Victron - Only Charge from Solar

Does anyone know if it is possible to set a Victron inverter such that it only ever charges from solar power?

At the moment, I can “semi” do it by setting scheduled charging, but if I want to use a high “stop on SoC” (like 90%) it would also charge from the grid. I’d like to start using the battery after it is full enough, so not sure if I can hack together such a solution with the settings at my disposal.

The reason I’m asking is due to the proposed CoCT regulations, limiting the amount of current you may pull from the grid to charge your batteries. That seems to be the toughest one to get around without limiting inverter power.

If I am able to enable an “only charge from solar” setting, behind a “password”, then I can manually limit the inverter power and charge from the grid if ever I feel like the batteries need a full charge after days of bad weather. All other times, I would be able to be ensure that there’s no chance I could ever charge from the grid and exceed their limit.

While I do feel the charging limit is a silly rule to implement just on those with generating capacity, because the real demand would come from those with only backup system, I guess one needs to operate within the confines given to you.

Maybe I’m missing something but is the default with ESS not to only use solar to recharge the batts?

Only time I use Eskom is to top-up, like Keep Charged, when SOC is below the level I would prefer for scheduled LS events.

And the way I use Scheduled Charging is to set a a very low SOC like 35% to not discharge batteries. So it will only use Eskom IF SOC is <35% … if I ever get there.

Yes, you are correct that ESS only charge from solar, but I remember that there’s a condition that would necessitate charge from the grid.

So, while unlikely, for legal reasons I guess it need to be “impossible”?

I know you can limit or even disable your AC Charger entirely in VEConfig if you wanted to.

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Which condition, can you recall?

I would hazard and guess that to meet the max amps for battery charging, that it must be limited on not only the inverter, but also under DVCC.

And that it is AC amps, not DC amps.

That is if ones BMS does not already limit the max DC amps for charging.

I THINK, and I stand to be corrected, that for example, on a 60amp main house breaker, I get the impression that one must limit battery charging to 3.5kw AC.

Ah good! I’ll go have a look, that would solve the problem.

Isn’t it when the battery drops more than 5% below minimum SoC?

Yes, so 25% of your maximum current is the limit. So 15*230 = 3,450W.

Not that I’m aware of no. Unless you manually override it.

Let’s look at this, correct me where I miss something.
If one charge at say 56v 70amps - 5kva MPII max DC amps with lithium batts - that is 3920w DC.

Google says: You get to AC watts by multiplying the PTC DC wattage by the inverter efficiency.

3920w x 0.96 (5kva MPII efficiency) = 3763.2 AC watts.

So on a 5kva MPII one needs to shave off 263.2w AC off the max charging ability of the inverter.
That is IF you can charge your bank at 56v 70amps DC.

BUT … if one has 2, 3 or 6 x 5kva MPII connected in parallel, yeah, that does become a wee bit of an issue on a 60amp main breaker.

Sorry, made a typo, 5% below min SoC. Maybe I assumed it would happen after reading the ESS doc.

Your MPII 5kVA can invert 5kW from the AC side, and you might have roughly 4.5kW then on the DC side. Every trip from AC to DC (or DC to AC) loses roughly 10%.

Grid tied MPII is limited at max 4kw AC continues, temp derating dependant.

And if one limits the 5kva to the requried 3.5kw AC max, that solves the problem quite nicely, no?
For limitting the inverter to 3.5kw will also limit the DC side to max 3.5kw AC charging … I think?

So IF I am right, then there is no problem if one limits the inverter to 3.5kw AC as per regulations.

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You could limit it, but you lose a lot of capacity. The MPII is max 5kW. The temp derating is normal to any electronic item.

I’d prefer to have a solution that only limits the AC charger, but not the DC to AC inverting capacity.

The Multi II will charge from the grid if your SOC is too low much below the min SOC. It looks to be a value between 5-10%.

So say you have min SOC=50% and there was a power cut and your SOC went down to 35%. As soon as the grid is back up the Multi will charge the batteries to 50% (or perhaps 45%) using the grid if your solar is not producing enough current.

@jykenmynie what you can do is to set the max charge current for the Multi (Ve.Config or VictronConnect).
Each MPPT also has it’s own max charge current which can be different from the Multi, so you can set a low limit for the Multi and much higher for the MPPT(s).

What I am not certain about is if using ESS influence the charge current up if it is different like the above.

What about setting the AC Input current limit, then you won’t take more than X from the Grid ever… depending on your situation that could either be good or bad :slight_smile: Think we discussed this elsewhere, not sure if anything has changed regarding the proposed regulations.

*Edit see Louisvdw beat me to it.

Haha no this would definitely not work, because my my instantaneous demand on the inverter’s circuits could definitely exceed 3.5kW.

There is a setting “Max charge power” that was used before DVCC became the normal.

Something I’ve often wanted is a limit overall charge to X, AC charge to Y. For example, some days I want to say “Keep batteries charged… but don’t use AC to do it”.

Why don’t we have it yet? Cause there needs to be enough demand for it to outweigh the additional load in support that arises because people a) don’t know what it is for, b) configure it incorrectly, c) don’t bother to read the manual before asking questions…


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Hang on…

Why not just configure the maximum charge current in VE.Configure. Done…


Now THAT is something one would really appreciate a lot!
Option 1: Keep Charged using AC
Option 2: Keep Charged using Solar Only
No need for manual …

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Well this is effectively exactly what I really want! Many days, when I see it is cloudy or so, I would like to use this option. Don’t want to run the batteries down to min SoC just to warm my geyser. So now I enable one of my scheduled charging settings, but it isn’t perfect.

This is what I’ll look into when I’m done with work. @PJJ suggested it also.

Have they actually worded it for “battery charging”?

They use something like “maximum battery charging current limit”.

Great! That helps clear up a few things then