Setec ST20-II, ST35-II User Instructions

ST - II Series POWER SUPPLIES

USER INSTRUCTIONS

Introduction

These instructions detail the installation and operation requirements for the ST20-II & ST35-II
power supplies. These have been designed for operation in RV’s providing a DC power system,
with optional battery back up.

The units operate from 240Vac and provide an isolated 13.65Vdc output at 20A and 35A
respectively for powering the load and charging of batteries. All the necessary protection and
operating features for the load and batteries are provided. An optional DC input is also provided to
enable charging of batteries and powering of the load from an external +13.8V DC power source.

The units are fully enclosed ready for direct wall mounting. All connections are at the rear of unit
providing convenient wiring and installation. User access to all load and battery fusing has been
provided from the front of the unit.

Operation

Safety: Refer to the installation section before operating. Correct installation is the most critical
factor in ensuring the safe use of the power supply. If every consideration of these instructions has
been satisfied the power supply will be safe to operate.

Functional Diagram:

Figure 1 Functional Block Diagram

Page 1 of 11 Doc 019244

AC Input

DC External
Input

Isense

5 x Load

Outputs

Battery

Output

Fuse Panel

AC / DC

Power Supply

Vadj

Battery Low Voltage
Disconnect circuit

0.8A

Trickle

+ve

-ve

+ve

-ve

ST – II Series POWER SUPPLIES USER INSTRUCTIONS

AC/DC Power Supply: This provides an isolated 13.65Vdc output for powering of the load and
float charging of the battery. Battery current is sensed and monitored by the power supply to ensure
that the maximum charging current is not exceeded.

Battery Features: The power supply provides full battery management as per the following.

The power supply is a four stage battery charger with Boost (VBoost = 14.05V), Float (VFloat =

13.65V), Store (VStore = 13.25V) and Trickle charge modes to ensure long battery life.

Charging current is limited to a maximum of 10A (ST20-II) and 15A (ST35-II). This provides
optimum life for the batteries.

To charge at the maximum battery charge current above, ensure the load current plus battery current
is equal or less than the maximum output current. The charging current will be reduced in situations
where the difference between the rated output current and the load current (the available charging
current), is less than the maximum charging current.

Also note that the battery current sense is provided in the “Batt +ve” battery output. For this feature
to work, the load “+ve” and battery “Batt +ve” should not be cross connected. (Appliances should
not be connected to both the “Batt +ve” and “+ve” terminals of the power supply. Appliances
should be connected to the “+ve” and “-ve” load terminals).

Low Voltage Disconnection of the batteries is provided to prevent deep discharge of the battery.
Automatic reconnection occurs when battery voltage recovers.

Battery Current Drain is less than 2mA.

Trickle Charge to the battery is always present. When the battery voltage is below the LVD (Low

voltage disconnect) re-connect voltage (<10V and the mains power or auxiliary power is available,
the battery will be charging at 0.8A. When the battery voltage is sufficient (>10.5V for first power
up, 11.5V and 11.7V for subsequent reconnection with and without mains respectively) the LVD
will connect the battery and allow float charging at 10A/15A (ST20-II/ST35-II). The Trickle
Charge feature is provided to allow “very” flat batteries to be charged at a rate, which will extend
their life.

Auxiliary Power Input: The power supply terminal “Aux In +VE” provides an alternative option
for powering of the load and float charging of the batteries when mains voltages are not present.
This input is to be powered by a suitable +12V system. (i.e. CAR). The voltage of the auxiliary
power source should not exceed 14.8 volts.

When operating via the external input, current and voltage control for the battery must be provided
from the external source. The ST20-II/35-II does not provide battery current limit or voltage control
when operating in this configuration. Trickle Charge is still functional when powered through
“Aux In +VE” terminal of power supply.

Suitable fuse protection must be provided for this input. A fuse rating not exceeding 20 Amps for
ST20-II and 30 Amps for ST35-II must be used.

Solar power should be connected directly across the battery terminals with a voltage regulator in
series. A solar panel voltage regulator with maximum output voltage not exceeding 14.8 volts must
be used at all times. Failure to use a voltage regulator may result in power supply damage.

Generator 12 volt outputs should not be connected across battery terminal whilst battery is
connected to power supply or connected to the “Aux In +VE” terminal of power supply. Serious
power supply damage or internal explosion may occur. If a flat 12 volt battery has to be charged
using the generators 12 volt output, it should first be disconnected from the power supply. Once
battery has being charged it can then be reconnected to power supply.

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ST – II Series POWER SUPPLIES USER INSTRUCTIONS

Power supply unit should only be powered from either 240VAC mains or Auxiliary Power
(Auxiliary Power also includes solar power) but not both. Failure to do so may result in damage to
power supply.

Protection: the power supply provides automatic protection for overload including short circuit,
over-voltage, over-temperature and reverse connected battery. In such instances the Fault indicator
will illuminate and the power supply will shut down. It will attempt to automatically restart every 5
seconds until such case that the fault is removed.

Fusing: Each load circuit and the battery have been fused to provide fault protection and
discrimination. Refer to servicing section for maximum fuse ratings.

CAUTION:

This appliance is not intended for use by young children or infirm persons without supervision.

Young children should be supervised to ensure that they do not play with the appliance.

Power supply unit should only be powered from either 240VAC mains or Auxiliary Power
(Auxiliary Power also includes solar power) but not both. Failure to do so may result in damage to
power supply.

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ST – II Series POWER SUPPLIES USER INSTRUCTIONS

Installation

Host Equipment: The host equipment must ensure that access to the unit (other than the front
panel) by the user is prevented.

Personnel: Installation is to be carried out only by suitably qualified personnel.

Ventilation: Provide a minimum of 80mm clearance above, below and behind the unit. The final

enclosure must also provide adequate ventilation to the outside world (or larger internal cavity) to
prevent the build up of hot air. Failure to provide adequate ventilation will mean the unit may
prematurely trip thermal shut-down. A minimum ventilation of 20,000mm2 to the outside world
must be provided.

CAUTION

Do not install unit in same compartment as batteries or flammable material such as petrol.

Ensure that the installation meets the ventilation requirements above.

Mechanical and Mounting:

Depth of unit is 125mm

After mounting unit, clip on the front fascia (ensure that all locking clips have engaged) and secure
with screw located inside the fuse panel door.

Orientation: The unit is to be installed with the front fascia in a vertical plane. Failure to do this
will cause premature temperature shut-down.

Page 4 of 11 Issue F

112

2

BATT

BATT

33445

5

Fault LED

Fuse Panel Door

303.5

156.5

Four by 4.5 x 9mm
mounting holes at 129.5
(h) x 287 (w) centres.

Cut out for mounting
152(h) x 272(w)