Will rechargable batteries hinder peformance?

[Davidgojr]

I just had a quick question. I recently ordered a 15mW laser and I was wondering if using NiMH Rechargables will hurt the performance of the laser. Obviously, NiMH AAA batteries have a lower voltage rating that a standard alkaline battery. (1.2 v as opposed to 1.5) It is also my understanding, however that laser output is more directly related to crystal efficiency than anything else. Will using rechargables hurt the power output?

 

[balazer]

Alkaline batteries start at 1.5 V, but they drop to 1.3 pretty quickly, and then make a steady decline to 0.9 or 0.8 V. Unless your device has an unusually low cut-off voltage or significantly different behavior for brand new alkalines compared to slightly used alkalines, you won't notice any difference using NiMH cells.

 

[ghart999]

Are lithium the ultimate way to go?

 

[bootleg2go]

I agree with david, NiMH are the best way to go. The alkaline may give just a moment or two of higher output, but after that the voltage will continuosly fall, but with MiMH the output will remain more constant as the battery drains.
I would not choose lithium over alkaline as they're pretty expensive. If you could find lithium-ion batteries in the cell size you need, that would work great.

Jack

 

[nemul]

but lithium-ion mostly are v3.6-3.7 and v4.0-4.2 hot off the charger

 

[Corona]

The lower terminal voltage of NiMH AAAs can lead to unsatisfactory performance - all the 110 type pointers I have seen so far have an LD driver structure that places 2 transistors in series with the LD. This creates a problem because of the addition of the voltage drops across all the components...

LD voltage drop ~1.4 to 1.8V
Transistor voltage drop ~ 0.4 to 0.6VDC

Worst case, 1.8 + 0.6 + 0.6 = 3.0V. With fully charged NiMH batteries (at 2.4-2.5V), there isn't any voltage margin to guarantee that the LD will be driven to full output.

Some of the more successful pointer mods out there address this issue by shorting out one of the transistors - this has to be approached carefully, but when correctly executed, results in a pointer that works well on NiMH cells.

Note that the older 105-type (non APC) pointers have a single pass transistor and don't have this limitation.

 

[balazer]

If low terminal voltage were such a problem, those lights would have lousy performance with alkaline batteries also.

 

[Corona]

Balaser, here are the facts.

NiMH fully charged are ~1.25V, so 2 in series = 2.5V

Alkaline cells are 1.5V, so 2 in series = 3V

500mV is a significant difference in terminal voltage, and this results in "lousy performance" with NiMH cells in these pointers, unless modded properly.

BTW I'm a DC power design engineer with 20+ years experience, am familiar with all kinds of battery chemistries, and have designed pointer mods from a technical perspective - so I know what I'm talking about here.

 

[Sim-0]

Hey Corona, what do you know about rechargeable alkaline (RAM) batteries ?

It seems they dont last as many cycles as NiMH/NiCd but they are 1.5v.

I was wondering if they can be charged OK on a computerised R/C type charger (Great Planes Triton). It can handle LiION, Pb, NiCd and NiMH and many charge parameters can be adjusted.

 

[Pixel]

Balaser, here are the facts.

NiMH fully charged are ~1.25V, so 2 in series = 2.5V

Alkaline cells are 1.5V, so 2 in series = 3V

500mV is a significant difference in terminal voltage, and this results in "lousy performance" with NiMH cells in these pointers, unless modded properly.

BTW I'm a DC power design engineer with 20+ years experience, am familiar with all kinds of battery chemistries, and have designed pointer mods from a technical perspective - so I know what I'm talking about here.

All NiMH brands I have, when fully charged are ~1.45V. But even when they go down bellow 1.2V I can't see any difference in laser brightness. And I am using power-meter for the comparision. I own four green laser pointers and still have to see any example when the alkaline batts. produce more performance than NiMH. NiMH and especially 1000mAh models are the best batteries for dpss'es in my point of view.
Maybe the 110 model, you speak about is such a poor case, but I still didn't heard any complains regarding this.

 

[balazer]

Balaser, here are the facts.

NiMH fully charged are ~1.25V, so 2 in series = 2.5V

Alkaline cells are 1.5V, so 2 in series = 3V

500mV is a significant difference in terminal voltage, and this results in "lousy performance" with NiMH cells in these pointers, unless modded properly.

BTW I'm a DC power design engineer with 20+ years experience, am familiar with all kinds of battery chemistries, and have designed pointer mods from a technical perspective - so I know what I'm talking about here.

I believe you. But isn't it also the case that alkaline batteries spend most of their life below 1.25 V or so? To use all the energy in an alkaline effectively, you need to run them down to 1 V or lower.

 

[Corona]

Sorry guys, I was a little testy there. That wasn't right and I apologize!

It comes down to this: component tolerance variations and "tolerance buildup" among many thousands of assemblies will result in some marginal assemblies, and the more corners are cut by the makers (and the more pressure they are under to limit the driver boards' current adjustment range), the more units we will see that fail to deliver full power over the battery's discharge range. My circuit analysis of a couple 110 APC driver boards (Vital's and AltasNova's) shows that they are intentionally designed to make it easy for the manufacturer to cripple the adjustment range, and to do this a number of ways.

Some boards will happen to have transistors with higher gain, for example, and will allow slightly more LD current (with a given, design-limited base current). Some transistors will have lower saturation voltages, and work better at lower voltages. Again, 105s were the "early days" of greenies and the design was pretty wide open. 110s are better by virtue of the APC circuit, but the clever little design crippling is really a problem for modders. This is not going to get any better of course...

It is not always so bad that they have limited these designs to "only" 300-350mA, for example. The stock LDs will suffer short lifetimes when the current is cranked above that.

If you have a 110 that responded well to a pot mod and works with NiMH, you have one with better parts, an earlier, less-crippled design, or are just plain lucky - be happy about that.

Anyway, when battery voltages are specified, there is a "loaded" voltage and a "open circuit" (unloaded) voltage. Yes freshly baked NiMH have an open-circuit voltage near 1.5V - but toss a little load on them and they will drop off. Bottom line there is that the operating range (discharge curve) of NiMHs is a little lower overall.

I haven't seen all that many pointers, but the ones I have seen did not adjust as high (or respond to pot mods at all) on NiMH as on Alkaline cells, and after "fixing" the design, this problem went away.

 

[balazer]

Alkaline and NiMH discharge plots that I've seen show the NiMH cells spending most of their life at a higher voltage than the alkaline cells.

 

[tron3]

Hey Corona, what do you know about rechargeable alkaline (RAM) batteries ?

It seems they dont last as many cycles as NiMH/NiCd but they are 1.5v.

I did a little reading up on them. If you nearly drain them before recharging, they last about 300 charges. If you recharge frequently, they last up to 1000 charges. They come fully charged and have a shelf life of 5+ years. Compare to NiCad, or NiMH that drain much quicker just sitting on the shelf. Plus you have to charge them before 1st use. I want to switch over to them when my current stock of batteries is gone.

As far as AA's go, I'd find a good internet source to buy the Lithium ones in bulk. They last up to 7 times longer! If not, Energizer e2 seems to last twice as long as regular Alkalines. Nice compromise.

 

[nero_design]

I read some of the replied above and I can only offer my own opinion and experience with lasers and batteries.

For the green lasers, I've tried a lot of different brands. Something I discovered with NiHi batteries is that they have a 'constant discharge curve'. This means I simply won't use them with a green diode laser. I prefer the better brands of alkaline etc. or, preferably, lithiums. If you own a digital camera that also uses AAA NiHi batteries, then it probably makes sense to want to use these for your lasers.

Some battery brands are much better for lasers than others. That comment really isn't debatable. They ALL tend to output equally for the first few moments and only the Energizer E2s and Duracel Pro (not available to the general public) seem to hold the same charge for a great deal of time longer. Cheaper or 'standard' alkalines just don't have the grunt. I highly recommend the Energizer E2 batteries. They are available in both Lithium (twice the price - comes in a blue packet) or standard E2. The Standard E2 batteries from Energizer performs virtually the same as the Lithium E2 batteries so save your money and buy the cheaper of the two. I've done some comparative tests and found no difference at all. The Lithiums are less prone to leakage when stored in difficult conditions though. The output is long and constant until the batteries have been expended by 40%. This takes a little while to do. Sure, rechargables will save you a few bucks but most people using Energizer E2s have claimed that they get the brightest constant output for the longest duration of time with these batteries. I'm of the same opinion myself and use the Standard E2s with all my green lasers now. I have a spare pack of the E2 Lithiums but there simply isn't a visible difference in output other than a slightly longer battery life. But not enough extra life to make me chosoe the E2 Lithiums over the regular E2s.

/Just my thoughts on the matter.

 

[Davidgojr]

Thanks for all the replies! It seems though that there is no complete consensus as to the difference they make. I've read all the posts and everyone seems to have had different experiences. I have since received both my 15mW and my 90mW lasers. I plan to try doing some laser experiments in which I compare the results of alkaline vs the NiMH rechargables. Until then, if anyone has any more thoughts on the matter, please share!

 

[Databyter]

Personally I am a big fan of NiMH because of the cost factor. Just get some good quality >2300 ma nexell or powerx and it should be fine.

If they drained in a poor way they wouldn't be the battery of choice for some very power hungry devices such as digital cameras. They have good useable current until they are dead in my experience.

It goes without saying that like any other type you need to buy one of the top brands and definitly high capacity.

I use duracells in mine though. They last forever for the low power lasers I currently have and although I use them a few times a day the duration I have them on is low.

I'm interested in your test for the hungrier type of laser because I'm getting one eventually and don't like buying batteries too often.

 

[Athoul]

Well as to my knowledge the AAA NiMH batteries don't come in >2300mah, the max that I have seen for AAA is 1000mah. Maybe you were thinking of AA?

The E2 will have a greater then 1.2v output for longer then alkalines, and thus is where you see the difference. NiMH typically put out ~1.2V not 1.5v. However Alkaline and even E2's will drop to lower then 1.2V after a relativly short period of use. The thing here is that Alkalines will drop relativly fast from ~1.2 to about ~0.8V and then just die out. E2's will hang on longer to ~1.5v before dropping steadily to ~0.8v. Now NiMH will last longer around ~1.2V in fact longer then Alkalines or E2's(but lacks the initial 1.5v that these cells put out). Also once they begin to die they have a steady discharge rate and will tapper right off. Over all though you will get longer ~1.2-1.0v with NiMH.

I guess the big thing here is the initial 1.5v power, and so e2's would be the best for that..but when looking at the overall battery life, most of its life is spent under 1.2v anyways.

The ideal of course would be rechargable Li-Ion batteries ... could always dismantle a Li-Ion battery pack with AAA cells in it, then use the pack as the charger..

My 2 1/2 cents..

 

[Databyter]

Your right Athoul I was using aa's capacity numbers. Oops maybe no one will notice...

 

[Athoul]

No prob, it happens

Just a question since this is a battery thread.

I has posted above that you could dismantle a Li-Ion battery pack that contains AAA size cells, this due to that I have looked and to my knowledge there are no AAA Li-Ion rechargable batteries as OEM products. Are there any anywhere made by anyone as OEM?