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