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Is 4.2v 18650 beter, than 3.7 (for green one)

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xappys

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Hi there, so i want to know will 4.2v 18650 battery make the laser stronger, and how about diode lifetime, laser heat.
P.S. Laser - chinese one
 





4.2v is the max charge on 3.7v batteries. Your talking about the same batteries here.
 
L-Ion batteries are said to be 3.7V by the manufacturers, but they charge to just about 4.20V... Fully charging a batery will make it stronger as long as the laser is made to handle 4.2V :)
 
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So...... Yes.... Lol don't be so quick to dispute when you're asking the question. :p
 
Lithium technology does not allow for a 4.2V cell to my knowledge. This is a mistranslation/miscommunication/lie... just like the "4200mAh" bullshit.

NKO29 said:
Fully charging a batery will make it stronger
Click to expand...

This is wrong. Laser drivers operate on constant current. Increasing the voltage will not change the current, because the current is held constant.
 
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Cyparagon said:
Lithium technology does not allow for a 4.2V cell to my knowledge. This is a mistranslation/miscommunication/lie... just like the "4200mAh" bullshit.

This is wrong. Laser drivers operate on constant current. Increasing the voltage will not change the current, because the current is held constant.
Click to expand...

Actually you are wrong i'm afraid. I had some L-Ion cells charging over night, every single one charged to almost exactly 4.20v (tested on a DMM). And fully charging batteries will allow them to output more current in general, plus the more voltage the better for green lasers. When you get close to the lasing threshold voltage, there can be considerable drops in power which may vary from laser to laser.
 
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If I had one read 4.6 Volts, I think I would take it out in the back
yard away from the house!!! These cells can be bad news if over
charged or discharged.
HMike
 
NKO29 said:
Actually you are wrong i'm afraid. I had some L-Ion cells charging over night, every single one charged to almost exactly 4.20v (tested on a DMM). And fully charging batteries will allow them to output more current in general, plus the more voltage the better for green lasers. When you get close to the lasing threshold voltage, there can be considerable drops in power which may vary from laser to laser.
Click to expand...

Only if the laser is drawing enough where the internal resistance of the battery is a problem, and in the pointer hobby, that's not gonna happen.

The idea of a constant current driver (which is used on pretty much all lasers) is that their current draw will not change, no matter what the voltage. In fact, if the laser uses a buck driver, you'll notice the current from the battery _decreasing_ with higher voltage.
 
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NKO29 said:
When you get close to the lasing threshold voltage, there can be considerable drops in power
Click to expand...

Which is why the threshold is NOT at 4V by design. If you want to split hairs, I'll give you this much: If the laser isn't a piece of shit, battery charge level will not matter. Is that a fair statement?
 
Yes, but if there is NOT ENOUGH voltage then you will drop power no matter how much current can be supplied. This is quite easily seen when diodes are tested... The higher the current, the more voltage needed. Having the extra voltage as long as the driver can handle it isn't a bad thing. And i can't agree that battery charge doesnt matter even on GOOD lasers. There is a reason why you NEED to recharge batteries once in a while.
However i do see how plainly saying "Fully charging a battery will make it stronger" may not be correct :whistle:
 
YOu both are right. It just depends on how you are looking at it. By using linear or buck drivers the charging level and the battery voltage will not matter that much but for boost drivers it will. A linear driver will drain for a long time the same amount of current till the minimum voltage for diode and driver is reached. The same for a buck driver. But a boost driver also converts voltage into current and there it of course matters.

Hoever all those cheap chinese pointers are using linear drivers, so this will drain the same amount of current till the battery gets discharged.
 
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NKO29 said:
if there is NOT ENOUGH voltage then you will drop power
Click to expand...

And that is exactly why drivers are ideally designed to work within the charge range of the supply. If the driver only works down to 4V, the designer is at fault - it is not a general rule.

Let's take green for example since this was OP's question. The forward voltage of the pump diode is Something like 1.9V. Even the cheapest green ebay pens have a driver that has a minimum dropout of 0.6V or so. This puts the operating range of even the cheapest of green drivers at 2.5V+. Anything above 2.5V (i.e. EVERYTHING for a lithium cell) will not increase the power of the laser.
 
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