multiple lasers on single battery

I use a several pretty standard green laser pointers for work. I use them to paint tracking points on far away surfaces when filming for visual effects. However, they require AAA batteries which die at random times and basically don't work at all in colder weather. Also, replacing the batteries in a hurry is a pain in the butt.

What I'd like to do is build my own rig, where I have several lasers hooked up to a single power source. So here are my questions...

1) Where is the best place to buy a trustworthy green laser diode with the below specs...
- 532nm
- Class IIIA
- 5mW max output
- IR sheild/filter
- built in current regulator/controller (is this what it's called?)
- sharp, clean dot projection

2) What's the best battery to use? I was thinking something like a 12V RC LiPo, or perhaps just a 12V Lithium Ion of some sort, but I should be rechargable and robust?

3) What's the best configuration to hook up several lasers to the single battery? In series, in parallel? How many can I hook up to one battery? I expect I'll need to build a proper circuit with resisters, etc, but I'm a newbie to this so looking for some help here. Ideally I'd like to build a rig where I have about 6 lasers connected to a single battery, if possible. I was thinking something like the attached schematic?

4) If I'm over complicating this, I'm OPEN to suggestions. Perhaps something as simply as a AAA to DC power source conversion kit?

In general - if you put bateries in series you increase voltage, if in parallel you increase current draw possibility. You might combine them almost as you like, but is it worth? There exist high capacity lead gel accumulators available in 6 V and 12 V, what I'm seeing in store next to the place where I work. A bit heavy but this might be what you are looking for.

acer4069 said:

I use a several pretty standard green laser pointers for work. I use them to paint tracking points on far away surfaces when filming for visual effects. However, they require AAA batteries which die at random times and basically don't work at all in colder weather. Also, replacing the batteries in a hurry is a pain in the butt.

What I'd like to do is build my own rig, where I have several lasers hooked up to a single power source. So here are my questions...

1) Where is the best place to buy a trustworthy green laser diode with the below specs...
- 532nm
- Class IIIA
- 5mW max output
- IR sheild/filter
- built in current regulator/controller (is this what it's called?)
- sharp, clean dot projection

2) What's the best battery to use? I was thinking something like a 12V RC LiPo, or perhaps just a 12V Lithium Ion of some sort, but I should be rechargable and robust?

3) What's the best configuration to hook up several lasers to the single battery? In series, in parallel? How many can I hook up to one battery? I expect I'll need to build a proper circuit with resisters, etc, but I'm a newbie to this so looking for some help here. Ideally I'd like to build a rig where I have about 6 lasers connected to a single battery, if possible. I was thinking something like the attached schematic?

4) If I'm over complicating this, I'm OPEN to suggestions. Perhaps something as simply as a AAA to DC power source conversion kit?

Click to expand...

Have you tried the Energizer (Or is it duracell?) Lithium batteries? They last ages, although they are more pricey.

The issue with the cold may be a combination of cheap batteries and the fact that you're using a 532nm DPSS laser. DPSS lasers do not like operating outside of their "sweet spot" when it comes to temperature. Too hot or too cold and they'll stop working/become erratic.

1) Look for a 520nm green laser, no need for an IR filter and the cold doesn't bother them.

2) That depends on what you get? If you're using pointers they'll only accept specific batteries. If you're just using bare modules and hooking them up yourself then things become more flexible. I'd go for 3.7V Lithium batteries (not the Duracell/Energizer ones). Size/configuration will depend on how many lasers you want to run and what type (i.e. 520nm/532nm?).

3) They'd be connected to the battery in parallel. No need for resistors or anything like that, assuming you get modules with attached laser diode drivers (your "current regulator referred to in point 1). For 6x 5mW lasers a single 18650 would probably work, or 2-3 in parallel if you'd like longer run times. 532nm modules are available that run at the 3.7V of a single lithium cell. You may be able to find 520nm modules that operate at those voltages too. I have a couple of boost drivers here that'll drive a 520nm diode just fine at 3V input with ~7.5V output. (520nm diodes need about 7.5V, vs the 1.8V of a DPSS pump diode).

4) AAAs are already DC...? You can stack multiple in parallel for longer run times/higher currents. If you need more voltage you can add them in series. Lithium batteries do offer better capacity and higher currents, so you could achieve the same using less batteries.

I use only Energizer lithium for my EVO (eats 2 AA). They are good but not rechargeable (I have not tried even there are methods how to charge alkalines) and expensive 4 cost me 205 CZK this is around 8.60 EUR (might be cheaper in some eshop). The interesting is they have 1.8 V and drop to 1.5 when load is attached. And last long as hell and are able to deliver highest current (according to test I saw on candlepowerforums I guess). The best experience with them if speaking about AA. But even they are affected by low temperatures (own experience). I think this might not be an issue for Pb gells as these might be designed more for lower temperatures, however I did not tried them yet. But I keep them on mind for some projects where is needed 230 V AC (I have convertor from 12 V DC) - the issue is if they are able deliver high current for reasonable time.

BTW: When the Energizers are empty for laser I use them for devices not requiring high currents - like remote controls, wall clock etc...

Radim said:

I use only Energizer lithium for my EVO (eats 2 AA). They are good but not rechargeable (I have not tried even if there are methods how to charge alkalines) and expensive 4 cost me 205 CZK this is around 8.60 EUR (might be cheaper in some eshop). The interesting is they have 1.8 V and drop to 1.5 when load is attached. And last long as hell and are able to deliver highest current (according to test I saw on candlepowerforums I guess). The best experience with them if speaking about AA. But even they are affected by low temperatures (own experience). I think this might not be an issue for Pb gells as these might be designed more for lower temperatures, however I did not tried them yet. But I keep them on mind for some projects where is needed 230 V AC (I have convertor from 12 V DC) - the issue is if they are able deliver high current for reasonable time.

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Can't recharge the AA/AAA lithiums as they are a primary cell (chemistry is Li-FeS2).

They're good, but yes, rather pricey. Last pack of 4 I bought was $14 I think.

Problem with Pb batteries is the size and weight of them. Lithium are smaller for a given capacity and discharge rate (considerably higher energy density in Wh/kg). Lithium batteries are capable of more cycles than lead acid too.

diachi said:

Can't recharge the AA/AAA lithiums (almost 100% sure it's just a regular lithium with a voltage regulator to step down to 1.5V).

They're good, but yes, rather pricey. Last pack of 4 I bought was $14 I think.

Problem with Pb batteries is the size and weight of them. Lithium are smaller for a given capacity and discharge rate (considerably higher density in Wh/kg). Lithium batteries are capable of more cycles than lead acid too.

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Exactly. However they were not very large for like 6 Ah at 12 V (I guess, I might look tomorrow). Regarding recharging alkalines I've read that there is needed to be really low current for recharging, but I did not tried that and do not recommend. The article looked quite trustworthy. For lithium Energizer it was not mentioned, just for standard alkalines.

Do you know whether Pb gells might be able to do better then lithiums in low temperatures? Like car accumulators do if maintained and charged well.

Radim said:

Exactly. However they were not very large for like 6 Ah at 12 V (I guess, I might look tomorrow). Regarding recharging alkalines I've read that there is needed to be really low current for recharging, but I did not tried that and do not recommend. The article looked quite trustworthy. For lithium Energizer it was not mentioned, just for standard alkalines.

Do you know whether Pb gells might be able to do better then lithiums in low temperatures? Like car accumulators do if maintained and charged well.

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The 12V 6Ah Pb batteries are still rather beefy and heavy, I've got a couple 7Ah ones in the back of my truck, weigh several pounds each and are L5.94xW2.56xH3.66 (all in inches).


Pb gel should perform better than lithium in the cold. Pb gel IIRC has the advantage of not freezing at extreme cold temperatures too (where regular Pb-Acid can), but we're talking -40 sort of temperatures...

diachi said:

The 12V 6Ah Pb batteries are still rather beefy and heavy, I've got a couple 7Ah ones in the back of my truck, weigh several pounds each and are L5.94xW2.56xH3.66 (all in inches).


Pb gel should perform better than lithium in the cold. Pb gel IIRC has the advantage of not freezing at extreme cold temperatures too (where regular Pb-Acid can), but we're talking -40 sort of temperatures...

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Thanks, diachi. Might be option.

It depends if weight is limit for OP.

Great feedback so far, thanks everyone!

I'll look into the 520nm lasers.

As for the batteries, i'm not as concerned about weight as I have a lot of other heavy gear, anyways. Ideally I'd like a batter that could power up to 6 lasers for around 2-3 hours, if possible. I want rechargeable because I could use the lasers as often as twice a week for a few months straight, and I don't want to buy new batteries that often.

Are there any online circuit design apps that anyone would recommend that could help me configure my setup once I select the diodes and battery?

You are welcome. I've never used any app, I always used paper and pen for that. But do not forget suitable drivers for diodes, you cannot just connect them to source directly - they would be burned instantly.

I think what you're asking for seems simple. Here's what I would do -

I'd set up a project box with a couple of 18650's in it, wired in parallel, and then I'd just build a couple of leads that go to the pointers, connecting to 'dummy' battery packs made out of wooden dowels.

I'd also probably use a hacksaw and file to 'slot' the lasers such that the wires can run in and the tailcap can still be screwed on.

Boom, DAYS worth of power. Also, I'd consider having a small warm pack of some sort to store them in so that the Nd:YAG crystals don't get freezing cold and fail to work correctly.

I'd also consider putting on a permanent on/off switch and attaching the lasers to holders of some sort (gooseneck bendable lamp type most likely)

CoryB said:

I think what you're asking for seems simple. Here's what I would do -

I'd set up a project box with a couple of 18650's in it, wired in parallel, and then I'd just build a couple of leads that go to the pointers, connecting to 'dummy' battery packs made out of wooden dowels.

I'd also probably use a hacksaw and file to 'slot' the lasers such that the wires can run in and the tailcap can still be screwed on.

Boom, DAYS worth of power. Also, I'd consider having a small warm pack of some sort to store them in so that the Nd:YAG crystals don't get freezing cold and fail to work correctly.

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Agreed Re: batteries ... However, if OP wants to use these as pointers then I'd suggest just getting pointers that take 18650s ... Then I'd get a half decent 18650 charger that runs off of USB and one of those 10Ah battery packs designed for running/charging USB devices... That gives you A) Lots of use with the 18650 batteries in the lasers. B) The option of recharging those batteries on the go if they happen to die.

If OP just wants bare modules hooked up with leads then yes, get a battery box for a couple 18650s in parallel, put +V and -V wire terminals on them, and hook the modules up in parallel, i.e. +V of modules connected to +V of the battery pack, same for -V.

As for heating the modules to keep the Nd:YAG (pointers use Nd:YVO4 now) warm, it'd be better just to go for some cheap 520nm pointers that wont' care how hot or cold they get (within reason). Also, it's the KTP that's generally most picky about temperature, not YVO4/YAG, although they are affected by any temperature induced wavelength shift of the pump LD, but generally less so.

diachi said:

Agreed Re: batteries ... However, if OP wants to use these as pointers then I'd suggest just getting pointers that take 18650s ... Then I'd get a half decent 18650 charger that runs off of USB and one of those 10Ah battery packs designed for running/charging USB devices... That gives you A) Lots of use with the 18650 batteries in the lasers. B) The option of recharging those batteries on the go if they happen to die.

If OP just wants bare modules hooked up with leads then yes, get a battery box for a couple 18650s in parallel, put +V and -V wire terminals on them, and hook the modules up in parallel, i.e. +V of modules connected to +V of the battery pack, same for -V.

As for heating the modules to keep the Nd:YAG (pointers use Nd:YVO4 now) warm, it'd be better just to go for some cheap 520nm pointers that wont' care how hot or cold they get (within reason). Also, it's the KTP that's generally most picky about temperature, not YVO4/YAG, although they are affected by any temperature induced wavelength shift of the pump LD, but generally less so.

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But... That's TOO EASY. ;-)

Seriously, though, you're right - just buying a couple of new pointers is probably smartest.

OP: My advise is to grab a few of these. Bought a few for gifts, and ended up keeping a couple because they were just so darn good for the $$..

Takes either 1x 16850 or 2x 16340

Military Powerful 5mW 532nm Green Laser Pointer Pen Beam Light Burning Lazer USA

DISCLAIMER: There is pretty much no way the <5mw rating is correct on these. I'd guess more like 30-75mw.

If you use diodes low temperatures are not the issue (if not extreme) as diachi mentioned. Low temperatures affect more the batts - lithiums. They just increase their internal resistance and are not able to deliver higher currents. Own experience. Sometimes they just deliver no current at all... That's why I came up with Pb gels and discussed them with diachi. Depending on diode powers, efficiency and losses on drivers and other stuff you include in circuit you can calculate total required current and compare it with batt/accu pack specs to estimate time. I believe that for something like 6-7 Ah at 12 V you might get really nice time (considering six 5 mW diodes) - just rough estimate without doing math.