Multi RS Solar needs Invertor load to charge battery

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Rain And Storm asked Jan 16, '24

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) ♦ commented · Jan 17 at 09:56 AM

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 Thiemo van Engelen (Victron Energy staff) ♦ commented · Jan 17 at 09:24 PM

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) ♦ Rain And Storm commented · Jan 18 at 08:12 AM

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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Rain And Storm Thiemo van Engelen (Victron Energy staff) ♦ commented · Jan 19 at 01:13 AM

Multi_RS_Smart48_6000_100.vcsf.zip

Here it is, my unit's latest settings.

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multi-rs-smart48-6000-100vcsf.zip (7.5 KiB)

Thiemo van Engelen (Victron Energy staff) ♦ Rain And Storm commented · Jan 22 at 08:33 AM

Hi @Rain And Storm

Thank you for the settings file. We will look into the issue. Just be sure, the settings are completely the same as when the problem occurs with the solar not working, except that On/Off->Mode is set to On instead of "Charger Only"? Or did you also change other settings?

Kind regards,

Thiemo van Engelen

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Rain And Storm Thiemo van Engelen (Victron Energy staff) ♦ commented · Jan 22 at 02:47 PM

I confirm, the settings are the same, what I currently have set on my Multi RS.

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Thiemo van Engelen (Victron Energy staff) ♦ Rain And Storm commented · Jan 22 at 10:16 AM

Hi @Rain And Storm

We are still investigating, although we were unable to reproduce the issue in a quick test. We did however find some unusual settings:

ESS mode is set to External Control. For an off-grid setup, it is advised to change this to "Keep batteries charged"
The Charge Detect voltage is set to 58.4V. This prevents the inverter from turning on after it turned off a few times on under-voltage. This should be set lower than the absorption voltage.

Do you also have the Epoch batteries somehow connected to the MultiRS (except via the battery + and -)?

Kind regards,

Thiemo van Engelen

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Rain And Storm Thiemo van Engelen (Victron Energy staff) ♦ commented · Jan 22 at 02:54 PM

Just changed it to "Keep batteries charged", thank you. I played around with that ESS thing so much... it doesn't seem to affect the problem that the MPPT stops charging after there's no load on the inverter. I'm also sorry to say, I still don't know what ESS stands for, even after going through the manual.

I just set the charge detect to 56V, but I played with that setting a lot, it never seems to affect anything in my setup. I assume it's an auto-shutdown mechanism to prevent usage of empty batteries for 230V?

I only have + and - that go from Multi RS to my batteries, but these things have RJ-45 ports on them, I just have no idea what they're for, I perhaps could connect them to the Multi RS, if they're supposed to talk to each other to exchange information about the charge level and other things. I know Epoch's upcoming batteries have some kind of magical integration with Victron, but not sure about mine.

Thank you for all the tips and looking into this issue.

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Answer 1 · 2024-01-16T18:43:44Z

Alex Pescaru answered · Jan 16 at 06:43 PM

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 commented · Jan 16 at 06:48 PM

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 Rain And Storm commented · Jan 16 at 06:53 PM

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 Alex Pescaru commented · Jan 16 at 07:01 PM

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 Rain And Storm commented · Jan 16 at 07:07 PM

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 Rain And Storm commented · Jan 16 at 06:57 PM

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 Alex Pescaru commented · Jan 16 at 07:13 PM

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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Answer 2 · 2024-01-18T03:16:21Z

Paul B answered · Jan 18 at 03:16 AM

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 commented · Jan 19 at 01:09 AM

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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