Blinking lights, noise from speakers, 12V fluctuates

[MrScott1]

Ran into an electrical system oscillation issue and wanted to share what was happening. We have a 2022 Forest River Adrenaline toy hauler with 300W solar panel, however this applies to any system with both shore power and solar (multiple independent power sources).

Symptoms:
Symptoms vary, here is an example of the issue:

• Ceiling lights blink out
• Sound from the built-in speakers at the blink
• Fan-Tastic Vent cuts out for a moment at the blink
• LiFePO4 battery voltage 'blinks' out
• Sometimes, turning on more of a load stops the oscillat

Workarounds:
While there is shore power, disable and/or reduce the solar charge current setting way down (our controller and/or the app for it doesn't seem to want to leave the controller disabled). Or, cover the solar panel.
Turn on more loads.

Problem is, sometimes the extension cord feeding the trailer gets dislodged during storage...

What I Think Is Happening:
Basically, different control systems are 'fighting' each other, resulting in a system level oscillation.
BTW I am an electrical engineer. Don't have much equipment with me on our trip, just an inexpensive multimeter, so no graphs etc.

1. The LiFePO4 battery has short circuit protection and charge limiting; it will switch charging sharply on and off, causing a varying load on the 12V bus
2. The power converter has both an overvoltage protection "crowbar circuit" and short-circuit protection; other equipment may have a crowbar as well
3. A "crowbar" circuit protects against power supply regulation failure putting excessive voltage on the bus; better to blow a fuse than fry expensive equipment!
4. The shore power converter supplies power to the 12V bus
5. The solar controller adds power to the 12V bus as well -- with a different voltage limit, or perhaps voltage spikes when the load varies
6. When the 12V bus gets to an excessive voltage, the "crowbar" circuit triggers and shorts it out to ground
7. Short circuit protection kicks in all around, saving the equipment (repetitive shorts are hard on it, though) and the wiring from being melted by the battery power
8. The 12V bus voltage drops, no more overvoltage: the crowbar resets and everything recovers
9. The 12V bus voltage rises again to overvoltage and the cycle repeats

Unless and until you have a single controller that prevents these independent (and independently designed) systems from fighting each other, try turning the solar charger off while on shore power. The challenge is remembering to turn it back on again, every time, and noticing when the TT loses power during storage. Perhaps there is an 'inhibit' terminal on some make of panel controller, that could sense shore power?

[Larry-NC]

Originally Posted by MrScott1

Ran into an electrical system oscillation issue and wanted to share what was happening. We have a 2022 Forest River Adrenaline toy hauler with 300W solar panel, however this applies to any system with both shore power and solar (multiple independent power sources).

Symptoms:
Symptoms vary, here is an example of the issue:

• Ceiling lights blink out
• Sound from the built-in speakers at the blink
• Fan-Tastic Vent cuts out for a moment at the blink
• LiFePO4 battery voltage 'blinks' out
• Sometimes, turning on more of a load stops the oscillat

Workarounds:
While there is shore power, disable and/or reduce the solar charge current setting way down (our controller and/or the app for it doesn't seem to want to leave the controller disabled). Or, cover the solar panel.
Turn on more loads.

What I Think Is Happening:
Basically, different control systems are 'fighting' each other, resulting in a system level oscillation.
BTW I am an electrical engineer.

1. The LiFePO4 battery has short circuit protection and charge limiting; it will switch charging sharply on and off, causing a varying load on the 12V bus
2. The power converter has both an overvoltage protection "crowbar circuit" and short-circuit protection; other equipment may have a crowbar as well
3. A "crowbar" circuit protects against power supply regulation failure putting excessive voltage on the bus; better to blow a fuse than fry expensive equipment!
4. The shore power converter supplies power to the 12V bus
5. The solar controller adds power to the 12V bus as well -- with a different voltage limit, or perhaps voltage spikes when the load varies
6. When the 12V bus gets to an excessive voltage, the "crowbar" circuit triggers and shorts it out to ground
7. Short circuit protection kicks in all around, saving the equipment (repetitive shorts are hard on it, though) and the wiring from being melted by the battery power
8. The 12V bus voltage drops, no more overvoltage: the crowbar resets and everything recovers
9. The 12V bus voltage rises again to overvoltage and the cycle repeats

Unless and until you have a single controller that prevents these independently designed systems from fighting each other, try turning the solar charger off while on shore power. The challenge is remembering to turn it back on again, every time. Perhaps there is an 'inhibit' terminal on some make of panel controller?

Hmm...Thought about putting your 'scope on it and capturing one of these events?

I bought this clever device a year ago, figuring that I could run it from my laptop and write a macro with a circular buffer to capture and freeze on events like this.

[MrScott1]

Thought about it, yes. Have a scope with me, no.

BTW having once blown up a $300..400 motherboard after bumping a USB clip against the wrong pin, I would hesitate to connect a USB scope to a laptop or PC.

[TacomaJoe]

What brand of LiFePO4 battery? I've seen posts of LiTime having issues when fully charged, the BMS shuts off and won't turn on until a load is detected.

[MrScott1]

An interesting idea. Although, the power converter alone supplies enough power to charge the battery as well as carrying the existing loads; why would the voltage drop? That would require a load step exceeding the ability of the power converter to keep up. Perhaps the refrigerator motor kicking on? Plus the solar system having a pulsating output?

Either way, temporarily disabling the second power source made the issue stop.

[TacomaJoe]

Is your solar controller PWM or MPPT? Having multiple charging sources shouldn't be an issue, there are a whole bunch of us with converters and solar on the buss. My normal is a converter and MPPT solar but at times I add another solar controller and if I'm in generator mode, I can toss on another 70A charger. All of them work together.

You shouldn't be that close to crowbar levels. I would review all the charging parameters and dial down some voltages if need be. My solar floats at 14.2V, if I change for 14.3V one of my batteries will have a cell overvolt. 14.2 is the sweet spot and I don't have it on all the time.

Here is a link to the Ampere Time battery that has the BMS cut the load for a moment (at about 11:00 in the video).

https://www.youtube.com/watch?v=MzGN9d0Sb9E

They changed names to Li time but still have a BMS shut off "feature".