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Comment by smallerfish | Hacker News Reader

Tangent: can anybody recommend a hybrid invertor that can prioritize solar over grid _without also_ prioritizing battery over grid when solar isn't available?

Context: I have a solar + battery system for backup power purposes. We have long enough grid outages every so often that make it worthwhile, and I need to keep the batteries charged in preparation for those outages. However, 98% of the time the batteries are charged and the solar power is just being wasted (there is no grid tie back here); I'd like to actually use it. The invertor (which is cheap chinese) can prioritize "renewable over grid" and thus use the solar during the day, but in this mode it then uses the batteries at night, and recharges them from grid when it runs them down; this means lots of battery cycles and also potential for backup to be foiled if the grid goes down at the wrong time.

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Check out the EG4 specs from signature solar. They have been reviewed a lot by Will Prowse on youtube and it’s what I would buy.

Seconded. The thing I’m using here is basically an EG4 knock off and I copied the wiring from the Will Prowse EG4 3000W mobile solar power guide (linked under how to) - which makes me think it’s the same board inside.

I like that their 3K inverter works with a 48-volt battery bank. They seem incredibly low cost for the value.

I have a similar Growatt from siganture solar. I'm pretty sure they're made by the same manufacturer as EG4. The cheaper one can do it, in a solar > utility > battery priority mode.

But depending on your solar panel and consistent power draw, I'd maybe use the solar > battery > utility mode. It'll let you set a point to switch from battery to utility, the highest at 95%. That way when your usage is below your solar generation, you can still use the solar to charge the battery.

A bit more wear and tear on the battery, but even less solar wasted. Assuming you can handle the batteries only being at 95% if you have an outage. If your usage is less than your solar generation, could even set it lower.

I've been looking at something similar but different. My grid is fine, but I want to be able to use the batteries based on my time-of-use plan prices. I have less solar panels, but would want to charge my battery using grid power when prices are lower.

Sunsynk will give you what you want. You can define a minimum battery level, after which it'll switch to grid if there is not enough solar to supply the load. If there is no grid then It'll continue to use battery until a final emergency cut-off that shuts the whole system down.

The battery setting can be configured on a timer, so you can have different cut-offs for dulifferent times of the day.

Can't second this enough. I have a Sunsynk inverter here in South Africa where we deal with multiple-daily grid outages. So the priority is always set (based on time of day) to keep the batteries charged "just in case". If Solar can't provide enough juice, it sucks from the grid.

The whole thing is actually quite elegant. It turns "electricity" into this fungible thing like it was supposed to be in the first place. More pro points, you can plug in an electric-start generator and configure it to start automatically as needed in order to supplement the solar. Going further still, you can plug in a wind-turbine and have it blend it into this whole system.

Makes me wish I could install a wind turbine on my roof. A fair bit of solar, coupled with a little bit of wind suddenly makes your batteries go a really long way towards being fully off-grid capable.

Definitely check out Will Prowse on YouTube, and see his website here:

https://www.mobile-solarpower.com

He has spec'd out a lot of DIY Solar Packages and lists the BoM on his website.

Another option is Phocos. You can set the PV / grid / battery priority order.

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