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SWSherrill · 02-15-2025, 10:53 AM

I recently upgraded from 2017 FC 23FB with solar panels/AGM batteries to 2024 FC 27FBT with solar panels/Lithium batteries. I live at 7300 ft with pretty chilly winters. I removed my lithium batteries and are storing them in my mechanical room, with occasional top off with battery tender. I do not keep the battery tender hooked up the entire time, about once a month top them off.

My question though is what to do with the solar panels as I cannot disconnect them easily and noticed during the daytime, they like to re-energize by battery disconnect switch. I can push the switch to store mode and next day it is pretty bright green circle. At night it will store again as the solar panels are literally controlling it. To me, this is not right. I cannot put my batteries in store mode with solar panels taking control every day. Is this how it is supposed to be wired? My 2017 airstream did not have this issue. So new to me. Will this prematurely where the battery disconnect switch out as it cycles daily? Is the battery disconnect switch not programmed correctly? I believe this switches are for the coaches and not like the old switches we had say for my 2017 AS. It appear THOR is literally taking over these days and application is not for trailers.

PaulBristol · 02-15-2025, 11:26 AM

If you have removed the lithium batteries from the FC, do not regularly top them off. Generally they should be left alone for a long period.

There is a voltage at which they should be recharged. Get the instructions for the make and model of batteries. Follow the storage instructions.

Since the batteries are not in the FC, the solar controller can not charge the batteries. The batteries can not be discharged by parasitic loads.

I don't know why the 12 volt disconnect continues to turn itself "ON". It may be the default action when power goes from "OFF" overnight to "ON" when the solar controller powers up in the sunlight.

What ever the cause, I don't know why it would be a problem. The batteries need protection from flat out discharge. Other things should be fine.

The solar controller may have an "OFF" setting. Check the manual.

Al and Missy · 02-15-2025, 12:28 PM

Best practices for solar install has a disconnect switch between the panels and charge controller for safety. If you have one, turn it off. If not, consider adding one.

kb0zke · 02-15-2025, 02:47 PM

Al and Missy are right on. I don't know why manufacturers don't put the disconnect in, but they don't. Now that it is starting to warm up I will be adding one to our trailer.

BGClassic · 02-15-2025, 02:58 PM

Concur. I added a solar disconnect (DPDT) box on the PV wires from the panels. I also added a Blue Sea DC disconnect so I no longer have to remove batteries in the winter.

Nate of Explorist Life channel on YouTube has a good video on the solar disconnect. If I had to guess, the solar charge controller voltage potential is enough to illuminate that LED in the battery disconnect switch. A quick visual of the solar controller LEDs will reveal that.

Wazbro · 02-15-2025, 05:03 PM

"Is this how it is supposed to be wired?"
No, absolutely not, there should be a shutoff before the solar controller.
Unfortunately it is wired the way Airstream normally wires it.

It has been reported as a "normal" way for it to act.
It is a really bad thing as the solar controller may not regulate the voltage anywhere near well enough to not damage the electronics in your trailer without the batteries.

JeffKim · 02-15-2025, 05:11 PM

A little more detail. The solar controller is wired to the positive bus bar and energizes the DC side regardless of whether the batteries are installed. It's just how it is. When I took out our batteries to install lithium, Mrs. JeffKim was watching TV and I was puzzled for a bit until I realized the solar was powering it.

Like others, I installed a solar disconnect switch so I don't get surprises. However, if you swap out the standard Victron Blue controller for a Victron Smart (easy to do), you can turn off the charger via Bluetooth. With the Blue there might be a menu item in the solar display to turn it off, I've never looked.

Other than being annoying I don't think having the solar controller in operation hurts anything. It might try charging at 14.4V or so but that shouldn't hurt anything.

os1r1s · 02-15-2025, 07:06 PM

You can turn the Solar BlueSmart charger off through a CerboGX connection.

Quote:

Originally Posted by JeffKim

A little more detail. The solar controller is wired to the positive bus bar and energizes the DC side regardless of whether the batteries are installed. It's just how it is. When I took out our batteries to install lithium, Mrs. JeffKim was watching TV and I was puzzled for a bit until I realized the solar was powering it.

Like others, I installed a solar disconnect switch so I don't get surprises. However, if you swap out the standard Victron Blue controller for a Victron Smart (easy to do), you can turn off the charger via Bluetooth. With the Blue there might be a menu item in the solar display to turn it off, I've never looked.

Other than being annoying I don't think having the solar controller in operation hurts anything. It might try charging at 14.4V or so but that shouldn't hurt anything.

**richard5933** · 02-15-2025, 10:04 PM

It's generally considered a bad idea to have the solar panels providing power to the solar charge controller if there are no batteries connected. Put a manual disconnect switch on the positive line feeding the solar charge converter. This is a simple operation and using a Blue Sea battery switch of the proper voltage/amp capacity should do the trick.

PaulBristol · 02-16-2025, 06:38 AM

I recommend you read and follow manufacturer's instructions for batteries as well as solar controllers. They are not all the same.

Victron provides manuals for all its equipment. If you need help understanding, Victron provides on-line help. Victron dealers are also helpful.

It is unlikely the Victron solar controller will switch to Bulk mode without batteries installed. It is possible. The controller requires high current flow to do that.

Even if it does, all modern 12 volt RV appliances are designed to work with 14.4 volts DC.

Again not all brands and models are the same. They are electronic devices and do what ever they are designed to do. Read the instructions.

SWSherrill · 02-16-2025, 09:32 AM

100% Agreed. Will do this when weather warms up.

Mollysdad · 02-16-2025, 09:43 AM

Quote:

Originally Posted by BGClassic

Concur. I added a solar disconnect (DPDT) box on the PV wires from the panels.

I don't have roof solar but I'm putting together a standalone system with the components (not batteries) in a case. I followed Nate pretty closely because being a solar rookie, I didn't want anything burning up.
Yes, the disconnect needs to be a DPDT D.C. disconnect. I used a DC Circuit breaker with a high enough rating there's no danger of it tripping. A DC breaker is different than a AC breaker in the it has a device to snuff out arcing internally as the contacts move. I used this:
60 amp. I decided not to use the connectors and instead run my in's and out's directly to the terminals with ferules. This is between the panels and controller. The + output of the controller goes through a Blue Seas switch so I can turn off the batteries from the controller.
Here's my amateur diagram.