Solar Panel Charge Waveform

[DarkSkySeeker]

I wanted to see what my solar panel was doing when charging my batteries so I borrowed a single board oscilloscope from a friend and took this video. This explains why my analog ammeter doesn't show any current flow.

Youtube

[time2roll]

Assuming you have decent wire size the battery voltage and panel voltage will be the same except for the voltage drop in the wire. If the panel voltage is 17.0 and the battery voltage is 14.0 you need to pull new wire.

[MrWizard]

time2roll wrote:

Lwiddis wrote:
When would a solar controller not be regulating power?

During bulk phase

That would depend on the output voltage of the panel,
Bulk voltage is higher, but is not equal to panel voltage, which is usually above 17v even fully loaded, if in good sun

[time2roll]

MrWizard wrote:
And reading will be wrong if set to VAC

Best to look at the optional settings in the link above.

[MrWizard]

20ms pulses
50 ? Pulses per second on a DC circuit
Meter can't respond to that on a DC setting
And reading will be wrong if set to VAC

[time2roll]

Put a 10 amp load on the battery and see if it reads anything.
That meter with an internal shunt should work just fine with PWM voltage control.

[DarkSkySeeker]

time2roll wrote:

• The waveform is likely showing VOLTAGE not CURRENT. You need an "amp clamp" or shunt to read current
• Meters, true analog or DMM are just not "fast enough" to read the pulses

It is voltage, yes.
The analog meter looks like this:
Amazon

[time2roll]

Maybe we need a picture of the meter and how it is connected to get no reading.

[theoldwizard1]

time2roll wrote:

DarkSkySeeker wrote:
I wanted to see what my solar panel was doing when charging my batteries so I borrowed a single board oscilloscope from a friend and took this video. This explains why my analog ammeter doesn't show any current flow.

Youtube

What scale are you using? Could be just a few milliamps.

I am not convinced that wave form would disable your analog meter.

• The waveform is likely showing VOLTAGE not CURRENT. You need an "amp clamp" or shunt to read current
• Meters, true analog or DMM are just not "fast enough" to read the pulses
• Pulsing a load (the battery in this case) is a common method used in modern (>40 years) electronics for controlling power. Think of filling a bucket with water from faucet. Bursts of water control how fast the bucket is filled. Very small burst means it take longer.

[time2roll]

DarkSkySeeker wrote:
I wanted to see what my solar panel was doing when charging my batteries so I borrowed a single board oscilloscope from a friend and took this video. This explains why my analog ammeter doesn't show any current flow.

Youtube

What scale are you using? Could be just a few milliamps.

I am not convinced that wave form would disable your analog meter.

[time2roll]

Lwiddis wrote:
When would a solar controller not be regulating power?

During bulk phase

[DrewE]

DarkSkySeeker wrote:

Son of Norway wrote:
OK, I have noticed the same thing with my analog meter. Can you explain to me how the waveform on the oscilloscope shows why the analog meter won't work? (I have three kids who are engineers, so obviously the apples sometimes DO fall far from the tree.)

When the charge is applied in 10-20ms pulses, an analog meter can not respond - at least mine - which is a mechanical needle in a housing. By the time the needle wants to rise as the voltage rises and current flows, the voltage drops and the current stops. The needle can't respond.

It should be responding to the average current; it's effectively a mechanical low-pass filter or integrator. My conclusion would be that the net current is quite low, basically zero, which stands to reason if the controller is having to limit the power from the panel.

[BFL13]

Lwiddis wrote:
When would a solar controller not be regulating power?

The idea is to not let the voltage at the battery go above the high set point. Once the voltage (at the controller) gets that high, the controller starts controlling. PWM is one way to do the controlling.

[Lwiddis]

When would a solar controller not be regulating power?

[red31]

What about at times when the controllers is not regulating power?