Backyard Aquaponics
A place to discuss aquaponics

OK, had a PITA weekend and finally got some results, so I thought I'd share it with you.

Background : had a domestic 1500VA/750W rated UPS which used 2x 7AH SLAs. SLAs were dead after a few years of use, and I thought, hey, great option for backup power for air pump (using 40W thereabouts).

Actions :
1) had a few newish 12V 7AH SLAs lying about, grabbed two, hacked open the box, swapped the batts out. (confirm that the batts were reading less than 10V - so dead)
2) went and charged up the system - all looked good.
3) took it out to the air pump, plugged it all in, then turned off mains power.
4) about 1min later, the unit shut down and pump too.

OK... where to start then, I figured it couldn't have been the batts, maybe the UPS.

PITA part-- downloaded the software driver only to find out that the Serial Number is required for the UPS. (and the serial number stuck to the UPS is NOT what is required - apparently they sell the license to the software driver if you lose it).

The solution -- finally talked to tech support (and not sales), got told that the UPS wouldn't work right at loads below 100W, and would think there's no load, therefore to save the SLAs, the UPS would turn off. Workaround - put a 100k resister across nominated diode on board to lower the load rating of the unit so it'll stay on. Did that, and voila, works like a charm.

In fact, i'm writing this article running a laptop off the UPS right now, and it's been 30mins+ without any shutdown yet. [I had to put some putting into the piezo as its beeping is driving me nuts ]

Now I'll test out how long it runs for, and report that in my thead.

Cheers all. Side note : brand Hypertec.

Thanks aquanoob, this might be useful to someone searching UPS one day. I use a UPS for my back up system and it has saved my butt a few times.

yeah, i figure having a UPS which supplies 240V is fine, as long as the equipment power draw is small enough. I didn't count on the UPS electronics to work out if the device load was too small to bother with keeping itself on.

Anyhow, I gave up after 1hr 30mins of running the laptop. Packed it up for home and will test it out on the 25W (correction it was not 40W) air pump (30L/min) and see how long it will run.

Just in case, I'll put on the backup aerator into the fish tank.

I have a Powersheild Defender 1200VA UPS running a 20w air pump and it works fine. Lasts at least 4 hours.

yes nih, some UPS units don't have this 'load check' requirement, so won't turn off after a preset time. Also need to find out at what level does the UPS cut out, to prevent the total drain on those SLAs.

I'm hoping to get that same or slightly better timing too. Will report on the length of time it lasts on the weekend.

I have a problem (sudden shutdown) with my UPS. I checked the batteries but both are ok and the problem is still there. I checked all wires and other items but can't find any issue, what can I do in this condition.

What kind of load do you have on it and what is it rated for?

In supplying power in battery mode? One of my UPS used to shut down because it had a timer circuit in it, annoying little bugger with its shrill insistent beep.

I only found out about the problem of insufficient load on the UPS after talking to the technical support ppl. They recommended adding a 100k resister across a diode. It basically lowers the load detection threshold. You'd be best to ask your product technical support to identify what you could do too.