User Manual

GRID-CONNECTED BACKUP

There are two distinct uses for a grid-connected battery bank. The first,

and the most common is a power backup system. The purpose is to provide

temporary power in the instance of grid loss. This is simular to a UPS system,

but is typically on a much larger scale with higher storage capacity.

The second is a grid-tied system with battery backup. The purpose of this

system setup is to generate and sell excess power produced by a renewable

source to your utility provider when you are connected to the grid. In the

event of a grid failure, the battery bank then provides storage power for the

critical loads during the outage. Systems are configured according to how

much power is to be sold to the utility vs. how much will be stored. If a higher

percentage of the power generated is pushed to the utility, this will decrease

the remaining amount available for backup and vice versa. This may be

determined by personal preference or may be limited or regulated by the utility.

For grid-tied battery backup systems, the battery bank should only be sized

to handle the loads supported for the duration of a temporary outage. These

systems are commonly used to run household necessities such as limited

lighting, refrigeration, etc. It is important to limit the size of the supported

load to essential service only as higher capacity battery banks require more

maintenance as well as power usage to hold at full charge, reducing the

amount of generated power which can be sold to the utility.

Typically, because outages are infrequent and occur only a few times per year

in most regions, these systems are designed for greater depth of discharge

than off-grid. In some cases they may be designed to discharge as much as

20% state of charge over a relatively short period of time.

In areas where the grid may not be reliable and extended or intermittent

outages occur frequently, it would be necessary to size the battery bank

and charging source(s) to support a larger load over a longer period of time.

This would prevent the battery bank from over-discharging and/or insufficient

charging between cycles.