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Overload inverter bypass.
#1
I've been offered a free dead 2200va ups. Death is the standard reason of battery failure. So I figure this is a good starting point for an inverter etc. And it will cover 95% of our power requirements, but we do have spikes of 3-6kw. As this is going to be mainly used for timeshifting our power usage until solar panels are fitted, I'm not too concerned about the lower than ideal output power, I'll just use it as proof of concept. However I need to deal with the spikes. Is there any simple way of switching back to grid, and bypassing the ups in an overload situation? I was thinking at something like 1500w, I can do it with an SSR and an esp8266 but I fear it won't respond anywhere near quick enough.
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#2
The 2200 model can handle quite a bit.

If it's the large transformer type, it should be able to handle up to about 3000 watt surge for several seconds.

I wouldn't worry about overloading, just limit the number of devices that are on it.
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#3
Thanks, that's reassuring, is there away to tell wethers it is the large transformer model?
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#4
An ESP 8266 can easily monitor the load and switch fast enough if needed. As Korishan said this should be able to cope with some load for shorter amount of time.
Since it is UPS you can only run it on battery with disabled Grid so the UPS itself cannot switch back. With that said test it.. Worst case if its good gear it will just shut down due to overload Smile

If you go SSR make sure its not a "china"-ssr. it wont live long Tongue
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#5
I've hear that about Chinese SSR before, anybody know a good genuine supplier, in UK or Europe?
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#6
I would think the UPS would have an overload protection so if you do exceed it the UPS would just shut down. In that case just install a ATS so your power gets trasfered to grid if something happens. UPS are tricky and I don't think anyone here's had much luck using it as an inverter. Some other issues including low voltage disconnect, over voltage faults, etc. It's just that it's built for lead acid and not for inverting 100% of the time. By the time you go and build all those little things to make it work, it's just easier to buy a proper inverter.
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#7
(09-01-2019, 01:08 PM)not2bme Wrote: I would think the UPS would have an overload protection so if you do exceed it the UPS would just shut down. In that case just install a ATS so your power gets trasfered to grid if something happens. UPS are tricky and I don't think anyone here's had much luck using it as an inverter. Some other issues including low voltage disconnect, over voltage faults, etc. It's just that it's built for lead acid and not for inverting 100% of the time. By the time you go and build all those little things to make it work, it's just easier to buy a proper inverter.

Yes, the UPS should have it built in. It should start beeping continuously until the load is released or the timer is reached, which ever is first. The timer could be 5 seconds, 15 seconds or 30 seconds. Depending on the amount of overload.

A UPS can be used as a standalone inverter. APC's are a bit easier to do than others. The ones that can handle the continuous loads are the server grade inverters, they have the large transformers in them, and usually 2 of them.

Some inverters can be programmed, so it doesn't matter if the power source is LA, LiFePO4, other Lithium based, or other battery chemistry. You can program the charge points. Not all can do this though.


For the ATS, all you'd need to do is monitor battery voltage/load, and if it goes too low (batt) or high (load) turn on the AC connection to the UPS. It'll think power is restored and switch over to Grid automatically internally.

But again, with this type of setup, I would only put certain things on the UPS load like electronics and lights. I would not put high demand devices like microwave, washer, dryer, dish washer, etc. Even fans would be fine as they pull little current.
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#8
I've never seen a UPS that you can set a max charge point. Not on any Eaton or APC one that I have anyways. Crap if the APC units had that option I would have set the damn float level lower, some of their units are notorious for setting too high that I constantly have to replace the batteries after 2-3 years. The Eatons have a better system that makes my batteries last 5-6 years.

I can see a low battery percentage disconnect, which is ambiguous at best. Nothing short of someone's managed to hack the firmware of a APC unit and turned it into a more programmable inverter, it's still just a poor hack job.

An ATS does what it does, if the main power is not available it transfers to the secondary, then back to main when available. You can find plenty of datacenter ones or marine ones where they use for shore/battery.
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#9
APC Server grade UPS units can be programed through the PowerChute software. This is the key point. It HAS to be server grade UPS, not consumer grade.

Check out AveRageJoe's videos as he's done this. He's actually running quite a bit of his house off of APC 3000 units. Granted, I think he actually charges the battery separately as he's also using Batrium. But before he got that, he did charge the batts through the UPS a few times for demonstration purposes.
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#10
(09-01-2019, 02:23 PM)Korishan Wrote: APC Server grade UPS units can be programed through the PowerChute  software. This is the key point. It HAS to be server grade UPS, not consumer grade.

Check out AveRageJoe's videos as he's done this. He's actually running quite a bit of his house off of APC 3000 units. Granted, I think he actually charges the battery separately as he's also using Batrium. But before he got that, he did charge the batts through the UPS a few times for demonstration purposes.


And i'm talking server grade as well. I've never seen a UPS where it allows you to control voltage points. I can't see how AverageJoe has managed to use it as a proper inverter. For example, how would you ever set a point, let's say 50V to go back on grid, and then only when the solar charges the battery and it reaches 52V to go back on battery?  Short term, and I mean for a one time manual operation use it's possible. But to have an automatic function that's reliable, no.
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daromer (09-01-2019, 03:18 PM), chuckp (09-01-2019, 07:58 PM), Solardad (09-01-2019, 11:42 PM), stevelectric (09-04-2019, 08:45 AM), ajw22 (09-01-2019, 10:13 AM), OffGridInTheCity (09-01-2019, 07:15 PM), 100kwh-hunter (09-05-2019, 04:41 PM), juanjo57 (09-01-2019, 06:38 AM), dragonfly (09-03-2019, 05:01 AM), w0067814 (09-08-2019, 07:24 PM), Ibiza (09-01-2019, 05:42 PM), Sean (09-01-2019, 04:02 PM), Korishan (09-01-2019, 03:39 PM), wim (09-01-2019, 05:14 PM), watts-on (09-03-2019, 09:10 AM), Geek (09-03-2019, 03:03 AM), not2bme (09-01-2019, 02:36 PM), Filip (09-01-2019, 08:21 AM), jm1 (09-08-2019, 08:22 PM), Cobra_Phil (09-02-2019, 05:04 AM)

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