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Experiences with EPS systems
(lemmy.sdf.org)
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this post was submitted on 26 Oct 2023
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This question doesn’t make very much sense because ordinarily in a solar power system if you have grid power, your panels will feed your battery bank through a solar management device, and battery charger. And then any excess from charging would be turned into AC for your home and grid. If you are pulling enough the net flow of power is out of solar, into your home, and out of street, into your home, that’s all there is to it. You would be consuming power. Your battery system will not turn on if you have grid power and your solar will turn off, typically, when you lose grid power. How you have solar connected to battery, whether they are in line or disjoint systems, dictates whether you will have solar powering your home in a power outage. In a power outage to prevent back feeding to the street and endangering line workers, a manual or auto transfer switch must be thrown before your battery bank can energize your home’s power.
Another reason you almost certainly don’t want to have your battery feeding the grid, other than it being a bad and cost inefficient way of handing power, is that very few if any consumer grade inverter systems have the ability to perfectly sync phase, output clean sine wave (less of a big deal than the previous and next point), and also be aware of when the power goes out, so you can protect yourself and others in that event.
For lack of ground in UPS units, I’m also not understanding your question. Why would you lack a ground for a UPS? Even when the internal transfer switch is thrown into battery backup your ground will be shared and connected to your home. Ofc unless you disconnect it from the wall. Then, yeah if you care about a ground then you can always connect it to the UPS via the power plug, or also bond any connected devices to earth at home.
I expected this kind of answer because my solution isn't really DIY, but to clarify: I'm using an AIO unit (Ecoflow delta 2) It is a solar controller, inverter and battery in one box.
This unit has EPS mode that allows me to use it sort of like a UPS with a few caveats:
So my first question was specific to the unit I'm using. I'm trying to understand how exactly it manages 3 sources of power in EPS mode especially when solar alone cannot provide 100% of output requirements.
My second question was about solving caveat #2 above. I can plug a regular UPS to the AC outlet of EPS, but AC output on the EPS has no ground. I already solved that issue by grounding UPS separately.
So, I can’t help you here. I know nothing about this product but I will advise you to not trust it with providing you continuous power. I don’t think consumer units like this even the one LTT reviewed are meant to be run 100% of the time. No matter what their marketing claims. They are very compact, energy dense, and even with fans blowing air likely get too warm for their own good.
I understand the want to have a self reliance on power but this ain’t it chief.
There are sketching ground bonding adapters online that I wouldn’t trust.
The below is a total assumption of how this is constructed electrically. No guarantees. I would bet it has input from wall power, powering a dc power supply for the batteries. The batteries are also charged by a solar charge controller. This DC battery bank is then connected to a switchable inverter. The output from the inverter is connected to a transfer switch that has two inputs and one output. One input to the internal inverter, the other input to wall power. The output to the outlets it has on its face. When you are in “EPS” mode it probably forces the transfer switch to always connect the front outlets to the inverter if it senses no power on the dc charger side. Then it probably takes a second to switch that connection. I’d bet it’s going slow to make absolutely sure it is never connecting inverter out to your home’s power outlet. That way there is no chance of blowing up the inverter.
This is consumer grade technology. Real UPS does not have this downside. You would be better off salvaging a commercial grade UPS with no battery, getting a battery bank for it, and connecting a solar charge controller to the battery. It would at least be rated to work continuously under load. Some UPS have a green mode. You want this off so it is always inverting and always passing through to your device, it’s own generated power.
But this also sucks because you’re losing like 20% total efficiency on the 120/240v -> dc battery charger in the UPS, and inverter from dc -> 120/240 volt outlets.
I appreciate the reply. That makes sense and I fully agree with the criticism of my setup.
I'm in (probably) unusual situation for this community because I live in a city with extremely reliable power. Had maybe one outage longer than a few minutes in the last 5 years.
I also have whole house solar system without battery backup.
My idea with a small, of the shelf, system was to create a solar/battery system to use for critical components like my security system, network equipment and optionally garage fridge. Separate system, not hooked up to city grid except to recharge the battery if draw is more than its solar panel can provide.
That's why I can live with consumer grade stuff - worst case scenario and I'll just reconnect everything to city grid.