Testing a battery backup system under load conditions?
Testing a battery backup system under load conditions?
I own an older APC J25 power conditioner and battery backup. It is a 1500VA 865W model that was discontinued in 2022. The battery pack inside stopped working, and I have not managed to find the genuine replacement. APC advertises it online, but there isn’t a direct purchase option. One of our suppliers is a preferred vendor, yet they’ve also been unable to provide one for me.
The batteries inside are 12V9Ah units connected together with a block for wiring (to reach 24V) and fit into the housing. I disassembled the unit, separated the batteries, but the smaller 9Ah ones were hard to locate. A bigger battery wouldn’t fit, so I used two 7Ah batteries instead. My experience suggests this would have reduced runtime and didn’t cause any other problems.
Well....problem.
I recently upgraded my main rig (11900K, SF750 Platinum, RX 7800 XT) and since doing so I’m experiencing intermittent black screens with no video failure during gaming. The PC doesn’t display any error codes except for 41 AFTER hitting the power button to reset. It becomes unresponsive otherwise. The backup unit has a self-test that passes, showing load and runtime, and aside from a few minutes of reduced performance before failure, everything seems normal. I had three PCs running from the conditioned power—two at once while working, and one gaming rig alone. The other systems are a 10th gen i3 and an 8th gen i5 without dedicated graphics, which isn’t much for drawing.
I removed the gaming rig from the backup and connected it directly to the wall outlet, using the larger power cord that came with the PSU. The black screen issue has stopped since then, not because it was a frequent occurrence.
To summarize, is there a method to load test a backup with a known load (possibly artificial) so I can determine if the backup is the cause?
I have a large collection of incandescent bulbs that works well as a simple load tester. You can adjust the wattage by adding or removing a few bulbs. There are boxes with 150W bulbs, some from the 60s and a few older ones for more precise adjustments. You’ll need to purchase vintage Edison sockets and connect them accordingly. Another choice is to obtain a real load tester or use big resistors. They are still produced, and you might find affordable variable sliders on eBay.
The resistor pack becomes costly rapidly. By the time I assembled it, it represents a significant expense for simply acquiring a replacement part.
Yeah, when you need something right away, it can be the worst. Sometimes schools sell them in large quantities at auctions at low prices. You really only need a few, as long as they don’t overheat. The smaller the resistance value you require, the less coil you need and the hotter that section becomes. So if you need more power, look for a lower resistance option. I believe the smallest I’ve found is an 8 Ohm, made in the 50s—around 1800W at 120V RMS, which would likely melt it. A pair of 25 Ohm in parallel could help distribute the heat better, depending on your budget.