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Rain And Storm avatar image
Rain And Storm asked

Multi RS Solar needs Invertor load to charge battery

For some reason, my Multi RS Solar connected to a 1KW PV array doesn't charge my LiFePo4 battery bank (Epoch Batteries), unless it's also outputting at least 30W via 230VAC (Inverter). I have no AC in from the grid (it's a yacht), so solar is my only way of charging the batteries and powering the AC circuit.

If I set the mode into "Charger only", it just won't pull anything from the PV array, and hence not charge the batteries. But once I set it to "On", it immediately discovers there's like 400W of solar coming from the panels, and starts both charging the battery bank, and inverting for whatever I have plugged in (usually Starlink is enough, it tends to draw above 45W non-stop).

I'm currently talking to Epoch Batteries, but no idea if it's a conflict that's happening between their charge mosfet and Victron's battery charger, or something else.

Any hints would be highly appreciated.

Multi RS
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Thiemo van Engelen (Victron Energy staff) avatar image Thiemo van Engelen (Victron Energy staff) ♦ commented ·

Hi @Rain And Storm

Do you also have a GX device (CCGX, Cerbo GX, Raspberry Pi vith Venus, etcetera) connected?

If not, what are the other devices in the system, for example BMS, other chargers, etcetera?

Can you post some screen shots of the settings of the Multi RS?

Kind regards,

Thiemo van Engelen

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Rain And Storm avatar image Rain And Storm Thiemo van Engelen (Victron Energy staff) ♦ commented ·

Hi @Thiemo van Engelen (Victron Energy staff)


No, nothing else is connected to my Multi RS or the batteries at the moment. Here's what it looks like on a sunny day in January, without the 230VAC load, and then with my Starlink plugged in. If I unplug the load or set the mode to "Charger only", the 400W drops down to 0–17W a few minutes later, then keeps jumping up and down, but never getting up to 400W again. Then when I put even a 25W load on the inverter, the MPPT starts pumping 400W+ into the battery again. If I take snapshots of settings from my mobile app, it'll be like 10 images, and there's really nothing that I'd call unusual. I can still do it if you think it might help, but perhaps exporting the settings file and attaching it here would be more useful?


I suspect it's the problem with the firmware, I've tried all possible settings and tweaks I could do by now. It also might be the way the charge mosfet works in the batteries I have, that they conflict with Victron's load detection algorithm, leading to a catch-22 type of situation, where the charger is looking for something to charge, and the battery is not asking to get charged because it doesn't see any power coming from the charger, a limbo of sorts.


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Thiemo van Engelen (Victron Energy staff) avatar image Thiemo van Engelen (Victron Energy staff) ♦ Rain And Storm commented ·

Hi @Rain And Storm

Exporting the settings file is indeed also a possibility and it would help. I think you need to zip the file as this forum does not accept .vcfs files.

Regards,

Thiemo van Engelen

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2 Answers
Alex Pescaru avatar image
Alex Pescaru answered ·

From Multi RS manual reading...


Charger Only

Charger only mode turns off the Inverter providing AC voltage to the AC output.
The charger will charge the batteries from the AC input in this mode


So, on the yacht, without AC input, no charging... On the other hand...


Inverter Only
Inverter only mode disconnects the AC input from the grid by opening the AC input relay.
The solar charger is still active in this mode.


I believe the ON mode is best for you, because will charge the batteries from solar and also provide AC output when needed, also from solar and batteries when no solar is available.

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Rain And Storm avatar image Rain And Storm commented ·
Interesting. But then it starts charging batteries from solar once there's even a small load on the Inverter, while still no AC input... Shouldn't there be a mode for charging from solar, if the inverter is off or has no load on it?
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Alex Pescaru avatar image Alex Pescaru Rain And Storm commented ·

Try Pass Through.

This mode closes the AC input relay and passes through AC voltage from the AC input to the AC output while the inverter/charger remains off. - in your case no power with be passed through.
The solar charger remains active.


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Rain And Storm avatar image Rain And Storm Alex Pescaru commented ·
Thank you for the advice. I set it to Passthrough, disconnected Starlink, it kept charging my battery at around 60W for something like 10 minutes, then gave up on charging, as usual. I see similar behavior when I start with On, and then set it to Charger only — it'll continue charging for a couple of minutes, and then forget about solar again. But if I plug in Starlink or any other load, it suddenly starts charging my batteries from solar again.
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Alex Pescaru avatar image Alex Pescaru Rain And Storm commented ·

Do you have the last firmware programmed?

That firmware also improves MPP trackers for maximum solar harvest.

https://community.victronenergy.com/questions/255304/rs-shade-performance-testing-v116-beta-04.html


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Alex Pescaru avatar image Alex Pescaru Rain And Storm commented ·

It's strange that in Charger only mode you have power to the AC Output for you to use...

Maybe it's a secondary effect because some electronics blocks are shared inside Multi RS between inverter/solar/dc bus/dc conversion.


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Rain And Storm avatar image Rain And Storm Alex Pescaru commented ·

Yeah, it's a real pickle. I've been trying to figure this one out for months now. My assumption has always been that MPPT chargers just try to capture as much solar as possible, and give it to the battery no matter what.

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Paul B avatar image
Paul B answered ·

I would also check that you have the latest firmware installed for this unit. i have attached the changelog for the diferant fw versions in case this helps - Multi RS Inverter RS and MPPT RS firmware changelog.pdf


multi-rs-inverter-rs-and-mppt-rs-firmware-changelo.pdf (206.7 KiB)
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Rain And Storm avatar image Rain And Storm commented ·
Thank you for the PDF! I have v1.15, the latest. The iOS app is great at updating it, really neat.
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