Shore power Battery charging with Solar

[Dkoelfgen]

Hello,
Putting 400 wts. of Solar with Victron MPPT 100/50 Charge controller on my 2011 27' Flying Cloud. My question is; What do I do with the existing MagneTec 7300 Converter? Can I leave it connected? What happens when we connect to shore power? Can I leave the Solar/ Victron 100/50 connected to the battery bank (Flooded batteries for now)? Thinking they might not interact too well.
Appreciate any help
DK

[BayouBiker]

You leave the 7300 connected they are compatible. Both sense battery voltage / condition and adjust accordingly. The Victron has adjustable setpoints so if you understand the characteristics of your batteries and the behavior of the 7300 you can tune it. I won't explain it here because it really does not make all that much difference. If you change out your wet cells to AGM or lithium then some adjustments perhaps are warranted.

When you connect to shore power, they sorta compete with each other and contribute to varying degrees to the charging process, they adjust current to maintain the charge voltage patterns programmed into the units and when the voltage setpoints are reached they switch to maintain or float modes. So all is good even with the default settings.

You can leave them connected. They will do fine. Not perfect, but fine. If you want them to interact perfectly, you can go to the online battery schools, learn about your particular configuration and adjust the Victron. Honestly, I wouldn't bother if I were you. Now if you get other style batteries, sure you should make some adjustments.

[AirMiles]

You can leave your 7300 connected and use it when you need to charge your batteries with shore power or a generator.

I turn off the circuit breaker that powers my Airstream's shore power converter unless I want it to charge with shore power or a generator. I very seldom turned on that breaker with 400W on my 25' Airstream. On my 25' FBQ, the converter and the bedroom 120V outlets were on the same circuit. On my 27', the converter is on its own circuit - YAY! I haven't needed to charge with anything but solar in over 100 days of camping in the past year. I still carry my generator so I can use the microwave or A/C, but my batteries stay fully charged with solar.

[BayouBiker]

I guess the question I would ask is why do you turn off your converter? Is is based on a feeling you have? Intuition? or fact? Are you certain your batteries are best served only being charged solar?

[AirMiles]

Originally Posted by BayouBiker

I guess the question I would ask is why do you turn off your converter? Is is based on a feeling you have? Intuition? or fact? Are you certain your batteries are best served only being charged solar?

My Victron solar controller's charging profile is completely custom programmable with voltage and temperature compensation. The stock controller on my 2017 Airstream only charged at a continuous 13.6V and my 2018's stock controller only charged at 13.6V or floated at 13.2V, both without voltage or temperature compensation. I upgraded both stock controllers to a true multi-stage PD4655 that charges at 14.4V, 13.6V and 13.2V, which still does not perfectly match the charging parameters of my batteries. My Victron solar controller's charging profile has been programmed to match my battery manufacturer's recommended charging parameters.

[BayouBiker]

That is an excellent answer.

[Hermes]

The simple solution for us was to switch to "Store" mode (Use/Store switch) when plugged into shore power, in which case the converter doesn't compete with the solar charge controller (which is always "On"). This solution may vary from one trailer model/year to the next.

If and when we need the converter to charge the battery bank (rarely), then we switch to "Use" mode and we closely monitor the battery charge level and switch back to"Store" mode when we reach 85-90% full and let the solar controller finish the job. Our batteries are in top shape (and they stay in the trailer all year round).

Our MPPT charge controller adjusts the charge according to the battery temperature; our stock converter is not that sophisticated but is does a good job in supplying 12V to the trailer when we are plugged into AC power, so there was no need to replace it (we put the $ in the solar system which is working great).

[Dkoelfgen]

"The simple solution for us was to switch to "Store" mode (Use/Store switch) when plugged into shore power, in which case the converter doesn't compete with the solar charge controller (which is always "On"). This solution may vary from one trailer model/year to the next.

If and when we need the converter to charge the battery bank (rarely), then we switch to "Use" mode and we closely monitor the battery charge level and switch back to"Store" mode when we reach 85-90% full and let the solar controller finish the job. Our batteries are in top shape (and they stay in the trailer all year round).

Our MPPT charge controller adjusts the charge according to the battery temperature; our stock converter is not that sophisticated but is does a good job in supplying 12V to the trailer when we are plugged into AC power, so there was no need to replace it (we put the $ in the solar system which is working great)".

I like this method. That way you know for sure if your solar system is keeping up to your DC power consumption (assuming your not running an Inverter).
Did you install the "Use/Store switch" or did your AS come with it?

Thanks everyone for all the great replies!
DK

[Hermes]

Originally Posted by Dkoelfgen

Did you install the "Use/Store switch" or did your AS come with it?
DK

The Use/Store switch is a standard feature on Airstreams (usually situated by the door). The Use/Store toggle switch activates a solenoid switch (a mechanical switch which makes contact by moving a metal connector using a magnetic field). There are two 5 amp fuses on either side of the solenoid (for the magnet) which need to be operational for the switch to do its job.

When not connected to shore power, putting it in Store mode, cuts most of the current draw from the batteries (except for the propane detector, the subwoofer, the radio's channel memory feed, the tongue jack and the electric brakes-- which can eventually slowly drain the batteries when in storage for a long period).

But when connected to shore power all appliances requiring 12V to operate (fridge, furnace, hot water heater, lighting, etc.) are operational via the converter even when in Store mode -- except that the converter doesn't charge the batteries (but as I mentioned in my previous post, this is not the case in all model/years of Airstreams; you need to check your manual or contact your dealer).

We use Use mode pretty well only when we are towing (to keep the fridge running on propane, it needs a bit of 12V power) or when boondocking.

[Hermes]

Originally Posted by Dkoelfgen

I like this method. That way you know for sure if your solar system is keeping up to your DC power consumption (assuming your not running an Inverter).

DK

The MPPT controller (Blue Sky 3024iL, 40A, 12V) comes with a monitor that I installed, out of the way, in the galley cabinet by our L couch. It displays all the information you would need to monitor the battery bank and is used to program all the controller's charge parameters according to the battery manufacturer's specs.

Other brands, such as Victron have bluetooth capability and you can do this on your phone. I liked the concept of a permanent install in the trailer.

So it's a matter of keeping an eye on the monitor, but after a while you pretty well know how much you are drawing on average. We do run the inverter but never have felt the need to leave it on for long periods, and with 500W of panels and 470ah of storage, we have never been in a "crisis" situation (or needed to connect the Honda generator-- except to run one of our A/Cs which has an EasyStart controller).