I have an Minuteman XRT1000 UPS. This unit has been sitting for quite some time, along with one one external XRTBP1 battery. I recently took the ups out of storage to use it and the ups is giving errors that the battery pack is bad. I opened up the case and indeed all of the batteries have broken cells. According to minuteman, these are not user replaceable batteries but i would like to replace them myself anyway. It takes four 12volt 18amp batteries, which I have only been able to find in available one place. I am wondering if it would be ok to either downgrade to a 12volt 17amp, or upgrade to a 12amp 20volt?