Figure 29, Overvoltage Protection For Battery - Trace Engineering PS Series Owner's Manual

Ps series inverter/chargers

Table of Contents

OPERATION

OVERVOLTAGE PROTECTION FOR THE BATTERY IN SELL MODE

Normally, the inverter will regulate the charging process of the battery by selling excess power into the

utility grid. The battery will receive a three-stage charge routine as previously described. If the utility grid

is not available (due to an outage or tripped AC input circuit breaker, etc.) or if the inverter shuts off, then

the inverter is not able to sell the excess power and the battery voltage will not be regulated, resulting in

possible overcharging of the battery.

Therefore, a separate control is required to provide overvoltage protection for the battery when an outage

has occurred. The PS Series Inverter/Charger with the optional AUX RELAY MODULE is designed to

control an externally connected power relay that would disconnect the solar array and stop the charging

process. The voltage and hysteresis (difference between opening and closing voltage) are both

adjustable. The external relay can be either a standard mechanical type or a mercury displacement type,

depending on the voltage and current required. The mercury displacement type relay is usually required

when the system voltage is 48 VDC or if the current of the solar array exceeds about 20 amps. Multiple

relays can be used if the solar array is divided into several source circuits (do not parallel relays for higher

current). Another option is to use a charge controller such as the Trace C40. For more on the AUX

RELAY MODULE, see page 128.

A typically wiring configuration for this overvoltage protection is as follows:

This circuit does draw a small amount of power all of the time to power the coil of the relay. Other circuits

are possible but may have other drawbacks. This circuit provides protection against overcharging the

batteries.

5 AMP

FUSE

AUX

RELAY

MODULE