Has anyone used UPS inverters before? - Page 1
Forum section: electronics / beginners

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 04:38:44 am
content: As in, an inverter, to connect to an external battery, that also has a mains socket, and will charge the battery..I bought a lot of faulty ones... Apparently, the switch over circuitry wasn't working...Now, if I JUST connect mains, sure enough, it doesn't switch to the output socket..However, if I connect a battery, and mains, it appears to switch the output between the mains input, and inverter just fine...But the question is, is this normal?I've just tested a second, and it appears to function as the first one did....Any input would be great... I was about to tear one completely down till I realised this...Also, the charger output won't output anything either, unless the battery is connected when the UPS is turned on... you can even disconnect the battery once its on, and the switchover circuit remains active, and the charge circuit still outputs 13.8voltsThanks!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 04:55:45 am
content: This was originally going to be a "trouble shooting" thread, but I'm not even sure there's anything to trouble shoot!?I might try and find some comprehensive instructions, or find someone who has used this specific range of UPS inverters...

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 05:10:08 am
content: I'm going to need to number these and test again I think...Two of the 1000watt inverters will in fact switch the mains to the output, even without a battery connected, but no lights on the front panel come on...

author: krish2487
author_rank: Frequent Contributor
timestamp: February 22, 2014, 05:22:20 am
content: Yes it is normal,The battery bootstraps the entire inverter logic, generally speaking.Which is why you are not able to see the output switch over from battery to AC incoming mains when you do not connect a battery.Ditto with the battery charger. It just affirms that the battery needs to be present to 'kickstart' the operation.Regarding your third post, I d say that those two are likely to be the faulty ones with a failed relay.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 05:24:25 am
content: Quote from: krish2487 on February 22, 2014, 05:22:20 amI'll go and re-double check, but I'm fairly sure these were switching to the inverter when the mains was unplugged as well...Numbering and testing time I think!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 06:03:23 am
content: The third 1000watt does the same.The switch over relay "defaults" to connecting the mains input on the back panel, to the mains output on the front panel (also via the big switch on the front)So, when the battery is not connected, the relay remains un-powered, and the mains is just passed straight through.The relay is obviously powered by the external battery, and the relay is energised when the mains is lost....edit: my original post was incorrect... the 1500watt I first tested acts the same as the three 1000watt.With no battery connected, the main switch on the front simply switches the mains input from the input on the back, to the socket on the front...So, these four all work the same as each other...

author: rexxar
author_rank: Frequent Contributor
timestamp: February 22, 2014, 06:46:38 am
content: What you're describing is normal behavior for UPSes. Like krish said, the logic is powered by the battery. Once you connect a battery, the charger kicks in, which is why everything still works when you remove it again; the charger is now powering the logic.I'm not sure what exactly you're trying to do. Are you trying to turn an inverter into a UPS, or are you trying to convert a regular (standby) UPS into an always-on type?

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 06:47:42 am
content: I'm trying to figure out if these are actually faulty

author: SeanB
author_rank: Super Contributor
timestamp: February 22, 2014, 06:51:04 am
content: Probably not, most likely the original batteries died and were not cost effective to replace. Buy some SLA batteries and use the UPS units with them, or go to the local scrapyard and get some old car batteries, and go to the camping suppliers or truck/trailer spares places and get some cheap battery boxes to suit, then use them that way.

author: rexxar
author_rank: Frequent Contributor
timestamp: February 22, 2014, 06:58:05 am
content: Quote from: SeanB on February 22, 2014, 06:51:04 amAll of my UPSes I got really cheap (or free) because replacing the battery wasn't worth the hassle to someone, or they just didn't know. When the battery goes bad after a few years, I think most consumer-types figure they might as well just upgrade the whole unit, and toss the old one on fleabay.I found some SLA's on clearance at walmart, I've got two in parallel on my UPS. I get almost half an hour at full load

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 07:06:33 am
content: These don't have built in batteries (obviously) and I believe were all warranty returns... so I'd assume the company would have tested them on return... seeing the 1500watt version still sells for $900...One of the 2000watt had a rattle inside, so before attempting to power it up, I dismantled it...Turns out someone had attempted to repair it before, so it was lucky I didn't just plug it in!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 08:45:33 pm
content: Alrighty,So now that I've decided that five of these probably work... how can I fully test them to make sure they do work 100% as intended, before I try to sell a few on?I'd most likely sell two of the 1000watt versions, and keep a 1000w, 1500w, and 2000w for myself, "just in case"Also, under what circumstances could/would someone think the switch over circuit was faulty? What would they have been using these for, and how can I test this myself?Another thing, the actual switch over is done by a relay, so the switch over time depends on the relay switching speed... are there any devices that would be extremely reliant on a fast switch over? I tried running a laptop, with no battery, and couldn't get it to drop out at all on switch over...

author: rexxar
author_rank: Frequent Contributor
timestamp: February 22, 2014, 09:12:40 pm
content: IIRC, switchover time is in the order of a few mS, and yes, it's done with a nice, chunky relay. There are some applications where the switchover time is critical, but I doubt that any consumer or hobbyist would ever encounter it. For the most part, you're relying on the caps in the device's power supply to keep it running for the few mS when there's no power.If you have a mission-critical device, you'd use an online UPS. Basically it's just an inverter that's always on and powered by the battery charger. When mains goes, the only thing that happens is the charger turns off, you've still got the battery, so there's no switchover time.I think most likely the batteries died, and like you, they thought it was broken because it wouldn't switch on with no battery connected.I would test the low battery detection, and dropout voltage. Might as well do a load test while you're doing that. Give it 60-70% load, and watch the battery voltage. As long as it cuts out below 11V or so, it should be alright. I'd also do a few mains power cycles, make sure the relay works properly.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 22, 2014, 09:23:52 pm
content: Quote from: rexxar on February 22, 2014, 09:12:40 pmI just can't imagine FIVE people returning them with the same issue, and the supplier not properly testing them before giving an exchange or refund...They will all pass the mains straight through with no battery connected, but don't display and LED indication of anything...I can fairly easily test the 1000watt inverters under 70+% load, for an extended period of time, as I have a 180amp, 13.8volt power supplyThe reason I thought one was "bad" initially, was because I was sold them as being faulty

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 23, 2014, 12:13:49 am
content: Plugged a hair dryer into the 2000watt version, measured 1500watts when running at 240volts mains voltage, 1400watts with the 230volt from the inverter...So, 70% of the rated load.Well... the UPS has 4ga power input terminals... 4ga cable is good for about 100-120amps... so after 5 minutes of 150amp draw, the cable was warm, and dropping 0.5volts along its length...I got sick of standing around waiting for the 10.5volt low voltage alarm to kick in, so I turned it all offNow its recharging the battery, and I'll go test again to time how long it runs for!

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 23, 2014, 02:24:17 am
content: Load tested the 2000watt with about 1400watts, flattened the battery down to 10.6volts in about 22 minutes (it was a 130ah, deep cycle car battery)So that battery is back on the charger, and now I'm load testing the 1500watt inverter at 1000watts, for a timed 20 minutes.. off a different battery... takes too long to recharge the batteries if they're totally flat!Edit: 1500watt inverter passed that test too

author: rexxar
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:03:05 am
content: Quote from: AmmoJammo on February 23, 2014, 02:24:17 amSounds good!As long as they switch over from mains correctly, they look like they're perfectly functional. I can only guess that most of them had battery issues, and rather than spend the time and money to debug or repair, they just gave the customer a new one.

author: AmmoJammo
author_rank: Frequent Contributor
timestamp: February 23, 2014, 04:10:01 am
content: Quote from: rexxar on February 23, 2014, 04:03:05 amRemember, the batteries are external, so if the supplier simply replaced the UPS inverter, the customer would still have the same issue

author: G7PSK
author_rank: Super Contributor
timestamp: February 23, 2014, 09:28:30 am
content: Most likely leased units for some office, they cant afford for critical time failures so they are replaced on a time basis. I used to get SLA batteries from an electrician friend who went around changing them every six months in hospitals emergency systems. Nothing wrong with the batteries other than they had been on float for six months. He was doing the same with bank's alarm systems but they were changed out every nine months along with all the light bulbs,