So I have been pretty disappointed with UPS solutions for awhile. I feel as though they are over priced and often under deliver. Especially with the advances in battery tech being made on the solar side of things. I have an older line-interactive APC UPS that is pretty long in the tooth. I am seriously debating replacing it with a DIY solution using basically a solar charge controller/inverter and a battery bank to make a much higher KWh UPS for the same price or less.
Is anyone else doing this or something similar?
You could definitely go cheaper or more expensive depending on the features you want and the size of the system but this is pretty simple and easy to deal with and gives you a much more capable system than what you would buy from Eaton or APC for less money.
Just make sure you have the wiring done by a certified electrician, otherwise your insurance company will want to have a word. Or just flat-out cancel your home insurance
Depends on local code and laws. Most places you can do your own high voltage as long as it isn’t for commercial purposes and it meets code. Some places make you get a temporary work permit and get a final inspection from a code inspector.
Regardless it seems pretty straight forward for something like this. You could even just wire it into a 230v plug if you wanted and use an appliance plug.
What’s your plan for monitoring/alerting? A key feature of a UPS is alerting systems that the battery is running low and they should shut down. I saw only one solar charge controller on Network UPS Tools’ list of supported equipment and I suspect it’s an old model as I did not find it available for sale.
And testing? All decent UPSes do periodic self-tests to try and alert you that the battery capacity is insufficient before it fails.
If you’re charging from utility power, your batteries will be constantly charging with no load, possibly sulfating and degrading over time. You need to carefully design your charging system to match your battery bank to avoid overcharging and damaging them.
Your inverter has only 120V output, no split-phase option? Just about all computer equipment can be run from 240V, and it’s more efficient to do so.
Higher end charge controllers will alert you to equipment failures and power outages. I just listed a middle of the road unit but it does have network connectivity I don’t know what the extent of the features are though.
The batteries have a built in BMS that interfaces with the charge controller or you can set up a stand alone bms.
These units are literally designed to be full spectrum power management units to include maintaining the batteries.
This particular unit can do split phase if you have 2+ paralleled together. But frankly I just picked that unit as an example. There are certainly better/different options out there.
Point being that this is a much better value per KWh compared to a traditional UPS and has the advantage of being able to use commodity hardware in different configurations to meet your needs.
Honestly safer too. The battery pack I listed I my first post has redundant fire suppression systems in the case so if a lithium cell blows it can put itself out. And it is UL rated.
Your solution as linked would replace an offline ups, not a line interactive one
The Eg4 inverter only switches between line and battery, in 2 to 10 Ms, and does not do anything to the line input to protect from surges, over or undercurrent, brownouts…
Your solution would implement a 3000Va(roughly) ups whose batteries can sustain maximum output for 1.5 hours at 90%Dod instead if the usual 7 minutes…
To me, you would be implementing a different use case whose prices are not comparable because you are targeting different needs
Standard ups:
User installable and serviceable
protect from power surges
(on line and interactive) protect from under/over current
provide enough battery power to last 10 mins at maximum draw and provide an alerting system so that you can shut down stuff/get a generator online
Your solution:
provides enough battery power to last 1-more hours … More akin to a generator imho
So, if your goal is to get the maximum time on battery during outages, and you live in a place where grid power is stable, and if your equipment can handle a switch time of 10ms then there may be a point. If not, I would still use a smaller always on UPS that can stabilize the supplied power and buffer it from the switch from grid to inverter …
Oh wait, that is exactly how I am running
I went through your same thought process when installing batteries in my house, already had the ups and wondered about just selling it, my use case is slightly different as my inverter is an in-grid one, so the electrical side is more complex to meet code but still, I decided to keep it.
Mine is a 3000va always on unit that I bought for 650EUR from a local producer (Italy) it is not a name brand that would have cost me 2500eur during the civil shortage but it has serial monitoring, replaceable standard batteries and so far(touching wood) has performed as expected…
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