Hi, we could use some help in repairing a big APC UPS. Some time ago, we acquired two SURT3000XLI units, but actually both turned out to be defective. Does anyone here have experience with repairing such a beast, or access to a service manual or schematic they would be willing to share? I searched around the net but failed to find anything useful. Schematics for some smaller (consumer) UPSes are available, but nothing that would help with the big ones. The first one of our SURT3000 units shows odd symptoms: it apparently does everything it should, and never displays any error on its front panel. However, it also never charges its batteries. It correctly detects presence of the mains voltage, apparently switching to battery when necessary and (apparently; as indicated by the front panel) switching back once mains becomes available again. However, the load is always supplied from battery only; it is as if the unit always runs on battery, no matter whether mains is present or not. Once the battery modules get discharged to around 92VDC (~188VDC for the two in series), the UPS turns off just as it should. However, if left in this state even with the load turned off, the unit fails to charge: input wattage is way too low (~40W or so), and the battery voltage never goes up again. The only means to get it going again is by charging the batteries externally; i.e., dismantle the modules and charge each of the 16 lead batteries on its own. Each individual battery can still be charged, so I assume these are all fine and the fault really lies with the charging circuit of the SURT3000. The unit also had two of its on-board fuses blown (deep beneath the heat spreaders, so never intended to by field-servicable...). We exchanged them, together with two apparently-blown MOSFETs and the H-bridge. The fuses stay fine now (with the bad MOSFETs, they would blow instantly when turning the thing on), but the batteries still do not get charged. According to the APC forums, the SURT3000 series actually has a "known charger fault"; it shares it with the larger SURT5000 series, as the two use the exactly same mainboard. But unfortunately, details on this fault seem to have never been published. There is a revised model, SURTD3000XLI (note the "D"), in which this error should have been corrected. But trading the defective unit in for a replacement is currently out of the question; budget reasons. As for our second SURT3000 units, it seems to be completely shot. It turns on, but when trying to switch to battery power as part of the normal startup, it draws so much power that the house fuse blows (even the "more-lazy" one another fully-functional 3kVA UPS runs on). I think we are going to scrap this unit completely, but as the other one basically seems to be still alive, I had hoped that it could be repaired. TL/DR: does anyone have a schematic for the APC SURT3000XLI UPS? Any help would be greatly appreciated. SilverBull
It's usually better to send them back for a replacement battery service or trade-in with new warranty. The batteries do go. You can buy a new battery, but it's often as expensive to do so as it is to send it back to APC.
Thanks, retro. Replacing the batteries was actually the first thing we did. When I last checked, a set of two replacement battery cartridges cost less than 50% of a new SURTD3000 (even when considering the discount from trading in the old UPS). A set of 16 replacement batteries is even cheaper. As I wrote, we can charge all 16 batteries separately using an external charger. With fully-charged batteries, both cartridges are at their floating voltage, the UPS reports maximum battery capacity, and it is also able to run our test load for the anticipated time. So I assume the inverter is still fine. The unit just never recharges the batteries, or even maintains their charge while mains power is present. It always runs on battery; although it detects the presence of mains power correctly, it simply does not use it for anything. Something else is also odd about this unit: if mains power is present, the runtime seems to be a bit longer; just as if it tried to draw some power from mains, but fails (and without reporting any error, of course). The increase in runtime is barely noticable, though; maybe 5 minutes at a 120W resistive load (lightbulb).
