532nm laser fades after (about) one second

[saffi]

Hi there,

Bought this incredible SDlaser 302 5000mw green laser off some Chinese site. It even has a 8000mw sticker on it Anyway, sinc it was not very expensive, came with a 18650 Ultrafire battery and charger, and it's my first "more powerful" laser I thought I just take the gamble. It shipped quite fast (16 days with Chinese New Year in between) and upon arrival I was quite happy with it (and also happy customs didn't intercept). Since I have no reference I guess the "real power" is somewhere between 5-10 mw. Nice laser to start with no?

I played around with it for a while (since we have a lot of air traffic here I'm very reluctant to point it towards the sky) and was amazed by the clear beam and nice round dot without any flaws. I must have used it for about ten minutes tops over a period of 4 hours and then it faded. I wanted to charge the battery but the charges gives a green light almost immediately.

I'm confused as to whether the pointer broke down or I have battery problems. Here's all the info I have:

Laser dims after a second (or two). When I try more times, it dims faster.
Laser wasn't dropped/shaken etc. there's no "rattling sound" inside (and huh, you didn't shake it ,.. I did a bit to find out there's no .....
Beam is perfectly bright and well focused the one second it burns.

My thoughts were: Battery!!

So I focused on that:

Battery charger goes green moments after I put the battery in. I measured voltage and the battery has a 3.96 volt reading. Charger puts out 4.18 volts. I just measured the battery after a couple of tries in the laser and I noticed the voltage dropped to 3,65.

I then measured the power consumption (and my son was happy he was allowed to push the button). The first tries it starts at around 0.26 A/h and drops very quickly to around 0.06 or lower. Each subsequent try it starts lower (0.10, 0,09 etc.) and drops fast.

That's in line with trying out the laser... It fades faster and faster, until it doesn't work anymore. When I give it a rest it burns again for a very short time...

I obviously need another battery to test but I'd like to hear your opinion, battery or laser?

Regards, Saffi

 

[Speedy78]

From all this it sounds like you have a crap battery. It shouldn't show are fully charged green light that fast. Try replacing the battery with a more quality one and see if the problem is resolved.

 

[Zeebit]

I must have used it for about ten minutes tops over a period of 4 hours and then it faded.

You used it for 10 minutes straight? You could have fried the pump diode or crystals inside.

Have you tried a new battery?

 

[RedDart]

This often happens to eBay 532nm's, they are bright for a split second then go dimmer, it's usually a battery or circuit problem... Or you simply overdid it with your cycles

 

[saffi]

You used it for 10 minutes straight? You could have fried the pump diode or crystals inside.

Have you tried a new battery?

Not ten minutes straight. Over the course of some hours max 20 seconds at a time.

I think it must be the battery. The laser dims faster the more you try and when you leave it for an while it lasts longer again. Also I noticed that battery voltage drops below 3,6 volts after a few tries...

I'll try and get a good battery somewhere and try again...

 

[Cube777]

It could be a high internal resistance of the battery, this will cause a huge lag in voltage as soon as there is a load and this could mean that the voltage is to low for the circuitry to work (It will be okay for a very short period of time and then lag and cause the dimming). This can be caused by an old battery, just a crap battery or one that has been exposed to heat for prolonged periods of time. I would also recommend a new, better battery, if you have some money to spend you can buy some of LarryDFW's batteries here on the forum which are great batteries.

 

[Moistenator]

You used it for 10 minutes straight? You could have fried the pump diode or crystals inside.

Have you tried a new battery?

Had he have fried the diode, He wouldn't get any peak at startup at all.

 

[mojo_1234]

have some cheap laser pointer laying around with same symptom.

It's just caused by bad quality of the small (glued) crystal set doing the job to convert the 808nm IR into 532nm. Most green laser pointers/modules are overdriven (-> pod mod) and that's just too much for the small crystals. So it's a non reversible thermal issue.

These "dimmed" lasers often do some crazy mode hopping. If you "move" the laser dot quite fast along a wall you might see the different modes hopping/oscillating... and this is not an issue with driver or battery...

 

[Cube777]

@OP Before you buy new batteries test its internal resistance by following this post: HERE. We can then test mojo_1234's theory.

 

[BShanahan14rulz]

If battery charges quickly, doesn't indicate it is broken, and isn't capable of powering laser, might be a fake battery. Here's an example of a possible reason why the large cell isn't capable of powering laser: http://laserpointerforums.com/f67/fake-ultrafire-18650-s-72833.html

 

[saffi]

@OP Before you buy new batteries test its internal resistance by following this post: HERE. We can then test mojo_1234's theory.

A high internal resistance would also explain why the charger goes green straight away right? I have to find a 4/5 Ohm power resistor somewhere..

I don't think it's a misaligned crystal. The spot perfect the few seconds it lasts. But hey, I'm newbee :yh:

 

[Cube777]

Remember, the battery is actually fully charged, it just sags when you attach a load. So your trying to charge an already full battery, that might be why it charges so fast.

 

[phenol]

Don't you have an adjustable bench power supply to test the laser with?

 

[saffi]

Don't you have an adjustable bench power supply to test the laser with?

No, although I should have some model train power supply somewhere but the power output is quite low (and isn't it AC power?).

 

[Benm]

You need properly rectified, smooth, dc current to operate a laser off.

If you want to test things, you should probably borrow a lab power supply, configure that to 3.6 volts and powre the laser with it.

If it doesn't dim on that, the problem is in the battery. If it still does, the problem is in the laser itself, probably a thermal issue. The problem with these 532 greens is that their performance is extremely sensitive to temperature, and in some cases heating up the laser during just a few seconds of operation can degrade output power severly. On others, it is the opposite and it takes some time for the laser to warm up before producing full power.

 

[mojo_1234]

missed the important part :beer:

if current drops like mentioned - should be no problem with optics...

this sounds more like a problemo with battery or driver

sorry

...

I then measured the power consumption (and my son was happy he was allowed to push the button). The first tries it starts at around 0.26 A/h and drops very quickly to around 0.06 or lower. Each subsequent try it starts lower (0.10, 0,09 etc.) and drops fast.

...

Regards, Saffi