Download Model: BC-12b Switching Type Dual Source Battery Management

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Model: BC-12b
Switching Type Dual Source Battery Management System
VLF Designs
1621 Bella Vista Dr.
Jackson, Mo. 63755
[email protected]
Functional Description
The BC-12b is a complete battery management system utilizing analog and digital processing for
accurate charge control. The power sources for the BC-12 are both solar panel and line operated DC power
supply. The BC-12b features temperature compensated charging of 12 V lead acid batteries and an output
voltage limiter to prevent damage to equipment from high voltage (low temperature) charging. In addition
there are 2 independently adjustable low voltage disconnects in order to maximize run time of critical loads
during periods of adverse power input. All inputs and outputs are transient suppressed. All outputs are over
current protected by self resetting thermal fuses. All inputs and battery connections are protected by means
of automotive ATO type fuses.
Solar Input Voltage Maximum: 22 VDC
Input Voltage Minimum (for charging): 14 VDC
Solar Panel Input Current: 7A max per panel
DC Power Supply: 15-18 VDC
DC Input supply current limit: 4A Max.
Charge Voltage Range: 13.3 to 13.9 VDC at 70˚F (adjustable)
Charge Voltage Set: 13.7 VDC at 70˚F
Charge Temperature Coefficient: -12mV/1˚F
Post regulator Voltage Range: 12.0 to 13.1 VDC
Post Regulator Voltage Set: 12.9 VDC
Non-essential Load Disconnect Voltage Range: 11.4 to 12.4 VDC
Non-essential Load Disconnect Voltage Set: 12.4 VDC
Non-essential Load Hysterisis: 200 mVDC
Essential Load Disconnect Voltage Range: 11.4 to 12.4 VDC
Essential Load Disconnect Voltage Set: 11.9 VDC
Essential Load Hysterisis: 400mVDC
LVDC Output Current: 1.1A (other values available)
Reverse Battery Polarity Protection: 15A non reset fuse(ATO auto style)
Solar Panel Fuse: 10A (ATO auto style)
Power supply fuse: 5A (ATO auto style)
Theory of operation
Input power from the solar panel is routed through F2 to the shunt switching charge regulator. Input
power from the DC power source is connected through F1 to a series switching charge regulator. The outputs
of both regulators are combined in a common cathode Schottky type rectifier.
A yellow LED will illuminate for solar power source input voltages over 14 VDC and indicate that the
source is capable of charging the battery. As the battery approaches full charge the yellow solar panel LED will
dim indicating that excess power from the solar panel is being shunted to ground.
A green LED will light when an AC derived DC power supply is connected to the BC -12 management
system and is receiving sufficient power to charge the battery. The series switch is current limited to protect
the external power supply and prevent it from going into fold back current limiting under normal conditions.
The standard switching type power supply 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 4A to
protect the external supply from damage in the event of a deeply discharged or defective battery. When used
only with an AC power supply, the BC12b will not supply power to the load until a battery has been connected.
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 2A. The red LED is on for high charge rate(equalize) and dark in 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 charged, charging will begin in the equalize mode as soon as the solar
panel is capable of supplying at least a 2A charge current or if the AC operated DC power supply is connected.
The battery will receive the sum of the current the panel and power supply can provide until the battery
voltage reaches approximately 14.1 VDC (at 70˚F). Equalize 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.
Following the charge regulator is a post regulator stage. Its function is to limit the output voltage to
prevent damage to the load when batteries are being charged under very low temperature. It is a very low
dropout MOSFET series type regulator. However, when the battery voltage drops below the regulator setting,
the output will track the battery voltage within a few 10’s of milivolts. This regulator is normally set at
12.90VDC, thus allowing assessment of the battery state of charge during the night when no solar charging is
occurring. The regulator may be set to a lower voltage when it is used with analog radio equipment whose RF
output power varies with applied voltage.
Two almost identical low voltage disconnects (LVD) are provided in order to maximize the ability of a
system to record data under low solar conditions. The non-essential LVD is normally set at 12.2VDC (25%
remaining charge).It has approximately 200mV of hysterisis; thus this output will not reconnect its load until
the battery voltage rises above 12.4 VDC. This output would be used to power data communication
The essential LVD is set at 11.9 VDC (5% remaining charge) with approximately 400mV of hysterisis.
This LVD is normally used to power the digital recorder and its sensor(s). Most modern digital recorders have
sufficient internal memory to record in triggered mode for at least a month, thus hopefully precluding the loss
of data.
The low voltage disconnect thresholds are unaffected by temperature. Both outputs are protected
against reverse polarity and overvoltage transients. Polyfuses are 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 fuses are 10A for the solar input and 5A for the dc
power supply input.
Inputs and outputs from the regulator are by means of banana plugs and jacks. The banana plugs
supplied with the unit do not require soldering. Place a ¾” stripped wire though the insulator and then though
the hole in the banana plug. Twist the wire CW (as viewed from the back) and then secure it by screwing on
the insulator cap tightly.
The AC/DC power input to the BC-12 is by coaxial 2.5mm DC power jack (center terminal positive). The
BC-12 case is connected to circuit common through the power jack. Input power common and solar panel com
as well as load common and battery common are all connected together inside the case.
When the system is used with two solar panels, the power supply output plug should be unplugged
from the input to the BC-12b regulator to minimize power loss from the 2nd solar panel.
AC current limiter
The ac current limiter is set with a deeply discharged battery (11.9-12.1v), (or precision load)
connected to the battery terminals through a 10A DC ammeter. Set R40 fully CCW and plug in the dc power
supply. Adjust R40 CW for a reading of 4A 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 across the battery terminals.
Connect a 15 VDC power supply to the power supply input. The corresponding green LED should light and the
red full charge LED will be dark. Temporarily connect a 12V battery across the battery terminals to start the
regulator. Remove the battery and adjust R13 for the desired float charge voltage (given in the table below).
Interpolate the values in the table for other values of temperature.
Float Voltage Table
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
Post regulator adjustment
Connect a DC power supply set for 14VDC to the battery terminals. Set the post regulator adjustment
R29 for the desired voltage at either one of the LVD load terminals. The regulator may be set for voltages
below the LVD 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.
LVD adjustments
Connect the DC power supply set for the desired non-essential LVD threshold voltage to the battery
terminals of the regulator. Turn R37 fully CCW, and then adjust R37 slowly CW until the blue LED on the nonessential load is extinguished. The factory setting for this adjustment is 12.4 VDC. You can then increase the
power supply voltage until the blue non essential load LED just lights. This is the reconnect voltage and can
only be changed by a component change in the regulator.
Connect the DC power supply set for the desired essential LVD threshold voltage to the battery
terminals of the regulator. Turn R34 fully CCW, and then adjust R34 slowly CW until the blue LED on the
essential load is extinguished. The factory setting for this adjustment is 11.9 VDC. You can then increase the
power supply voltage until the blue essential load LED just lights. This is the reconnect voltage and can only be
changed by a component change in the regulator.