Overload inverter bypass.

dragonfly

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Aug 7, 2019
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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.
 
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.
 
Thanks, that's reassuring, is there away to tell wethers it is the large transformer model?
 
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 :)

If you go SSR make sure its not a "china"-ssr. it wont live long :p
 
I've hear that about Chinese SSR before, anybody know a good genuine supplier, in UK or Europe?
 
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.
 
not2bme said:
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.
 
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.
 
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.
 
Korishan said:
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.
 
Average joe uses it as inverter ONLY. No grid hooked up since thats not possible to control.

And I agree. UPS is either a UPS or standalone dumb inverter :)
 
I have used APC UPSs for the last 15yrs. In one case I tried to use a APC UPS 1500 for a large HP printer - and it would overload everytime the printer 'fired up'. After (maybe) 50 overloads it blew the APC. Based on this, I wouldn't design a system that had regular/ongoing overloads.

I love APC UPSs - I have 2 of the 3000 models with my own 7p7s 18650 battery packs in them. I use them to smooth the twice daily Inverter On/Off +automatic-transfer-switch cycles of my off-grid system. Their output wired to subpanels to parallel 120v plugs thru the house to various electronics (computers, TV, even the K-Cup coffee maker because it has a clock/auto-turn-on) and as mentioned, they have internet cards where they can monitored/managed at a central computer area.

One of the downsides is that they burn 40watts/hr, 24/7, just turned on sitting there. In my case, with 2 of them, that's 1.920kwh per 24hr day - or about 5% 'loss' of my PV power per day in summer - so not very efficient.
 
40w is nothing... Mpp is 60-80w per phase... So for me thats 240w Idle Lost hehe
 
Well I now have my hand on the UPS, its an APC SUA2200 (230v model) off approx 2005 vintage, so no LCD screen, just a few LEDs on the front.

I've pulled the batteries, and diagnosed that one of the 4 batteries, is bulged, and self discharging. So technically I could fix it for about 40 but that would only give me approx 2-3hrs runtime on my anticipated load. However I i replace the batteries with 4x 100ah batteries, I should get nearer the 24hrs I'm looking for ideally. Next issue is according to the manual the originally batteries were recharged in 4hrs, so I guess this would be also like 24hrs to recharge with the new batteries. I need to get this down to a maximum of 6hrs (i.e. well within the overnight cheap electric). I haven't looked up whether the batteries are wired at 24v or 48v yet, but I know they are in 24v packs. So to charge a 100ah battery pack, that is 50% discharged, to full in 6hrs, will take atleast a 20a battery charger (preferably multi stage), either 1 x 48v or 2 x 24v depending on the wiring. Can these be run in tandem with the APC charger or will they interfere with each other?
 
dragonfly said:
Well I now have my hand on the UPS, its an APC SUA2200 (230v model) off approx 2005 vintage, so no LCD screen, just a few LEDs on the front.

I've pulled the batteries, and diagnosed that one of the 4 batteries, is bulged, and self discharging. So technically I could fix it for about 40 but that would only give me approx 2-3hrs runtime on my anticipated load. However I i replace the batteries with 4x 100ah batteries, I should get nearer the 24hrs I'm looking for ideally. Next issue is according to the manual the originally batteries were recharged in 4hrs, so I guess this would be also like 24hrs to recharge with the new batteries. I need to get this down to a maximum of 6hrs (i.e. well within the overnight cheap electric). I haven't looked up whether the batteries are wired at 24v or 48v yet, but I know they are in 24v packs. So to charge a 100ah battery pack, that is 50% discharged, to full in 6hrs, will take atleast a 20a battery charger (preferably multi stage), either 1 x 48v or 2 x 24v depending on the wiring. Can these be run in tandem with the APC charger or will they interfere with each other?

You can charge the batteries from more than 1 source. The additional sources can be grid -> dc or solar etc. But you don't want to overcharge or the APC will sound alarm - so you need to find a compatible charging system. I'm not up on all the options but for example a cheapmpt-7210a (like this https://www.amazon.com/dp/B01HCL7LEW/) is settable so you can choose a good output (max) charging voltage and can do up to ~ 10a @ 24v... maybe 2 of them to get you to 20a. You can power it from a 120v -> DC powersupply (grid) or from solar panels.
 
Thanks, I think whatever I use, has to be cheap, if charging costs much more than 100, then I might as well bite the bullet and just get anmpp inverter, I probably only need something like 300woutput, and they do something like PIP1012MSE for under 200USD just they take your eyes out with the postage on top.
 
dragonfly said:
Thanks, I think whatever I use, has to be cheap, if charging costs much more than 100, then I might as well bite the bullet and just get anmpp inverter, I probably only need something like 300woutput, and they do something like PIP1012MSE for under 200USD just they take your eyes out with the postage on top.
Thempt-7210a are cheap and are a buck boost - e.g.dc input can be lower than battery charging output voltage (unlike most charge controllers) - and fully customize-able/settable.
There are a many youtubes on setup/operation - so you can see before you buy. Some downsides are thefan is noisy/cheapand they are not MPPT (not as efficient when hooked to a solar PV input).

I use one in my custom yeti - and it works great on both Renology Solar Panels and a constant DC power supply... so my yeti can power up from sun or 120v plug!
 
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