Pulsing

[AndrewB]

Hi there, new to the forum. I have an issue with a solar panel. I've tried google searching but cannot find a topic with the same issue. I have a 130 watt solar panel. Whenever it starts to produce more than 8 watts the amperage starts to pulse back and forth from 0 to whatever the output amps is. When the amperage output is below 8 it has a nice steady output. When the amperage is pulsing the voltage is staying stable. Anyone have an idea as to what could cause this? And is it possible to fix?

Thanks
Andrew

[sensij]

What is regulating the current being produced? If you are using a charge controller to a battery, what is the battery voltage when the pulsing starts? It is possible that the higher output current is driving the battery voltage over whatever threshold the controller uses to determine end of charge.

[littleharbor]

What are you powering with the panel? It sounds like you are hooked directly to a larger load than the panel can power and it is causing the output to collapse.

[AndrewB]

Its hooked to a 20 A CC then to 2 deep cycle batteries. I should have mentioned I have been running this setup for a couple years now. This pulsing thing just started a couple months ago. It worked fine with no pulsing before. Last week I got a new charge controller thinking it may have been it causing the issue, but same results.

[AndrewB]

Open voltage is 17.5. Charge level of battery doesn't seem to have any effect on the pulsing. Seems to be only when the output of panel is over 8 A

[sensij]

Open voltage is 17.5. Charge level of battery doesn't seem to have any effect on the pulsing. Seems to be only when the output of panel is over 8 A

How are you determining the charge level of the battery? Due to its internal resistance, the higher the current you apply, the higher the voltage you will read instantaneously, even if the actual charge level is lower. As batteries age, they become more susceptible to this.

Also, what specific charge controller are you using?

It is *possible* there is a crack in a junction or trace in the solar panel that only opens up in certain thermal conditions (for example, passing high current), but I would try changing out the battery first.

[AndrewB]

How are you determining the charge level of the battery? Due to its internal resistance, the higher the current you apply, the higher the voltage you will read instantaneously, even if the actual charge level is lower. As batteries age, they become more susceptible to this.

Also, what specific charge controller are you using?

It is *possible* there is a crack in a junction or trace in the solar panel that only opens up in certain thermal conditions (for example, passing high current), but I would try changing out the battery first.

I'm determining the charge level of the battery from what what is displayed on the CC.
I don't remember which brand charge controller it is off the top of my head and its at my camp which I wont be back to until Friday. However I've replaced the cc and still getting same results.

A bad battery could cause this even though its on the other side of the cc?

[sensij]

A bad battery could cause this even though its on the other side of the cc?

Yes. The CC determines what to do based on what it senses from the battery. If the battery voltage is spiking when hit with high current (as old batteries tend to do), the CC would react by disconnecting the solar panel (which drops its output to zero). With on/off and PWM type controllers, the panels are basically connected straight through to the battery. With mppt type controllers, it is more complicated. The pulsing you are describing would be typical for a cheap controller... more expensive controllers tend to do a better job of smoothing out the on/off oscillations, but can still be subject to the same effect.

[AndrewB]

Yes. The CC determines what to do based on what it senses from the battery. If the battery voltage is spiking when hit with high current (as old batteries tend to do), the CC would react by disconnecting the solar panel (which drops its output to zero). With on/off and PWM type controllers, the panels are basically connected straight through to the battery. With mppt type controllers, it is more complicated. The pulsing you are describing would be typical for a cheap controller... more expensive controllers tend to do a better job of smoothing out the on/off oscillations, but can still be subject to the same effect.

Ok. I did try 1 battery at a time, so perhaps both are bad. They are only 6 month old magnacharge batteries but I guess still possible. And yes its a cheaper PWM controller. I will have to try it with a different battery and see. Thanks for input

[sensij]

Ok. I did try 1 battery at a time, so perhaps both are bad. They are only 6 month old magnacharge batteries but I guess still possible. And yes its a cheaper PWM controller. I will have to try it with a different battery and see. Thanks for input

One battery at a time would actually make the effect worse (assuming they were in parallel), since all the current is hitting a single battery instead of being divided between the two.

[AndrewB]

One battery at a time would actually make the effect worse (assuming they were in parallel), since all the current is hitting a single battery instead of being divided between the two.

Ok, good to know.
Having left this all hooked up, is there any risk of more damage being caused?

[sensij]

Ok, good to know.
Having left this all hooked up, is there any risk of more damage being caused?

Well, the longer the battery goes without a good charge, the more damage it takes, but the panels and charge controller should be fine. Getting a good charge might require a different type of controller that could nurse it to a healthier state, but that might not be worth the effort if it is far enough gone.