Why Solar Panel Voltage Drops When Connected The Radio?

Hello,

I own a Brunton Solaris 6 solar panel with the power rating of 12v 6W and short circuit voltage of 19v. We were living together just fine until I got a Yaesu Vx-8dr Radio. It charges on 12v 0.5A AC adapter. I decided to charge it with my PV but when I connect the panel voltage drops under 12v to 9v and Radio doesn't charge showing a External DC tag which indicates the lower voltage. The only time I get a charge with this setup is when the panel oriented to the sun perfectly in high solar conditions which is too perfect to sustain. I tried to wire it with 80 Ohm resister to limit the current but didn't help. How can I stabilize the voltage and also carry the solution in my backpack? Thank you for your attention and help.

Comments

[steveastrouk]

Your problem is that the charging requires more power than your little panel can supply.

Its working perfectly, and in accordance with the numbers you;'ve given. A solar panel is rated at full sun, normal to the sun's direction "too perfect to maintain" is a great description.

Unfortunately, a 6W system needs 6W from the panel.

Incidently, you can't HAVE a short circuit VOLTAGE of 19V.

"limiting current" will only make matters much, much worse.

Steve

[LongLongBow]

Thank you for your quick answer.

There is one thing left bothering me.

This panel generates some power even it is slightly lower then the device needs. I want to take that in use somehow. Charge speed isn't a matter.

12v voltage is the only thing that radio needs to get the charge. If I'm right about it current is a matter of charge time.

If there is a way to stop radio to pull that much current, the voltage will rise right? If current limiting with a resistor does harm then good, any other solution left? I can go to the end since this panel is the only reasonably light one that I can carry in to the mountains.

May be should I store that power somehow and then charge the radio? But direct charging will be a lighter solution for my backpack.

[steveastrouk]

I've just reviewed the manual for the radio, the charging spec is definitely 12V 1 amp ! Can you check the charger rating ?

Steve

[LongLongBow]

The original wall adapter came with the radio was 12V 0.5A. Now I'm using a 12v 1A adapter. both are working fine.

I had a spare solar panel which is rated 10W. I tried it with my Brunton Solaris 6w in the same light conditions right now.

10w panel managed to charge it showing 16v
Solaris 6 couldn't and showed 10v

I hope these will help.

[steveastrouk]

Have you any way to measure the real charging current ?

Steve

[LongLongBow]

I mesured it. ammeter started from 0.45A and stabilized at 0.35A

[steveastrouk]

Sorry, you need more panel :-(

Make one of your own ?

Steve

[LongLongBow]

Thank you for your kind efford. Now I know that it wont be possible with this panel. Thank you.

[steveastrouk]

Please don't forget to mark this as the Best Answer, for other's reference !

Steve

[lemonie]

Get a second (identical) panel, wire in parallel.

L

[LongLongBow]

Thank you for your answer. Since I have limited space in my packpack and the cost of this king of CIGS solar panels are some 100$ I need to stick with the one I have right now.