Battery backup system A case study
Background ! summer time blackouts
! solar rebates
! power independence
! reprogramming the Tivio!
Energy audit first ! what were the existing loads?
! what was essential and non-essential power circuits?
! when did they need the backup?
Sizing the PV and battery bank ! how long are the blackouts?
! do they have another form of generation (ie. genset)?
! is “UPS” functionality important?
! where will the battery bank go?
Location of equipment ! UPS inverters are generally not outdoor rated
! battery life is extended if cell temperatures are moderate and even
! cable runs between equipment
DC coupled system
AC coupled system
AC coupled system
! 10kWh of usable storage
! PV input approx. 12kWh/day in summer
! 24V 600Ah VRLA battery bank
! 3500W SP Pro inverter
! Flexmax 80 MPPT
System specification
! Battery type - lead acid (sealed/flooded), Lithium Ion, Lithium Iron Phosphate, other…
! Cycle life of battery
! Maximum depth of discharge
! Maintenance requirements
Design considerations
World’s worst UPS system!
World’s worst UPS system!
Major safety issues
! No battery isolator
! No cable support or protection
! No warning signs
! No locked access
2.1kW PV with 24V 400Ah battery bank