Solar charge controller connection sequence

[daleyocum]

The manual for some of my solar gear, like the Renogy panels, say to connect the charge controller to the battery before connecting the panels. Is this just for the initial setup? I was hoping to have the solar charge controller (Victron 100/30) always connected to the array ( with a disconnect for service) and then have the charge controller downstream from the master disconnect for the system’s batteries. Is the charge controller going to get mad about not having a battery to charge?

The system is using Lithiums which don’t need be constantly on charge while in storage.

I could connect the charge controller right onto the battery bank so the master disconnect doesn’t effect it.

[alano]

Your solar charger should be connected directly across your batteries. While in storage your charger should detect when they are fully charged and not supply current to the batteries. The disconnect between the panels and the charger is recommended and useful if you're doing maintenance on the charger for any reason.

[wulfraat]

Doesn’t really matter which you connect first to the controller - panels or batt.

Best practice is to place a mechanical disconnect switch to/from panels and to/from batts.

If you live in cold climate with lithium’s, also best practice to place a low temperature automatic disconnect such as the victron BatteryProtect so as not to charge your batteries below 2C.

[daleyocum]

Originally Posted by alano

Your solar charger should be connected directly across your batteries. While in storage your charger should detect when they are fully charged and not supply current to the batteries. The disconnect between the panels and the charger is recommended and useful if you're doing maintenance on the charger for any reason.

The downside to conecting directly across the battery is that the Victron battery monitor (which is currently downstream from the master cutoff switch) won’t be able to incorporate the solar power into it’s calculations.

[uncle_bob]

Hi

On the Victron the beast recognizes if you have a 24V or a 12V battery when it is first connected. Apparently this process can get confused if you hook up the panels first. Since there are ways to switch around the battery voltage, that is not a massive issue if you catch it quickly. If you don't catch it, your battery gets a bit of a boost ( if it's a 12V battery and the charger thinks it's a 24V).

On some lithium batteries, the internal BMS will do cool things like disconnect it from charge ( and from discharge) at cold temperatures. What you get depends a lot on which battery you buy. How much you trust this or that feature .... hmmm .....

Bob

[daleyocum]

Originally Posted by wulfraat

Doesn’t really matter which you connect first to the controller - panels or batt.

Best practice is to place a mechanical disconnect switch to/from panels and to/from batts.

If you live in cold climate with lithium’s, also best practice to place a low temperature automatic disconnect such as the victron BatteryProtect so as not to charge your batteries below 2C.

Agreed. These are the Battleborn batteries that has the battery management and temperature sensor built in. None the less it seems like I’d want to turn off the solar when storing for a long period of time just to be safe.

[gklott]

Originally Posted by daleyocum

The manual for some of my solar gear, like the Renogy panels, say to connect the charge controller to the battery before connecting the panels. Is this just for the initial setup? I was hoping to have the solar charge controller (Victron 100/30) always connected to the array ( with a disconnect for service) and then have the charge controller downstream from the master disconnect for the system’s batteries. Is the charge controller going to get mad about not having a battery to charge?
The system is using Lithiums which don’t need be constantly on charge while in storage.
I could connect the charge controller right onto the battery bank so the master disconnect doesn’t effect it.

Most solar charge controllers should have battery connected to the controller before connecting the PV power source. That powers the charger's micro-controller. The Victron 100/30 manual section 3.4 specifies the connection sequence. The manual safety section says "Connections must always be made in the sequence described..."

To be NEC compliant, and to follow Victron instructions, your PV source wiring should likely be the following:
- Panel(s) to string fuse
- string fuse to combiner box (string fuses may be part of the combiner box)
- combiner box to 2-pole PV disconnect switch (PV + and -)
- PV disconnect switch to 2-pole over current protection device (OCPD - fuse or circuit breaker). The OCPD may be rated for use as a disconnect.
- PV OCPD to ground fault protection device (GFPD)
- GFPD to Victron charge controller

Your 2-pole PV disconnect should be accessible from outside your trailer for first responder use.

Your PV charging wiring should likely be:
- Victron charge controller + to OCPD
- OCPD to battery + (terminal or bus)
- Charge controller - to battery - (terminal or bus)

Your battery management system and the Victron charger (properly configured) should prevent overcharging and handle low temperature, high temperature, high voltage, low voltage, etc.

The trailer's "master" disconnect is for turning off DC branch circuits. You must not back feed charge through that disconnect switch - as this could lead to having a voltage present on the branch circuits when you think they are disconnected. Victron 100/30 manual says "WARNING: DC (PV) INPUT NOT ISOLATED FROM BATTERY CIRCUIT."

73/gus

[uncle_bob]

Hi

I have yet to see any RV come from the factory with factory solar an externally mounted solar disconnect switch .....( or any solar disconnect switch for that matter ....). Not saying it is a bad idea at all. Just that it is not commonly done that way.

Bob

[gklott]

Originally Posted by uncle_bob

I have yet to see any RV come from the factory with factory solar an externally mounted solar disconnect switch .....( or any solar disconnect switch for that matter ....). Not saying it is a bad idea at all. Just that it is not commonly done that way. Bob

Agree, just like many installations lack string fuses, UL-listed combiner box, DC ground fault protection devices, etc.

ANSI_RVIA Standard for Low Voltage Systems 2014 Edition does not address PV systems. PV is not even listed in Chapter 2 as a potential power source. Have not received my 2018 edition, which is 16 pages long just like the 2014 edition.

A RV PV system is a stand-alone system, and the corresponding NEC 690.1(b) diagram shows the PV DC disconnect location.
690.13 says "Means shall be provided to disconnect the PV system from all wiring systems,...
690.13(A) says the "PV disconnecting means shall be installed at a readily accessible location."
690.13(F) says "The PV system disconnect means shall simultaneously disconnect the PV system conductors of the circuit from all conductors of other wiring systems." Note plural conductor'S' - meaning a 2-pole switch like the Blue Sea 6010.

Unfortunately, many factories and installers figure a "readily accessible location" is buried under a bench or bed inside. NEC 100 says "capable of being reached quickly for operation, renewal, or inspections without requiring those to whom ready access is requisite to use tools (other than keys), to climb over or under, remove obstacles, or to resort to portable ladders, and so forth."

Our fixed PV disconnect is just inside the refrigerator vent door on the street side, with labeling outside identifying "NOTICE: ROOF PV SYSTEM DISCONNECT INSIDE" We also have a separate portable PV system capability, and that disconnect switch is in trailer tongue box.

Even more rarely than a PV disconnect switch do you find companies and installers properly marking and labeling PV systems per NEC 690, OSHA, and NHTSA.

Today, NEC Article 690 represents best industry, engineering, and life-safety practice. Hopefully the RV industry will learn from expanding PV system use.

73/gus
Dr. Gus Lott, P.E.

[pdavitt]

Gus,


Totally agree. But, since the Travel Trailer side of the RV industry is not regulated, don't see any changes coming in the near future.

The image below was included in another post. I particularly like the inclusion of the AC/DC electrical equipment and wiring in an enclosed space with the water pump and plumbing. Not to mention the rat's nest of wires. I guess ignorance is bliss.


Pat

[slackerchef]

Hello, great question and thread.

My understanding is that you must hook the controller to the battery 1st, before hooking it up to your panels (i'm using 130watts of panels connected to a Victron 100/20, and a StarkPower 125A LiFePO4 battery). i installed a fuse between the panels and controller just in case i have to disconnect the battery, so not to disrupt the recommended connection procedure. you can also just throw a blanket over your panels before disconnecting your battery (if you need to for whatever reason), so the controller will not get any current from the panels while not connected to a battery.

just my 2...

best wishes!

[daleyocum]

Since I want the battery monitor to know what’s going on with the solar array and I don’t want it running when the main disconnect is turned off I’m considering wiring things in the following order

Battery bank
400 amp fuse
Battery monitor shunt (it’s power operating power coming after the main disconnect)
Solar charge controller
Main disconnnect switch
Everything else

I’d have string fuses for the charge controller and battery monitor power.

This means the Victron solar charge controller is always running and charging/monitoring the battery. The Battleborn batteries won’t charge below freezing but still I was hoping to not have them charging at all in long term storage. Not seeing an easy way to do that though and keep the Solar Charge Cntroller happy (power before PV.) I’ll have switches for the PV array, of course, but I don’t want to risk someone who doesn’t know all the detail turning things on in the wrong order.

Thoughts?

[gklott]

Originally Posted by pdavitt

Gus,Totally agree. But, since the Travel Trailer side of the RV industry is not regulated, don't see any changes coming in the near future.

Buyer beware - especially when you pay top-$$$ for an Airstream.

When we make changes, that's our chance to make improvements. That's why daleyocum's question is important - so they can get it right.

Originally Posted by pdavitt

The image below was included in another post. I particularly like the inclusion of the AC/DC electrical equipment and wiring in an enclosed space with the water pump and plumbing. Not to mention the rat's nest of wires. I guess ignorance is bliss.

I view this image with abhorrence. It's indicative of sloppy design, terrible workmanship, absent quality assurance process, and manufacturer prostitution for the dollar.

From our experience (i.e., sample of one), all Airstream flooring is installed over rivet shanks, metal cuttings and filings, dirt, and pieces of paper.

With images like this one, we can hope that all potential Airstream owners will enter the purchase process with their eyes wide open.

That's a value of AirForums - Buyer Aware!

73/gus

[daleyocum]

Originally Posted by daleyocum

Since I want the battery monitor to know what’s going on with the solar array and I don’t want it running when the main disconnect is turned off I’m considering wiring things in the following order

Battery bank
400 amp fuse
Battery monitor shunt (it’s power operating power coming after the main disconnect)
Solar charge controller
Main disconnnect switch
Everything else

I’d have string fuses for the charge controller and battery monitor power.

This means the Victron solar charge controller is always running and charging/monitoring the battery. The Battleborn batteries won’t charge below freezing but still I was hoping to not have them charging at all in long term storage. Not seeing an easy way to do that though and keep the Solar Charge Cntroller happy (power before PV.) I’ll have switches for the PV array, of course, but I don’t want to risk someone who doesn’t know all the detail turning things on in the wrong order.

Thoughts?

One change. I’ll have to put the main disconnect on the positive side so turning it off turns off the battery monitor. The charge controller positive would connect straight to the battery before the disconnect (through a string fuse.).