Solar Panel Voltage Boost Troubleshooting

[davidsuzuki256]

Hello,

I Have built a 50w solar panel that gives an output of ~ 9.2v @ 5-6 amps during a good day. This is not enough to charge a 12v battery. To get around this, I am trying to use a DC-DC boost converter (specifications are below) and it is set to give an output voltage of 13.5v. The only problem I have is that the output voltage drops out after 10 seconds if the output voltage is set beyond 12.5v. Input voltage becomes the same as output voltage thereafter.

Here are the specifications of the Dc-Dc boost converter:

Specification:
Size:(LxWxH) 70 x 39 x 32 mm
Wide Input Voltage Range: DC 6 ~ 35V
Output Voltage: DC 1 ~ 35V
Conversion Efficiency: 90%
Maximum Output Current : 5A
Maximum Input Current : 7A
Operating Frequency : 120KHz

What am I doing wrong?

David

 

[berkeman]

Hello,

I Have built a 50w solar panel that gives an output of ~ 9.2v @ 5-6 amps during a good day. This is not enough to charge a 12v battery. To get around this, I am trying to use a DC-DC boost converter (specifications are below) and it is set to give an output voltage of 13.5v. The only problem I have is that the output voltage drops out after 10 seconds if the output voltage is set beyond 12.5v. Input voltage becomes the same as output voltage thereafter.

Here are the specifications of the Dc-Dc boost converter:

Specification:
Size:(LxWxH) 70 x 39 x 32 mm
Wide Input Voltage Range: DC 6 ~ 35V
Output Voltage: DC 1 ~ 35V
Conversion Efficiency: 90%
Maximum Output Current : 5A
Maximum Input Current : 7A
Operating Frequency : 120KHz

What am I doing wrong?

David

Welcome to the PF.

That's a pretty small input-output voltage differential for a simple boost DC-DC converter. You might need to use a SEPIC topology converter instead. Which boost converter chip are you using and with what component values?

 

[berkeman]

Or, wait. You are using a canned commercial DC-DC converter module? Can you link to the datasheet?

 

[davidsuzuki256]

Thanks for the response.

I am using this dc-dc boost converter: link.

I do not really care much about the output amp value. Only the output voltage has to be at least 13.5 for the boost converter to charge the battery. Unfortunately it doesn't last long and it will return to the open circuit voltage of the solar panel after 10-15 seconds. The booster also makes some ticking noises before the voltage drops to solar panel voltage.

 

[Tom.G]

Your description of shutting down is almost always due to overload, current or thermal overload in this case. That particular model seems to be discontinued. Check this site to see if another model will fill your needs. Link. And pay attention to the warning about its usage!

 

[tech99]

Hello,

Battery may be drawing more than the rated current. Check with an ammeter. Also what type of battery - I assume lead acid.

 

[anorlunda]

What is the voltage of the 12V battery before connecting it to the solar panel?

 

[jim hardy]

As TomG and anorlunda have hinted it might be a problem of application.

What controls output current to the battery ? How much do you measure going to the battery ? Did you notice this caution in the directions at link you posted ?

 

[jim hardy]

I Have built a 50w solar panel that gives an output of ~ 9.2v @ 5-6 amps during a good day...
...
What am I doing wrong?

Without some numbers we can only guess what is wrong.
Hook it up again and take some measurements.

1. What is voltage from solar panel just before the stepup converter shuts down?
2. What is current into the battery at that time ?

Can you try this experiment - rewire your panels in series not parallel so they make 18 volts instead of 9 ?
Then connect them straight to battery without the converter and see how much current flows when sun is bright. Don't leave them connected very long lest you overcharge the battery.
That gives us a data point on solar panel's current capability.

Then insert your converter between the solar panel and battery and let it step 18 volts down to 13.5
In bright sun it should operate as step down and in weak sun it should act as step up,
and if i have read that datasheet correctly it'll auto-select whichever it needs.
With a little bit of luck the inherent current limiting nature of your solar panel will cure the trouble.
If not you might have to employ a current limiter.

old jim