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thomm225 · 05-11-2016, 05:21

Quote:

Originally Posted by Bleemus

Not sure if I am following correctly but it is normal to get those voltages from solar panels. My two Kyocera 140 watt panels in parallel will put out about 18 volts and my MPPT controller will convert the extra volts to more amps unlike a PWM which shuts down when voltage hits the set level. Do you think you have a fault seeing 22volts?

I did some more checks on the panel and batteries for clarification.

With the system hooked up for 24 hours (the day was sunny) the panel side read 18.5 volts while the battery side of the controller read 14.4 volts. This indicates the batteries are nearly fully charged (low current flow)

Now when I disconnect the panel from the load, in this case the batteries, the "floating" unloaded panel read 21.5 volts at 4pm. (we sometimes called open circuits in digital electronics floating when there was an open)

Checking the batteries the next morning, they read 12.7.

Now when I plug the panel back in, the panel read 13.1 volts and the batteries 12.8 (due to current flow while the batteries are charging) If you continue to monitor these voltages for the next few hours, you will see the panel side voltage increase after the voltage reaches 14.4 or so on the battery side as the batteries start to near full charge

I read the label on the back of my 100 Watt solar panel yesterday......the Voc Rating is the Voltage Open Circuit. Mine is rated at 22.56 Volts. I've seen 22 volts with the panel unplugged from the load mid day during the summer.

As far as the term floating, I remembered that 5 volts floating read about 2.2 volts are so on a meter or O'scope. (this was/is very helpful information when troubleshooting digital TTL Circuits because you knew you had no current flow in that area) It just took a while for the memory to come back. We'd use the term floating and open circuit almost synonymously while troubleshooting in the 80's and 90's

As I said before, there is very little circuit troubleshooting done these days unless we cannot buy the replacement item. We do still at times troubleshoot our old CRT Monitors with their late 80's early 90's circuitry. Some flight simulators still use these for their displays bouncing the image of a mirror etc

Digital electronics

Main article: Three-state logic
In digital circuits, a high impedance (also known as hi-Z, tri-stated, or floating) output is not being driven to any defined logic level by the output circuit. The signal is neither driven to a logical high nor low level; this third condition leads to the description "tri-stated". Such a signal can be seen as an open circuit (or "floating" wire)

transmitterdan · 05-11-2016, 10:06

A solar panel is never in a hi-z or tristate condition. The correct nomenclature for a disconnected panel is open circuit voltage.

thomm225 · 06-11-2016, 09:48

Quote:

Originally Posted by transmitterdan

A solar panel is never in a hi-z or tristate condition. The correct nomenclature for a disconnected panel is open circuit voltage.

I was explaining why a person that was a long time technician in the age of digital electronics might refer to an unplugged/unloaded(disconnected) solar panel as floating....

When I unplug the panel from the batteries you will read somewhere between 19-22.56 volts through the controller all the way up to the alligator clips for the battery because the panel, controller, and wiring, etc are all floating....... not connected to anything........ not even ground.

It's like when you are troubleshooting a chassis that isn't grounded. You can get all kinds of crazy large signals on your O'Scope if the chassis is floating.......until you connect the probe ground to the floating chassis