Laser Driver Max Voltage Input

[Arc]

I have a red laser with lm317 driver and would like to try and run it from a solar panel. It is not a very big panel only rated for 4W but on a sunny day it puts out up to 21V. I normally only use this laser with 8.4V max. That is why I didn't want to try using it yet before seeking a bit of advice. My concerns are
1) Will the diode be harmed or stressed in any way?
2) Will the driver be harmed or stressed in any way?

And,

3) I know that this driver and diode combination need a minimum of 6V to run and below that laser performance starts dropping. Now with Li-Ion cells the voltage under load is less than the voltage under no load. My question is as follows. Is the 6V minimum requirement under load or under no load condition. For example when the cells have gone from 8.4V full charge down to somewhere in the range of 6-7V then I was under the impression that the cells still have a bit of charge left. But I realised that under load they will be getting down below 6V so I wondered whether this will start to impact laser performance since the voltage is sagging below the 6V during operation. Or does just the no load voltage need to be above 6V?

 

[Cyparagon]

21V 4W means the panel cannot output more than about 200mA. You wouldn't need a driver to begin with, since the panel limits its own current. The extra voltage would be lost as heat in the panel. You could keep the driver in, and the extra voltage would still be lost as heat in the panel because the driver would load the panel too much.

Electrics of the panel aside, the LM317 can operate up to a little over 30V, provided you have adequate heat sinking.

Use a lower voltage, higher power panel.

 

[Arc]

Cool thanks for the advice. I tried running it with a driver and it worked great. It could only power 1 diode at a time though. Are you very sure the solar panel can safely power the diode without a driver? If so I will try it and hopefully this is more efficient than using a driver allowing the panel to power 2 diodes at a time. In doing this should I wire up the diodes in series or parallel?

 

[The Lightning Stalker]

Put them in series. That way the current
through them will be the same. I wouldn't
connect the diodes directly to the panel
until you are absolutely sure it won't
overdrive them just in case it's an
overachiever. What diodes are you using?