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Johnny Lee avatar image
Johnny Lee asked

ESS - Keep Batteries Charged in United States?

Hello,

I am in the US using Multiplus-II + CerboGX in a RV setup with batteries, solar, and shore power. I would like to use shore power to power loads, charge the battery. When I have solar, I would like to use solar first and reduce my shore power load, but NOT feed any excess power to the grid.

This aligns with "Connect to mains, no Feedback" in Self-consumption Hub-1. But the materials say that is deprecated in favor of ESS. This aligns with "Keep Batteries charged" in ESS. However, I can't install ESS without selecting a grid code... and there is no Grid code in for the USA.

Solar priority seems like a common configuration with other solar/inverter systems, how do I do this with Victron?

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2 Answers
JohnC avatar image
JohnC answered ·

Hi @Johnny Lee

Victron strongly advise against using ESS in a mobile situation. And even then, playing with gridcodes etc could lead you into a situation you can't get out of, like 'unpublished' passwords and other stuff.

You don't give enough info on what you have and want. If you really mean 'keep batteries charged', then just set the solar charger settings 0.1V (or even less) higher than the shore charger. That's with a fixed Float/Storage V, but you may want a daily Absorb cycle. Then it gets more complex, with even Temp Comp getting involved with pb batteries.

DVCC is something you should probably be using anyway, and there's a little in there about priorities, which may/not apply to you. https://www.victronenergy.com/media/pg/Cerbo_GX/en/dvcc---distributed-voltage-and-current-control.html

And if what you actually want is to find a little battery space for really maximizing the solar harvest, then that can be done too with Assistants, shutting down Shore power based on the parameters you choose.

But we need more info to be able to help you..

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Johnny Lee avatar image
Johnny Lee answered ·

I am not sure what additional information would be helpful? Can you let me know what would be useful to know?


I just want to maximize solar energy usage when available and minimize shore power draw.

Solar priority is a pretty common configuration option on other solar/inverters.


I did try using state of charge (90%) as a trigger dshore power disconnect. This way there would be DC current from the MPPTs trying to charge the battery. However, this had couple undesired behaviors:

1. During evening, the shore power would connect and disconnect every 20 minutes as the batteries charged up and down causing some appliances to reset.

2. If I had a lot of solar, charge rate + absorption time would charge the batteries to 100% such that current from MPPTs would stop - even if I had a load. It ends up pulling from shore power until the absorption timeout.

If there is another way to do this, I am happy to try. But currently, I do not have reliable way to simply reduce my shore power draw when solar is available.




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JohnC avatar image JohnC ♦ commented ·
@Johnny Lee

Ok, what you want to do isn't unusual. And it's great you've tried already. If you come up against these little issues they can often be solved or worked around. Take for eg the 2 'behaviors' you've raised..

#1 Some appliances are so sensitive they shouldn't really be sold. But there's a setting in the Multi, 'Dynamic Current Limiter' which will bring in Shore gradually over a few seconds, like a soft-start. You could try that.

#2 This is possibly the Multi continuing on in Absorb when the mppts have dropped to Float. Do you really need the Multi do do Abs at all? Like could you just set a flat V, slightly less than mppt Float, so the mppt will always dominate.

And you could also use V as well as SOC to switch in Shore. I'll let you chew on this rather than explain, but it could be used to indicate when solar is producing or not, and terminate Shore when appropriate. Might be a bit trickier to do with Li's, but you haven't stated batt type.

You could also limit Multi charge rate to minimize cycling between an SOC range. Think smooothing..

Lots you could try, imagine what you really want and have a go. Don't let the little things annoy, come back and ask. Plenty of people here happy to share their own ideas and help with yours.



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