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June 6, 2023

12 volt power supply and DC UPS controller for use in cars and buses, 5 amp 4A charge rate

12 volt battery charger and UPS for cars, 5 Amps

Automotive battery backup controller.
12V DC UPS module charges a 12 volt battery and switches to the auxiliary battery when the main power is lost. This model offers a higher charging current than the other UPS control modules that we offer.

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We have several models of the DC/DC auto UPS control module. This one is similar to the 5A controller, but has a higher 4A charge current. It is designed for 12 volt systems, and has a throughput of 5 amps.

This is a microprocessor controlled uninterruptible power supply control module. You can connect the module to the car's electrical bus and it will charge an external 12 volt lead acid battery of your choice. Your equipment, for example, 60W small computer, video recorder, or a car alarm, is connected to the module. This equipment runs off the automobile's electrical bus until the voltage from the car drops below a preset voltage, the "N" voltage (from 13.1 to 11.9 volts, depending on your needs). Then the external battery takes over. When the external battery drops below the "P" preset voltage (Between 10 volts and 3 volts depending on your requirements) the power is cut off to either prevent damage to the external battery or to run your equipment as long as possible.

These controllers can charge an auxiliary battery from the car's alternator system or SLI (starting, lights and ignition) battery.

The auxiliary battery is isolated from the car's electrical system so that it will only operate the equipment attached to the load terminals of the controller.

The load terminals power your equipment from either the vehicle or the auxiliary battery, acting as a battery backup (BBU). The switch position depends on the voltage levels of the two inputs. This allows your equipment to be powered from the car when car power is available.

The DC UPS controller protects the auxiliary battery from being over-discharged.

The control set-points of the DC UPS controller can be set so that the equipment switches to auxiliary power when the car is shut off. It is not necessary to run an extra sense wire to the ignition, voltage sensing takes care of the decision making.

The BBU detects the vehicle's electrical bus voltages, so does not need an extra wire to connect to the ignition. The set-points can also be set so the the crossover voltage is lower, say 12.0 volts. This allows the load to run off the car's battery but cut off while the car's starting battery still has enough power to safely start the engine.

One of the most popular applications is to run a small appliance such as a refrigerator from a separate battery when the engine is off.

Model Price for quantity 1-49 Price for quantity 50-99 Quantity 100-499 Quantity 500+
PST-UPS4 $160
$140 $120 $95
DIN Rail mounting kit (see below) $6.00
$4.20 $3.80 $2.95
Detailed Specifications PST-UPS4
Max Charge Current 4A
Charging can occur with input voltages 10V to 15V
Maximum pass-through current 5 amps
Maximum pass-through wattage 60 watts continuous
Type of battery charged Lead acid, VRLA, SLA, etc.
Nominal Battery Voltage 12 Volts
Battery Capacity 0.8 to 33+ Amp-Hours
Size of module
External battery connects when the input voltage to the module drops below 12.5 volts
External battery is disconnected from the load when the external battery's voltage drops below 10 volts
If needed, the available custom set-points are Main On, Main Off, Charger On, Charger Off, Aux On, Aux Off This document describes how to engineer and specify the 6 custom set-points if desired
Temperature Minimum ambient temperature -10°C (-40°C available upon request)
Maximum ambient temperature of 70°C
Power Connectors Flying leads
Wire colors
Designator Color Gauge
Main input red 18AWG UL1007
Main ground black  
Load yellow  
    18AWG UL1007
Battery positive white  
Battery negative blue  
ADC ground grey 22AWG UL1061
ADC main voltage green  
ATC battery voltage orange  
The ADC feature consists of two voltage dividers, one for the battery voltage and the other for the car voltage. It is not required to use this feature, in which case the three wires can be cut short. The purpose is to reduce the voltage measured to be within the range of some analog to digital converters. The voltage measured is proportional to the vehicle or auxiliary battery voltages. They each measure 3.28V when there is 15V input.
Dimensions 70 x 108 x 23mm
2.75 x 4.25 x 0.90 inches
See drawing below
User's Manual PST-UPS4 12V to 12V DC UPS User's Manual
Theory of operation 5A DC-UPS Theory of Operation
Country of Origin Made in USA, NAFTA eligible

The PST-UPS4 can be ordered with a range of "N" and "P" values, as explained in the following table.
Suffixes* Voltage at which car battery is cut of from the load Voltage at which auxiliary battery is cut off from the load Why?
N13.1 (most common choice) 13.1 ±0.2 volts   Load is disconnected from the car electrical bus when the ignition is switched off
N12.9 12.9 ±0.2 volts    
N12.8 12.8 ±0.2 volts    
N 12.7 12.7 ±0.2 volts    
N12.6 12.6 ±0.2 volts    
N12.0 12.0 ±0.2 volts    
N11.9 11.9 +0.1 -0 volts   Allows the load to be powered by the car battery most of the time but still start the car (barely).
N?? Tell us what you need, the range is between 13.1 volts and 11.9 volts. The tolerance is ±6 mV with 2% accuracy    
P10 (most common choice)   10 volts When deep cycling of the auxiliary battery is desired.
P8   8 volts When longest possible system operation is desired regardless of loss of auxiliary battery cycle life.
P??   Tell us what you need, the range is between 7.5 to 14 volts The tolerance is ±6 mV with 2% accuracies  

Hook up diagram:
Connection diagram

dimensioned drawing of the PC-DC-UPS-1212-Nxx-Pyy
Dimensions, but the connections for the PST-UPS4 are wire leads.

The charge current depends on both the car voltage and the state of charge of the battery. When the car is running the blue curve applies.

din rail mount Din rail mount
DIN rail mount from the bottom DIN rail mount system viewed from the bottom

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