Replace 6x NiCd A's with 2x 18650's?

[Dennis]

Hi,

I have a Surefire 10X with a dead battery pack and I don't want to spend another $80 for a new one with old fashioned NiCD cells. The OEM pack is 6x A size NiCd's (unknown mAh), and I was thinking of replacing them with either:

- A size NiMh's (hard to find nowadays!)
- AA size Eneloops since this light does lots of sitting around (enough mAh/draw?)
- 2x 18650's?

6xA's = 8.4V fully charged which is the same as 2x18650's.

What am I missing here? I am sure there is some fundamental issue, maybe with the incan bulbs? There are definitely going to be charging issues I guess.

Thanks for any help!

Dennis.

 

[R@ndom]

You can get Sanyo 1700 ni-cad's from the battery station. Direct swap and no charging problems. Being ni-cad they will also handle the drain quite well.

 

[Kestrel]

While I am not familiar with the bulb in the 10x (knowing the amperage of that bulb would be helpful), I know that the basic ROP bulbs (for example) use either 6x NiMH (Eneloops work great) or 2x 18650 pretty much interchangeably, no real voltage issues.

• NiMH under medium-heavy load = 6x1.2 = 7.2, and NiCads should be about the same
• 18650 LiIon under same = 2x3.7 = 7.4

Pretty much the same either way, and I'm guessing that the SF bulb has plenty of voltage headroom on the top end. I do know that NiCads handle high drain rates better than NiMH or LiIon. If you can ascertain that NiMH / LiIons are compatible with the (probably high) drain rate in the 10x, my two lumens, I'd prefer Eneloop NiMH's or AW LiIons for higher capacity and little-to-no self-discharge.

If the drain rate is uncomfortably high, IMR LiIon cells would be just the ticket and your voltage should still be in the ballpark. IMR 26500's would be great, will they fit width-wise?

Oh, and charging, definitely an issue - NiCads are far more robust with regards to charging abuse than NiMH, and both proposed replacements (LiIon in particular) would require a different charger.


I'm guessing someone who knows more than me will be along shortly. Good luck,

Edit: Holy cow, you've been on CPF since January 2001?!
I feel sheepish about being presumptuous enough to offer advice to such a veteran.

 

[Dennis]

Haha, been on since 2001 and a flashaholic since my first SF in 1991 but my minor modding days are long gone and it's generally just easier to buy good stuff! However, my 10x still holds up against my Olight M30 and Malkoff super drop-ins so I might as well try and keep it up to date!

Hmm, I didn't think about the OEM NiCd charger not being able to handle NiMh batts. It's been awhile I guess...

Thanks for the info Kestrel!

Dennis.

 

[45/70]

What am I missing here?

As Kestrel pointed out, probably not much!

All I can say is that the better NiCd cells, which I'm sure SF uses, are much more tolerant of all kinds of abuse than Li-Ion or NiMH. I think that's why some flashlight, and especially cordless tool makers, still use them. I wouldn't be suprised if the NiCds in the pack used couldn't give IMR's a run for their money, as far as current delivery either. In the end, I'm betting NiCd's would outlast either, as well.

If I were you, I'd stick with the NiCd's. The other two may work better for the first few weeks, but once you run the pack down too low a few times, reverse charge a couple cells, or forget to charge them for a while, the contest will be over.

Now if your wanting to hotrod the 10X, that's different.

Dave

 

[flatline]

All I can say is that the better NiCd cells, which I'm sure SF uses, are much more tolerant of all kinds of abuse than Li-Ion or NiMH. I think that's why some flashlight, and especially cordless tool makers, still use them.

Edit: my apology to 45/70 for accidentally including the first line of my reply in his quote block rather than after it. Fixed now.

NiCads are actually less forgiving than other chemistries.

If I remember correctly, NiCad was preferred for power tools because their internal resistance doesn't increase as the cell ages. This means that even when the cell has diminished capacity, it's still capable of delivering what capacity it has. NiMh does not have this property, neither does the standard Li-ion chemistry. That's why power tools stayed with NiCad. However, the Manganese chemistry does not increase it's internal resistance as it ages which is why you're seeing NiCad being replaced by Lithium cells now. The Lithium Manganese cells don't have the energy density as the regular Li-ion, but the two chemistries can be mixed to increase the capacity of the cell and still keep internal resistance to acceptable levels over the life of the cell.

Hope I've remembered this correctly. Been a while since I read through the material at Battery University.

--flatline

 

[fivemega]

Hi,

I have a Surefire 10X with a dead battery pack and I don't want to spend another $80 for a new one with old fashioned NiCD cells. The OEM pack is 6x A size NiCd's (unknown mAh), and I was thinking of replacing them with either:

- A size NiMh's (hard to find nowadays!)
- AA size Eneloops since this light does lots of sitting around (enough mAh/draw?)
- 2x 18650's?

6xA's = 8.4V fully charged which is the same as 2x18650's.

What am I missing here? I am sure there is some fundamental issue, maybe with the incan bulbs? There are definitely going to be charging issues I guess.

Thanks for any help!

Dennis.

The OEM pack is 6x A size NiCd's (50mm long, 17mm diameter) and 18XXX won't fit physically. Even if they fit, protected type won't power up with first click and IMRs will severely overdrive the Hi bulb.
5.5 Amp current draw is too much for Eneloops and light output will go yellow quickly.
The last choice is 2S/2P protected 17670
And the most important issue for all above configuration is charging.

 

[45/70]

Originally Posted by 45/70
NiCads are actually less forgiving than other chemistries.

All I can say is that the better NiCd cells, which I'm sure SF uses, are much more tolerant of all kinds of abuse than Li-Ion or NiMH. I think that's why some flashlight, and especially cordless tool makers, still use them.

flatline, fix the quote! :hairpull:

I certainly didn't say that first line, and couldn't disagree more!

Dave

 

[flatline]

flatline, fix the quote! :hairpull:

I certainly didn't say that first line, and couldn't disagree more!

Dave

Sorry about that. I've fixed my original post.

--flatline

 

[45/70]

Thanks for the fix, flatline. :thumbsup:

Now, on to the business at hand.

NiCads are actually less forgiving than other chemistries.

I'm not sure what you mean here. What I do know is that in series applications NiMH and IMR chemistry cells suffer damage when discharged below a certain voltage level. This is not true of NiCds. Discharging a NiCd to zero volts has no ill effect, and can actually be beneficial to the cell.

Subjecting a NiMH cell to a reverse charge condition in a series application causes permanent damage to the cell. I'm not sure what happens to an IMR cell in a reverse charge condition, but I'm sure it's not good for the cell. While a reverse charge condition is not good for NiCd's, the ill effects are usually minimal, especially if the situation is stopped in time, eg. you notice your light gets dim, and you shut it off.

Again, as far as durability is concerned, I think the NiCd is superior. That's not to say they are better performing, but can sustain more abuse and last longer. I've seen this in my personal experince with NiMH vs. NiCd. I don't have any experience with the IMR's, as I much prefer the LiCo's for their much better power to weight/volume ratio in the 1-1.5C applications I use them in.

Dave