Nope. The self test runs every x number of hours (manufacturer defined). I don't think you can change it. In the power chute management software under device properties, diagnostic and self-test, you'll see when the last self test was done and the status. Some people don't like the APC self test because it totally disconnects itself from the power input and puts the full load on the batteries. If the batteries are defective (or the charging unit), the self test might cause the server to crash or unexpected shutdowns. I have to agree. APC should of designed something allowing it to sustain an equivalent load (under normal working conditions) to be used while it's on it's self test.
On another point. I just had a real world test of one of my upses and it failed miserably. I had a power failure at one of my sites and the APC1500VA tower ups failed within 15 minutes of outage. The last time I tested it was a year ago and it was able to keep the EXACT same load for 45 minutes. The self test didn't discover the problem but the power failure did. After the power came back, the UPS didn't even turn itself back on so someone had to manually power it up. 2 upses have died at this site (probably due to heat in the server room).
I also had a second UPS failure today but this one is not managed by me and don't know which manufacturer. This morning, one of my customer complained they couldn't access the server. After further testing on site, we discovered the UPS used by the building manager in their telecom equipment had failed. We didn't like the idea of having someone else take care of the equipment but we had no choice because all the network cabling in the building went to a shared telecom room for all the tenants. We only had 2 switches in that room but it was enough to cause us 2 hours of downtime.
I wasn't lucky today with UPSes and hopefully will have a better day tomorrow !