Replacement battery (1) is available
5.4kVA/4.8kW double-conversion on-line pure sine wave 3U rackmount UPS
Ideal for servers, storage, voice/data networks, medical labs, and light industrial applications
Rack/Tower convertible (rail kit included)
Delivers clean power with zero transfer time for critical or sensitive devices
Add up to 10 external battery packs (SRT192RMBP) for extended runtime
Environmental performance of the product 
 
See more at:  https://www.apc.com/us/en/product/SRT5KRMXLT/apc-smartups-online-5-4kva-rackmount-3u-208v-2x-l620r+2x-l630r-nema-outlets-network-card+smartslot-extended-runtime-w-rail-kit/