# Nicd vs Nimh Question



## 5Sport (Feb 28, 2012)

I was looking at the new Streamlight SL20L (LED) and I have the choice between either Nicad or Nimh batteries (same price). My vendor sent me this info: 
*As is true about many things in the life, there’s a lot of confusion and misinformation about NiCd and NiMH technologies. Let’s see if we can clarify things a little for you.*
*The advantage of NiMH cells is that for a given cell size, they have a higher capacity compared to NiCd cells. That means that many devices will work longer using NiMH cells. In addition, because they do not contain cadmium, they are more environmentally friendly.*
*The disadvantage of NiMH cells is that they usually have a much higher internal impedance. That means that if you try to draw a lot of current from NiMH cells, they will drop excessively in voltage which can cause poor performance or the device they are powering to shut down. At SR, we only produce premium NiMH packs with low internal impedance NiMH cells. Although they aren’t as low as our NiCd cells, they are close enough that you shouldn’t see a difference in normal applications.*
*NiMH cells are a little heavier than the same physical size NiCd cell. Our 2400 Max Series NiCd cell is SubC in size, weighs about 2 oz. and has a capacity of about 2400 mah. Our SubC size 3400H Series NiMH cell has a capacity of over 3400 mah, but weighs about 2.3oz., 15% heavier.*
*Don’t expect the same life span from a NiMH cell compared to a NiCd cell. Our experience has been that you will need to replace NiMH packs about twice as often as NiCd packs regardless of who made the packs. Also, be careful about temperature extremes with NiMH cells as they tend to lose their charge much more quickly than NiCd cells in very hot or cold climates. They are happiest at any room temperatures just like you.*
*Finally, don’t expect to charge a NiMH pack today and then use it a week or two from now as NiMH cells lose their charge two or three times faster than NiCd cells do. You also shouldn’t fast charge a NiMH cell at as high a charge rate as you would a NiCd cell. That’s because of the higher internal impedance.

*So my question is, is this true? The light will sit in a charger in my car most of the time and will see limited use. Is the Nicd better for this application. Thanks


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## StarHalo (Feb 28, 2012)

Nope, the guy has it pretty much 180 degrees wrong and is straight up lying to you. I would find another vendor; even if he thinks he's telling you the truth, he shouldn't be selling flashlights..


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## 5Sport (Feb 28, 2012)

They sell more than flashlights. Guns, etc, but is this coming from Streamlight? If this is incorrect, what is the real story. I did a search, but the info I found was from 2001. I'm thinking technology has come a little way since then. What would be best for my application?


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## StarHalo (Feb 28, 2012)

Just off the top of my head:

- NiMH hold up very well to heavy current draw and can manage output and runtime that alkaline cells can't come close to.

- NiCds self-discharge at a fantastic rate; back in the day, If you didn't use your freshly charged NiCd AA cells within roughly a month, they'd be completely dead. A modern NiMH/Eneloop cell loses maybe 10% of its charge over the course of a year.

- All rechargeable cells have roughly the same extreme temperature handling, worse than lithium primaries and better than alkalines.

I'll let someone who knows more about battery chemistry (and can remember NiCds better) fill in the gaps..


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## 45/70 (Feb 28, 2012)

StarHalo said:


> Nope, the guy has it pretty much 180 degrees wrong



I don't know where you got your info Star, but I'd say that summary is pretty accurate. NiCd cells with the exception of their lower capacity and the need to frequently discharge them rather than "top them off", are superior in all ways mentioned, in my experience.

I'm not too sure about the weight comparison. This has a lot to do with specific cell construction. Also, most (but not all) of the cheap Chinese NiCd cells are crap and are poor for comparative purposes, but then so are most Chinese NiMh cells.

The durability and robustness of NiCd over NiMh cells is why a lot of companies, like Streamlight, still offer NiCd battery packs. They hold up much better than NiMh packs, particularly when over discharged. Over discharging NiCd cells in series isn't good for them either, but frequently doing so with NiMh cells kills them in short order.

Dave


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## 45/70 (Feb 28, 2012)

StarHalo said:


> - NiMH hold up very well to heavy current draw and can manage output and runtime that alkaline cells can't come close to.



Good NiCd cells like Sanyo Cadnica's will provide higher voltage under load than traditional NiMh cells. In fact their performance is close to that of LSD NiMh cells, such as eneloops. It's true, most all quality nickel based rechargeable cells will outperform alkaline cells under heavy current loads. Alkaline cells just aren't cut out for any but light to moderate loads.



> NiCds self-discharge at a fantastic rate



Actually the self discharge rate of NiCd cells is about one third to one half that of traditional NiMh cells. This places them somewhere between traditional NiMh cells and LSD NiMh cells.



> All rechargeable cells have roughly the same extreme temperature handling



IIRC NiCd cells have a bit of an edge at both temperature extremes. They are close here though.

The main reason NiCd cells are disappearing are environmental concerns and their inferior capacity. Proper recycling of NiCd cells would solve the environmental concerns, for the most part. As for the capacity difference, not much can be done here. Still, when you consider that NiCd cells last between 1000 and 2000 cycles, compared to traditional NiMh cell's 300 cycles, this offsets things a bit. All and all though, except for a few advantages, such as better resistance to over discharging in series, LSD NiMh cells are the way of the future for nickel based cells.

Dave


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## StarHalo (Feb 28, 2012)

45/70 said:


> In fact their performance is close to that of LSD NiMh cells



Thank you for pointing that out, I should be more specific - I'm referring exclusively to LSD NiMHs, like Eneloops, as that's really the only NiMH type flashaholics use now.


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## 45/70 (Feb 28, 2012)

True, but as far as battery packs are concerned, most all that I am aware of are traditional NiMh. I think this is partly because sub C and other oddball sizes of cells used in pack making are, so far, only available in the traditional flavor. The other factor may be cost.

Dave


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## StarHalo (Feb 28, 2012)

45/70 said:


> sub C and other oddball sizes of cells used in pack making



Which is what makes it something of a moot point; if you make a flashlight that accepts only your batteries, and no other batteries fit, then there's not much point in touting your battery chemistry. 

Even if they made NiMH packs, I wouldn't buy the light just because it's essentially guaranteed to be obsolete in time. And if that's the only light you have on you in a power outage, good luck recharging it, since just putting in new cells isn't an option..


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## Robin24k (Feb 28, 2012)

Both the NiMH and NiCd are OEM battery packs, right? Streamlight is starting to release NiMH options, which are LSD NiMH and good for 1000 cycles.

While the information you got is not necessarily incorrect, parts of it are outdated and do not apply to modern LSD NiMH batteries. They certainly won't last half as long as NiCd or self-discharge that quickly. I would go with the NiMH option.


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## 5Sport (Feb 28, 2012)

Thanks all, lots on info and I'm still alittle confused. So what you are saying, for my particular application, NIMH is what I want for a light that will sit charging in the trunk of my car with infrequent use?

Yes they are the battery packs from Streamlight.


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## Robin24k (Feb 28, 2012)

Actually, continuous charging is not good for any battery chemistry...


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## 5Sport (Feb 28, 2012)

I realize that, but it is a work light that sits in my car charger. I have others.

So with that in mind, any recommendation as to which one would be better for my application.

Thanks


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## Wrend (Feb 28, 2012)

The perils of bad charging.

If those are your only options, I'd guess go with the NiCds. I think they tend to hold up a little better with continuous overcharging.


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## Bozzlite (Feb 29, 2012)

I have a MagCharger and had an SL20X which both use the same battery pack. 5 half-D cells. Originally they both came with the NiCad pack. I had to replace the pack in the older SL20 twice and the newer MC once. I opted for the NiMh for the MC.

This is just my experience, but the NiMh seems to self discharge at a lower rate than the NiCads. I do not keep them under constant charge, just plug 'em in once every couple of months or so. I would go with the NiMH pack just for the higher mah capacity if nothing else. 

In fact, all the NiCad powered tools I use seem to self discharge rather quickly. Dremel tool, hand held vacuum, 18 volt drill, grass trimmer, etc.


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## SilverFox (Feb 29, 2012)

Hello 5Sport,

Go with the NiMh pack and train yourself to only plug the charger in about once a month. If you can't do this, go with the NiMh pack anyways. Most likely the charger trickle charge is set up for the lower capacity NiCd pack so it will be somewhat gentle on the NiMh pack that has higher capacity. 

It is not good to let the pack charge or trickle charge over extended periods of time. I have a TigerLight in my vehicle and it has a NiMh battery pack. I can go a few months before the self discharge gets to the point where I end up with very limited run time. I charge it up after use and try to remember to charge it once a month. 

Tom


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## 5Sport (Feb 29, 2012)

ok, oposing opinions. Now you guys are screwing with me.


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## hank (Feb 29, 2012)

No, there's a great variety of hardware -- you get opinions based on people's experience, which varies.

To leave in your car trunk, or any emergency kit, get a light that uses nonrechargeable Energizer Lithium (primary) AA or AAA cells, which don't get weak when cold, and last years in storage, and don't leak. They're the only good option for a light you neglect 'til an emergency needs it.

The other thing about NiCd is toxicity. People have died downwind of trash fires where someone had tossed a NiCd battery into the trash; read that long before the Web so no handy link but the risk is easy to confirm. If you don't take stuff to a hazmat waste site, don't buy NiCd.

"Cadmium is readily absorbed by the human body from food or water, but is much less readily excreted, and so becomes concentrated to a high degree in some body tissues. Like mercury, cadmium is highly toxic to humans, typically affecting the kidneys, bones, liver and nervous system. Inhaling fumes of the metal or freshly-formed oxide can cause lung scarring, pneumonia, emphysema, or even death. As a result, it is listed as a characteristic hazardous waste .... The volatility of cadmium, combined with its toxicity .... cadmium vaporizes, forms fine particles suspended in the air, and can poison anyone who breathes in the particles." http://www.freepatentsonline.com/5405588.html


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## MikeAusC (Feb 29, 2012)

Robin24k said:


> Actually, continuous charging is not good for any battery chemistry...



. . . except Lead Acid - for longest life you need to avoid Sulphation by keeping them at 100% charge. 

Stationary batteries in Telepone Exchanges /Central Offices, Radio Sites, Uninterruble Power Supplies etc keep their batteries on Float Charge permanently.


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## Lynx_Arc (Feb 29, 2012)

Trying to equate LSD nimh batteries in SubC variety doesn't work because as far as I know the only way to (possibly) get them is to buy rayovac hybrid C and D cells that supposedly have subC batteries in them. I have found no source of subC LSD Nimh batteries.


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## alpg88 (Feb 29, 2012)

at my work i still have drill that is 10 years old, with nicd cells, sanyo cells, they stil work just as good as they did 10 years ago, not as long thou, but power wise , they have not lost much, nimh otoh don't live more than 3 years, so yea, i agree with the guy, except for capacity, nicd destroy nimh.


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## Robin24k (Feb 29, 2012)

Lynx_Arc said:


> Trying to equate LSD nimh batteries in SubC variety doesn't work because as far as I know the only way to (possibly) get them is to buy rayovac hybrid C and D cells that supposedly have subC batteries in them. I have found no source of subC LSD Nimh batteries.


Streamlight has confirmed to me that the NiMH batteries they are using will retain up to 85% of its charge for a year, which sure sounds like LSD NiMH...


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## Lynx_Arc (Feb 29, 2012)

Robin24k said:


> Streamlight has confirmed to me that the NiMH batteries they are using will retain up to 85% of its charge for a year, which sure sounds like LSD NiMH...


Sounds like it, just have to wait and see if they hold up well or not to the specs given.


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## Robin24k (Feb 29, 2012)

I'll try to do that if I remember. I'm using a regular NiCd pack in my Stinger DS LED, so the NiMH that came with it has been in storage (last charged 11/16/2011). If I don't accidentally use it before 5/16/2012, I'll put it through a runtime test.

Someone will probably need to remind me to do it when it's time to do it though...


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## 5Sport (Mar 12, 2012)

So I got the flashlight today with the NIMH battery. It is smaller than the NICAD batt and there is a rubber sleeve in it to make it fit. It looks similar to the battery in the SL20 that has both the ican bulb and the 3 small LEDS (I don't have one handy to compare though). The instructions say that it is designed to sit in the charger and that it will not overcharge the battery. The instructions say that the red light on the flashlight will flash when charged. This is different than my old SL20 where the red lights stays on constantly.

I guess we will see.


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## Robin24k (Mar 12, 2012)

5Sport said:


> This is different than my old SL20 where the red lights stays on constantly.


With a fast charger, the red LED will flash when the battery is fully charged. With a steady charger, the red LED will not flash. I think that's the reason why you are seeing different behavior.


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## 5Sport (Mar 12, 2012)

How do you tell which charger is which. The ones that came with the FL look the same as the charger that I already have. There are no markings on either of them, and the lights are on the flashlight not the charger


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## dano (Mar 12, 2012)

streamlights newest Nicads are rated at 2400mah for the stick that is used in the new 20l and the 20x/LED. The Nimh that streamlight is using in the 20l and the Stinger is rated at 2200mah.

In real world usage, there wont be much difference. Buy whatever one is available.


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## dano (Mar 12, 2012)

5Sport said:


> How do you tell which charger is which. The ones that came with the FL look the same as the charger that I already have. There are no markings on either of them, and the lights are on the flashlight not the charger



There is no fast charger for the SL. The cradle is the same across the product line, and slow charges. The 20l is somewhat different as it incorporates circuitry in the switch that blinks a built in LED when the light is done, somewhat like a peak detection charger.


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## Robin24k (Mar 12, 2012)

Apologize for the confusion...it's been a while and I thought this was a thread about the Stinger. There is indeed only one charger for the SL-series, which fully charges the battery in 7 hours.


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## CKOD (Mar 13, 2012)

MikeAusC said:


> . . . except Lead Acid - for longest life you need to avoid Sulphation by keeping them at 100% charge.
> 
> Stationary batteries in Telepone Exchanges /Central Offices, Radio Sites, Uninterruble Power Supplies etc keep their batteries on Float Charge permanently.



While I wont disagree, a float charge isnt detrimental to a Lead acid cell, it wont be enough to prevent sulphation long term on its own. Periodic charging to the "cyclic" charge voltage (usually 14.4-14.5 for 12v batteries IIRC) helps extend life beyond what being on float the whole time would provide. But we're drifting here, as lead acid batteries dont belong in small flashlights )


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## 5Sport (Mar 13, 2012)

Ok, this thing has been charging for 24 hours and the red light is still not flashing. Just a steady red.


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## 5Sport (Mar 19, 2012)

Over a week later and now it is blinking. Now that was a long time.


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## Lynx_Arc (Mar 19, 2012)

could have a bad/marginal cell in the pack that took that long to charge completely up.


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## 5Sport (Mar 19, 2012)

Oh that would suck


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