Backup Time Reduced. Review on Microtek UPS Heritage Plus

I bought Microtek UPS Heritage Plus for my computer. It was nice feeling to purchase product from Microtek. As microtek company have great market response in power solutions but I realised very soon that only company name is not enough to deal with purchasing products. I used this product but my experience was not good with this product because at starting when I got this product it gave 20 minutes backup of power for my computer but after 1 month it started reducing backup time. Also I got some problem of fluctuation in power nd that was not stable. I complained for this product at service centre they changed its battery but problem again started of backup. Also it has a disgusting feature of beeping sound every 3-4 seconds that is weired. Beeping sound should blows only when baatery backup is near to be end. I didnot found this product good for computers.