Heatsinking issue? Let me know

[frogmaster]

Long time lurker first time poster - anyway, I have a ~4v 50mw green laser with a driver from China hooked up to a 9v battery, and the power is stepped down with an adjustable buck converter to prevent the 9v from overpowering the circuit and heating. Anyway the laser runs great for a few seconds, but after time goes by and about ~30s constant use it dims then suddenly drops dramatically.

Obviously this is a heatsinking issue - I've tested multiple batteries, including a CR123a battery just in case. Weird though because it's in a brass case and inside an aluminium mounting holder I bought for it. Does my laser just suck? More are on the way, they're cheap and easy to get even in the pandemic we're having, so it could just be a crap example right?

Thanks for any help and go easy I'm new haha.

 

[Cyparagon]

Your power decisions are erratic and uninformed, as is your diagnosis. Give it a standard (charged!) 18650 cell as power like a normal person and report back.

 

[LaserMicroscope]

Cyparagon is, unsurprisingly, right. Stepping down 9V with a buck converter is a really unusual (for good reason) setup, that is almost certainly what’s failing you. hook it up to an appropriate li-ion for that driver and see if you continue to have problems, rather than stepping down a chemical battery

 

[Snecho]

I didn’t see you mention any kind of driver, so I’ll assume you don’t have one? If that’s the case...get a driver! Then hook it up to an appropriate li-ion for that driver and see if you continue to have problems.

anyway, I have a ~4v 50mw green laser with a driver from China hooked up to a 9v battery

 

[LaserMicroscope]

Derp, I really need to stop posting from my phone, can’t read as I type! Edited the original, thanks for the fact check Snecho!

 

[frogmaster]

Your power decisions are erratic and uninformed, as is your diagnosis. Give it a standard (charged!) 18650 cell as power like a normal person and report back.

Okay thanks for the response, albeit patronising, it's useful. Have a good day.

 

[frogmaster]

Cyparagon is, unsurprisingly, right. Stepping down 9V with a buck converter is a really unusual (for good reason) setup, that is almost certainly what’s failing you. hook it up to an appropriate li-ion for that driver and see if you continue to have problems, rather than stepping down a chemical battery

Yeah I understood chemical consumer batteries have their issues for a very long time, my main reason for using this is basically because I wanted something that can be easily and cheaply recharged on the fly with cells that are very common, as opposed to using more of a specialist 'mail order' type of battery. What do you recommend to help here? Frustratingly even the cr123a is prone to causing the same issue. Nine volt chemical batteries are a super common part that's often left lying around, which is why I've made that choice, I wonder if there is a way to do this and make it work...

 

[Cyparagon]

I wanted something that can be easily and cheaply recharged on the fly with cells that are very common

1) Why? 18650s are far more energy dense than a 9V alkaline and are easily rechargeable.

2) if you meant "hot-swapping" new cells in for instant use, why have you not used 2x (or perhaps 3x, depending on driver specifications) AAs? 2xAAs has nearly twice the energy of a 9V and are about 1/4 the price.

 

[LaserMicroscope]

Yeah I understood chemical consumer batteries have their issues for a very long time, my main reason for using this is basically because I wanted something that can be easily and cheaply recharged on the fly with cells that are very common, as opposed to using more of a specialist 'mail order' type of battery. What do you recommend to help here? Frustratingly even the cr123a is prone to causing the same issue. Nine volt chemical batteries are a super common part that's often left lying around, which is why I've made that choice, I wonder if there is a way to do this and make it work...

18650 batteries are a great, and fairly standardized choice. Although a lot of stores are closed right now, they're quite readily available if you have a vape store near you, as most vapes run on those batteries (though the mail order ones may be better for lasers, since you're able to order "button top" style batteries rather than the "flat top" style available for vapes). These stores also sell chargers, though they tend to be relatively expensive. However, I've seen very inexpensive eBay and Amazon listings for 18650 charging cradles that should work for testing purposes. It's a few dollars investment in the battery and charger but it isn't too much, plus the battery will be much more reliable and useful than chemical batteries. I'm not a circuitry expert, but the nature of chemical batteries would make a project using them much more difficult and likely expensive than investing in a lithium ion that will work for you out of the box.

 

[frogmaster]

18650 batteries are a great, and fairly standardized choice. Although a lot of stores are closed right now, they're quite readily available if you have a vape store near you, as most vapes run on those batteries (though the mail order ones may be better for lasers, since you're able to order "button top" style batteries rather than the "flat top" style available for vapes). These stores also sell chargers, though they tend to be relatively expensive. However, I've seen very inexpensive eBay and Amazon listings for 18650 charging cradles that should work for testing purposes. It's a few dollars investment in the battery and charger but it isn't too much, plus the battery will be much more reliable and useful than chemical batteries. I'm not a circuitry expert, but the nature of chemical batteries would make a project using them much more difficult and likely expensive than investing in a lithium ion that will work for you out of the box.

Yeah I have lithium cr123's and the holders for them and might get some rechargeable ones but still, this diode is doing the same thing with those which is odd. I haven't seen them do this with other diodes either so I think I might have just had some bad luck.