcaver wrote:
driggs wrote:
xcathodex wrote:now your turn. why on earth wouldn't we all be using rechargeables? i feel like i'm missing something.


Because NiMH cells are 1.2V and most devices expect 1.5V per cell. The result of this is that devices either don't work, or work at a reduced "output" (dimmer light, shorter runtime, etc).


Umm, not really. That is a very common misconception about Alkalines vs. NimHs. It is true that Alkalines have a higher INITIAL voltage, but it doesn't last long. These charts shows the voltage drop in alkalines. If your light has a 1amp drain then your alkalines are at 1.2 volts (the same as NiMHs) in about 10 minutes.
I've read that elsewhere, too. I'm not an expert at all on this, but I read it yesterday on another website that seemed trustworthy.
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Postby Teresa » Dec 19, 2007 11:49 pm

I've NEVER had standard batteries in my digital cameras. Always NimHs. You'd think that if anything would drain batts, it would be camera flashes. They last much longer than standard alkalines in the camera. The secret to NimHs, is to get high amperage batts-- at least 2500 of what ever sort of ameperage they pack into those things. I've seen AAs with up to 3200 mah (I think this is milliamp hours, but I'm no electronics guru.) The higher this number, the longer they last.

I've always used them in my small tape recorder, and other electronics. Don't have any in my LED lights, because I have a virtually free and inexhaustible supply of AAAs. When and if that supply dries up, I go looking for NimH AAAs.

BTW, they've gone through the laundry and into the drink with no ill effects that I can tell. Just as you wouldn't leave a cardboard wrapped AA in standing water for hours and hours, they aren't waterproof-- but I can't say they are any worse than off the shelf alkalines in that regard. I've had them go dead, but never corrode and take a Minimag with them...which has happened to me twice.
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Postby David Grimes » Dec 20, 2007 1:36 am

The most MaH I have found in a AAA is 900 which really is not much. I modify most of my lights so I generally use homemade battery supplies so it is not really a problem but with most of my stock LED lights that use AAA the alkalines generally last longer which is not really a big factor if they are not your main lights but LED's generally don't provide a great long distance beam of light and one with a half dead battery really doesn't.

I use nothing but LED's but I have had better luck with disposable batteries but maybe I just need to buy better quality rechargeable.
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Postby Mark620 » Dec 24, 2007 12:28 pm

A few things about the Li-ion batteries:
They are 3.6 or 3.7V, if they are over discharged or heated to over 130F* they will catch fire or explode...if they are damaged they will do the same.

There are 2 types Protected and unprotected.

Protected batteries have a circuit that controls the charge rate, the discharge rate and the cut-off! Thats right when the battery drops to a certain voltage as set by the protection circuit you get NO MORE POWER, They cut off and cant be used again until they are recharged.

Unprotected Li-ions - DO NOT USE THEM, unless you do not mind having a fire or explosion happen on your body while caving...or burn your house down while recharging...

There is a new Li-ion out there - it has a hard steel casing to keep it from being damaged...

* it does not matter how the battery gets to this temperature!

Here is a link about one incidence...
http://www.candlepowerforums.com/vb/sho ... p?t=183467
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