Summary: See the following user reported guide about the APC Back-UPS CS 350 BK350EI, as this one (BK500BLK) appears to have the same issue: http://forum.synology.com/wiki/index.php/User_Reported_Compatible_Uninterruptible_Power_Supplies
Pros: Seems to work plug and play with my Synology DS1513+. With just the NAS plugged in to the battery, at 100% battery I get an estimated ~2812 Seconds reported to Synology.
Cons: After simulating power failure by unplugging the UPS, I checked my reported battery level and within 1 minute I had dropped down to ~75% of battery. I tested it again and left it running longer, under 5 minutes (with the NAS in safe mode) and it only seemed to drop to ~65%. I thought that I had bought more than enough battery for my NAS power usage, so I'm left wondering if the UPS power levels are not reported correctly.
Summary: I've had my unit for a few years now. The battery has finally gone out. Easy replacement. I got a warning alarm from the unit that was telling that the battery needed to be replaced which is handy. Plugged in the new battery and it works fine. Unplugged the unit and my computer didn't even blink.
Summary: I have always used APC and NEVER had any problems. It's the only reason I pay their higher prices.
Pros: Easy install, no noises coming from the unit. Windows Vista detects it as a battery without the need to install the included software (please don't ask about the Vista). Can now image customer drives and make backups without worrying about power loss.
Cons: Very little room for transformers. I have a laptop, external HDD, and a HDD dock attached to the battery side. The dock and external drive have large transformers so a powerstrip was needed. (I don't like to plug one surge protector into another)
Summary: We have 14 of these backups, one on each workstation at our business. We've tried other backups over the years, but these are the ones that last the longest. And it's relatively easy to replace the batteries.
Summary: This is a nice compact unit. I like having the outlets on the back of the unit. One of my UPS units has the outlets on the top and they get dusty. I will replace it with one of these when the battery fails.
Summary: The backup power and surge protector came quickly and appears to work well. Only problem is that the plug receptacles on the back are a bit too close together so that plugs with transformers attached to the plug don't fit well and required some moving of plugs around in order to be able to plug the bulkier plugs into the surge protector.
Summary: I bought this UPS 16 years ago. I lived in the mountains 10 years, where we lost power constantly. It's performed great, although I don't leave my systems on. Filtering works great, it clicks letting me know it's caught a dip. Definitely got my money's worth. When the battery alarm went off (pay attention to this, the tops can pop if you don't), I got a new one (more power). This little UPS outlasted 3 computers before it came to end of life.
Pros: Clean power, dependable, outlasted any expectation and warranty, can recycle with trade-ups program, line filtering and RJ45 jacks
Cons: Heavy (but what UPS isn't). The end of life alarm is really loud! No real cons though.