Download Model: SR-5b Switching Type Battery Management System Rev:b 0

Model: SR-5b
Switching Type Battery Management System
Rev:b
07/2011
VLF Designs
1621 Bella Vista Dr.
Jackson, Mo. 63755
573-204-1286
[email protected]
Functional Description
The SR-5a is a complete battery management system utilizing analog and digital
processing for accurate charge control and low heat generation. It is primarily intended for use
with analog telemetry systems and sensors that require well regulated low noise power for
optimum operation. The power source for the SR-5a is normally a solar panel or line operated
DC power supply. The SR-5a features temperature compensated charging of 12 V lead acid
batteries and an output voltage limiter to provide a stable output voltage under all charging
conditions. In addition, there is an adjustable low voltage disconnect in order to protect the
back up batteries during periods of adverse power input. The input and output are transient
suppressed. The output is over current protected by a self resetting thermal fuse. The input
and battery connections are protected from reverse polarity connection by means of
automotive ATO type fuses.
Specifications
Charge Input Voltage Maximum: 23 VDC
Input Voltage Minimum (for charging): 14 VDC
Solar Panel Input Current: 7.5A max per panel (fused)
DC Power Supply: 15-18 VDC
DC Input Supply Current Limit: Adjustable (4A with recommended supply)
Charge Voltage Range: 13.3 to 13.9 VDC at 70˚F (adjustable)
Charge Voltage Set: 13.65 VDC at 70˚F
Charge Temperature Coefficient: -12mV/1˚F
Post regulator Voltage Range: 12.0 to 13 VDC adjustable
Post Regulator Voltage Set: 12.9 VDC
Load Disconnect Voltage Range: 11.2 to 12.0 VDC
Load Disconnect Voltage Set: 11.9 VDC
Load Disconnect Hysterisis: 350mVDC (other values available at time of order)
LVDC Output Current:0.75A (other values available at time of order)
Reverse Battery Polarity Protection: 15A non reset fuse (ATO auto style)
Theory of operation
Input power from the solar panel or power supply is routed to a series switching charge
regulator through a transient suppression network consisting of V1, D1 and R2,C1.
A yellow LED will illuminate for a charge power source input voltages over 14 VDC and
indicate that the source is capable of charging the battery.
When a solar panel is utilized for a charging source, the input current limiter should be
set to the fully CW position so that no current limiting from this type of source occurs. All units
will be supplied from the factory with the current limiter set to this position. Adjustment will be
required if the unit is to be used with a line operated DC power supply.
The series switch in the SR-5a can be current limited when used with an external DC
power supply to prevent it from going into fold back current limiting. The optional standard
(70W) switching type power supply that can be supplied with the unit is capable of producing a
charge current of up to 4.6A, however the internal current limiter inside the BC-12 limits
current from the power supply to approximately 90% of capacity (4A) to protect the external
supply from damage in the event of a deeply discharged or defective battery. Any type of
External DC supply can be used provided that the current limiter is set below the maximum
output current from the power supply.
A red LED indicates that an equalization charge sequence has begun. Termination of
equalization charge will occur when the battery voltage reaches an upper voltage threshold and
the charging current falls below 2.0A. The red LED is on for high charge rate(equalize) and a
green LED is lit in the low rate (float) charge mode.
The charge regulator is configured around a temperature compensated reference
supply using an LM34 as a precision temperature sensor. The output of the charge regulator is
normally set at 13.7VDC at 70˚F for sealed (AGM or gel) batteries. It provides a variation of
approximately -12mV/˚F in charge voltage. This compensation level is accurate for all lead acid
battery chemistries. However, If non sealed lead acid batteries are used (deep cycle marine) the
regulator should be set for 13.6 VDC instead of 13.7 VDC at 70˚F. to help minimize the need to
add water on a periodic basis.
If a partially discharged battery is connected, charging will begin in the equalize mode as
soon as the power source is capable of supplying at least a 2A charge current. The battery will
remain in the high rate charge condition until the battery voltage reaches approximately 14.1
VDC (at 70˚F). High rate charge will continue until the battery charge current tapers to under
2A. At this point the charger will revert to a lower voltage float charge mode. All of the above
mentioned voltage levels are a function of the temperature of the charger, and for best results
the charger should be located near the batteries so that they are both in an equal temperature
regime. This method of charging maximizes battery life and returns approximately 90% of the
battery capacity in the shortest possible time.
Following the charge regulator is a post regulator stage. Its function is to regulate the
output voltage to provide a stable voltage to the load under all charge conditions. It is a very
low dropout MOSFET series type regulator. This regulator is normally set at 12.10VDC.
However, when the battery voltage drops below the regulator setting, the output will track the
battery voltage within a few 10’s of millivolts.
The low voltage disconnect (LVDC) is provided to maximize battery life under low charge
conditions. The LVDC is normally set at 11.9VDC (5% remaining charge for load currents below
300mA with a nominal 100AH battery). It has approximately 350mV of hysterisis; thus the load
will not reconnect until the battery voltage rises above 12.25 VDC. R32 may be increased to
increase the hysteresis if desired. The low voltage disconnect thresholds are unaffected by
temperature. The output is protected against reverse polarity and overvoltage transients. A
polyfuse self resetting fuse is used to prevent damage to the regulator if an accidental short
circuit occurs at the output.
Non-resettable fuses are used for reverse polarity protection in the input and battery
circuits. The battery fuse will only open if the battery is connected in reverse polarity to the
charger. It is 15A standard automotive type plastic bodied fuse. The input circuit fuse is 7.5A
Connections
Inputs and outputs from the regulator are by means of a single 8 position Phoenix type
connector. Provision has been made to connect 2 batteries in parallel configuration to the
regulator. These batteries will be connected in parallel as soon as the connector is plugged into
the regulator. Both batteries should be in a similar state of charge prior to connecting them
to the regulator, otherwise damage to the regulator may occur as the batteries equalize with
one another. If batteries of dissimilar charge are to be connected to the regulator they should
be connected together in parallel for at least 15 minutes before they are connected
individually to the regulator. It is important that the polarities of each battery be correct prior
to connection as there is no provision for reverse polarity connection of one of the two
batteries relative to the other.
Input power common, battery common and load common are all connected together
inside the case. The case is floating relative to all regulator connections.
Adjustments:
Refer to Figure 1 for adjustment locations
AC current limiter
This adjustment should only be performed when the SR-5a is used with an external
power supply. The ac current limiter is set with a 2 ohm 50 watt resistor connected to the
battery terminals through a 10A DC ammeter. Set R4 fully CCW and plug in the dc power
supply. Adjust R4 for a reading of 4A (or 95% of maximum supply output current) on the
ammeter.
Charge regulator adjustment
Because the charge regulator contains a temperature sensor, the charger should be
allowed to come to the ambient room temperature prior to adjustment.
Connect a DC voltmeter and a 200-500 ohm resistor across one of the battery terminals
of the regulator. Adjust R9 for the desired float voltage according to the following table. The
float voltage may be interpolated linearly for temperatures between those in the table.
Float Voltage Table
Temp
90˚F
80˚F
70˚F
60˚F
50˚F
AGM Battery
13.46 VDC
13.58 VDC
13.70 VDC
13.82 VDC
13.94 VDC
Deep Cycle (non-sealed) battery
13.36 VDC
13.48 VDC
13.60 VDC
13.72 VDC
13.84 VDC
High rate charging may be verified by connecting a 10 ohm 25 watt resistor in parallel
with a 100,000 uF capacitor across the battery terminals. The red light should light for about 12 seconds and the output voltage should increase 400 to 500 mV above the float level during
that same period.
Post regulator adjustment
Connect a DC power supply set for 14VDC to the battery terminals. Set the post
regulator adjustment R30 for the desired voltage at the LVDC load terminals. The regulator
may be set for voltages below the LVDC thresholds, as these thresholds are determined from
the battery voltage not the output voltage. The factory setting for this adjustment is normally
12.9 VDC with no load.
LVDC adjustment
Connect the DC power supply set for the desired LVDC threshold voltage to the battery
terminals of the regulator. Turn R25 fully CCW, and then adjust R25 slowly CW until the blue
LVDC load LED is extinguished. The factory setting for this adjustment is 11.9 VDC. Then
increase the power supply voltage until the blue load LED just lights. This is the reconnect
voltage and can only be changed by a component change, (R32) in the regulator.
Figure 1: SR-5a Adjustment locations and parts layout