Patent Application
20170207641
The present invention relates to a systems and methods for selectively connecting or separating a pair of batteries depending upon the state of the individual batteries and the charging system so as to maintain and preserve best condition of those batteries.
There are many vehicle applications in which there is a battery (primary) used for starting the vehicle and supporting its various electrical systems. There is also a system for charging that battery whenever the vehicle engine is operating. There are furthermore many applications for an additional (auxiliary) battery or bank of batteries to be used to support auxiliary equipment. Such equipment could be living quarters equipment on a recreational vehicle, a CPAP machine in the sleeper cab of an over the road truck or any other variety of apparatus that require electrical power. The electrical loads that draw power from the auxiliary battery may operate without distinction for whether the vehicle engine and charging system are operating or not. It is common to charge the auxiliary batteries from the same charging system that charges the vehicle primary battery. It is important to prevent the electrical loads that draw power from the auxiliary battery from depleting the vehicle's primary battery to the extent that primary vehicle functions cannot be supported, such as starting the vehicle. For this reason it is necessary to have a means to selectively connect and separate the primary and auxiliary batteries depending upon the condition of those batteries and the status of the vehicles charging system.
Additionally, as parts on a truck are subject to all the weather and bad roads that are experienced by the truck, damage and premature wear can be experienced by a contactor in control of joining and separating the batteries. Furthermore, contacting two direct current power sources creates a potential for a large current to spike across the contactor which could lead to premature wear of the internal components of the contactor as well. Therefore, the industry could benefit from a contactor assembly that is better protected from external influences.
Provided is a system and methods for separating batteries. The invention being directed to providing a contactor that is better protected from outside influences such as weather and road conditions and also from potentially large current spikes.
The present invention provides that the coil of the contactor is controlled by a bi-polar electronic driver with current limiting functionality. The design of the coil provides reliable latch and unlatch at voltages associated with highly discharged or damaged batteries and elevated ambient temperatures (that raise coil resistance) and furthermore with the electronic current limiting set to prevent the coil from generating Amp Turn levels sufficient to demagnetize the permanent magnet under conditions of high battery voltage and low ambient conditions (that lower coil resistance).
Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
The prior art contactor assembly 10 is used primarily for joining and separating a Main battery 30 (see
Although, the control circuit board (hidden) is shielded from most environmental events including corrosive elements, moisture, and liquid ingress over the entire life of the product by the electrical potting material 14, the bus bars 18 and the DC contactor coil connections 20 that electrically and mechanically join the control circuit board (hidden) to the DC contactor 12 are exposed to the environment and prone to corrosion or physical damage.
Corrosion of the bus bars 18 creates poor electrical sense interconnects and unpredictable voltage drops that affect the logic and control circuit's ability to accurately measure the voltages of the Main and Auxiliary batteries 30, 40 (see
Additionally, over the life of the product, corrosion of the bus bars 18 along with thermal aging and potting material fatigue creates voids (not shown) in the potting material 14 around the junctions 26 of the potting material 14 and the bus bars 18. The voids (not shown) become the primary path for environmental ingress to the control circuit board (hidden) which creates unpredictable device operation, complete device failure, or even provide low voltage ignition sources from unintended ground paths.
In addition to corrosion, the bus bars 18 are continuously exposed at battery potential and present a constant threat of being bridged by a conductive object to each other or chassis ground. Further, the exposed DC contactor coil connections 20 present a constant threat of being shorted to ground or disconnected.
The solenoid assembly 120 is preferably a bi-stable magnetic latching solenoid. The solenoid assembly 120 preferably comprises a coil assembly 122, a plunger assembly 130, a crossbar 144, an end cap 146, a pole washer 150, and a pair of half shells 154. The coil assembly 122 comprises a bobbin 124, a pair of coil terminals 126 electrically connected to the bobbin 124, and magnet wire 128 wrapped around the bobbin 124. The bobbin 124 is at least partially positioned within the end cap 146. The pair of half shells 154 are preferably positioned around the outside of the coil assembly 122 and in direct contact with the pole washer 150 and the end cap 146 to complete the magnetic circuit; however, this relationship is not visible in the cross-sectional view of
The plunger assembly 130 preferably comprises a first plunger part 132, a second plunger part 134, a magnet 138, and a cap screw 140. The magnet 138 is preferably a rare earth permanent ring magnet (NdFeB, Grade N42M) and is sandwiched between the first plunger part 132 and the second plunger part 134. The first and second plunger parts 132, 134 preferably comprise low carbon steel and are physically joined by the cap screw 140, which is preferably made from non-magnetic stainless steel. The plunger assembly 130 is located mostly within the bobbin 124 with the second plunger part 134 closest to the end cap 146.
A plunger shaft 136 preferably extends outward from the first plunger part 132 and through the pole washer 150 and a seal spring 156 and terminates with attachment to a head spring 158. The crossbar 144 is mounted to the plunger shaft 136 between a retaining clip 196 and seal spring 156
Contacts 160 are placed on the crossbar 144 and the triangular heads 114, 118 of the first and second studs 112, 116, respectively. The contacts 160 preferably comprise silver cad oxide chips and are silver-brazed onto the stud heads 114, 118 and the crossbar 144. The studs 112, 116 are rotated such that the center to center distance 162 between contacts 160 is minimized. This in turn lowers the material usage in the crossbar 144 and thereby reduces the crossbar's 144 total mass. The silver cad oxide material is able to handle high closing currents, which are expected in an application of connecting two batteries charged to different levels. However, other materials exhibiting the same characteristics are also contemplated.
It should be noted that a through-hole 152 in the pole washer 150 is preferably sized large enough for the plunger shaft 136 to pass through without excessive loss of force due to non-force producing flux leakage.
A coil o-ring 164 is positioned between the bobbin 124 and the pole washer 150 and is compressed as needed to take up any dimensional tolerance stack ups and also to minimize movement from vibration. The o-ring 164 also biases and maintains the bobbin 124 to its proper position in the solenoid assembly 120.
The cap screw 140 has a cap screw head 142 which extends outward from the first plunger part 132. When a positive coil pulse is applied, the plunger assembly 130 will move towards the pole washer 150 (contacts closed). When a negative coil pulse is applied, the plunger assembly 130 will move towards the end cap 146 (contacts open) until the cap screw head 142 makes contact with the end cap 146 and defines a gap 166 between the second plunger part 134 and the end cap 146. The size of the gap 166 between the cap screw head 142 and the end cap 146 determines the force required to open the solenoid assembly 120 and also affects the coil current required to close the solenoid assembly 120.
During the closing operation, the coil assembly 122 and the magnet 138 work together to overcome the head spring 158 and the seal spring 156. Inversely, during the opening operation, the coil assembly 122 must cancel out the magnet 138 enough for the head spring 158 and the seal spring 156 to overcome the magnet 138.
The solenoid assembly 120 is secured inside the housing 102 with a solenoid retainer 168. An o-ring 170 is positioned between the end cap 146 and the solenoid retainer 168; however, this relationship is not visible in the cross-sectional view provided in
The PCB 172 is preferably located inside the housing 102 and below the solenoid assembly 120 as oriented in
The first stud-to-PCB terminal 174 and the second stud-to-PCB terminal (hidden) electrically connect the first stud 112 and the second stud 116 to the PCB 172, respectively. The first stud-to-PCB terminal 174 and the second stud-to-PCB terminal (hidden) are voltage sense lines linking the high current first and second studs 112, 116 to the PCB 172. Both the first stud-to-PCB terminal 174 and the second stud-to-PCB terminal (hidden) may comprise a bend 176 therein. The bend 176 allows for thermal expansion and contraction, without stressing the solder joint connecting the first stud-to-PCB terminal 174 and the second stud-To-PCB terminal (hidden) to the PCB 172.
The PCB 172 is also preferably electrically connected to the solenoid assembly 120 through the pair of coil terminals 126.
The location of the PCB 172 inside the housing 102 allows the PCB 172 to monitor battery voltage (batteries are connected to the high current studs 112, 116) without requiring any additional connections. Limiting the number of connections to the batteries 30, 40 also limits the opportunities for failure, short circuits, etc.
The housing 102 comprises a base 104 with a sealing lip 108 around a perimeter 106. A mounting plate gasket 186 is compressed between the sealing lip 108 and a mounting plate 182. The mounting plate 182 is preferably affixed to the housing 102 by rivets 188 and is of a thickness to provide adequate stiffness between the rivets 188. The mounting plate 182 may include machined counter bored recesses 184 for the rivets 188 to be recessed within.
Additionally or alternatively, any number of LED indicators 190 and lead wires for I/O ports (not shown) and the ground 192 may be connected to the PCB 172 inside the housing 102 but visible or accessible outside the housing 102, shown here in the base 104. For example, an LED 190 may signal whether the solenoid assembly 120 is closed by remaining “on-solid” and the LED 190 may be “on-blinking” when the solenoid assembly 120 is open. Additionally or alternatively, LEDs 190 may be used to signal other operational conditions and/or error message. Furthermore, additional leads (not shown) may be used for data transfer (e.g., updates or uploading operational data) or real-time system health monitoring. Multiple configurations of the contactor assembly 100 are possible. The prescribed number of lead wires (not shown) and/or LEDs 190 can be determined at the time of order and may be punched or drilled into the base 104 of the housing 102 at that time. Molded pockets 110 in the base 104 are preferably sized to accept standard cable seals 194 (see
In operation a microprocessor (not shown) on the PCB 172 will preferably be continuously monitoring voltage values of the main and auxiliary batteries 30, 40 and the current state of the solenoid assembly 120 (i.e., open or closed). The voltage values are preferably taken at the studs 112, 116. The voltage at the studs 112, 116 will differ from the voltage at each battery 30, 40 by a factor that is the product of current flow between batteries 30, 40 in amps multiplied by the resistance of the respective cable (not shown) connecting the batteries 30, 40 to their respective stud 112, 116. In all but the first minute or two after the contactor closes, the inter-battery current is normally of a magnitude such that the voltage drop across the cables connecting the batteries 30, 40 to the studs 112, 116 is not of great significance in determining the correct state for the solenoid assembly 120. To limit the need for a second “Vsense” connection at each battery 30, 40 and to avoid reacting to high cable voltage drop during the first seconds to minute or so after contactor operation, time delays are preferably introduced in the cycle of operation.
The ability to sense the independent voltages of the Main and Auxiliary batteries 30, 40 at the studs 112, 116 when the solenoid assembly 120 is open and millivolt difference between the Main and Auxiliary batteries 30, 40 at the studs 112, 116 when the solenoid assembly 120 is closed allows the microprocessor to use logic to verify if the solenoid assembly 120 is in the correct open or closed state. By nature, a bi-stable magnetic contactor does not require any power to stay in the contacts open or contacts closed state; the microprocessor provides a pulse of energy to actuate the solenoid assembly 10 and toggles the solenoid assembly 120 open or closed depending on voltage inputs measured at the studs 112, 116. The contactor assembly 100 is preferably designed to open and close the solenoid assembly 120 under specified maximum ambient and minimum voltage conditions. Without further intervention, permanent degradation of the magnet 138 could occur under certain anticipated combinations of voltage and temperature. To protect against this, the microprocessor (not shown) incorporates current limiting procedures.
It is possible that external influence such as shock or internal solenoid malfunction could create a situation in which the voltage values indicate to the microprocessor that the solenoid assembly 120 should be in one of an open or a closed state when in actuality the solenoid assembly 120 is in the opposite state. This failure will continue to cause unintended operation until corrected.
If the microprocessor determines the solenoid assembly 120 is in the incorrect state, the solenoid assembly 120 will be pulsed a predetermined number of times, preferably up to three times, in an attempt to restore the proper state. If the pulsing does not restore the solenoid assembly 120 to the proper state, the microprocessor will set an error condition. Once in the error condition the microprocessor will recheck the state of the solenoid assembly 120 at predetermined intervals, preferably about every two minutes.
It is preferable that the solenoid assembly 120 be open and remains open if the Main battery 30 is below a first voltage limit. If the solenoid assembly 120 is closed and voltage of the Main battery 30 falls below the first voltage limit, the solenoid assembly 120 is opened, given that other requirements are met, so that the loads on the auxiliary side of the system cannot draw down the Main battery 30.
The solenoid assembly 120 will be closed and remain closed if the voltage of the Main battery 30 is at or above a predetermined voltage limit sufficient to charge both batteries, barring the contactor assembly 100 experiencing any of the limitations set forth herein which would prevent the changing of state from open to closed.
Additionally or alternatively, instead of immediately toggling the solenoid assembly 120 “on” (contacts closed) and “off” (contacts open) upon reaching the contacts close voltage “VCON” and the contacts open voltage “VDCON” thresholds, the microprocessor will wait a predetermined duration of time (the duration of time could be set or changed according to operational demands and requirements.
If the measured Main battery voltage does not satisfy the requirements at any time during the “ON Delay/OFF Delay,” the time delay will restart. This ensures that the solenoid assembly 120 will not respond to transient conditions. For field diagnosis this means the appropriate VCON and VDCON voltage levels must be maintained constantly for a minimum of the predetermined “On Delay/OFF Delay” duration to induce a change of state.
There is a considerable lack of general understanding across the overall battery separator market as to what actually happens with respect to inrush current when two batteries at different potential are connected suddenly by an electromechanical device. The contacts 160 of the contactor assembly 100 are subject to a short duration but extremely high magnitude current spike that is only limited by the inherent impedance produced by the cable and other components in the circuit. Typical battery separators provide warnings that the device may be damaged at higher than rated operational voltages but do not provide safeguards to prevent this from happening. Higher than rated system voltage does not only risk damaging electronic components; these high voltage conditions may be passed through the logic and control circuit to the coil of the DC contactor where the coil windings and solenoid rare earth permanent magnet may be damaged. Higher than rated system voltages on only the Main battery stud 112 creates a greater potential differential between the Main and Auxiliary batteries studs 112, 116 that directly creates higher magnitude inrush currents that are likely to damage, weld, or prematurely age the contacts 160.
According to the present invention, the potential for damage from higher than rated system voltages may be reduced by continuously monitoring the voltage values at the studs 112, 116 and applying logic to determine if the system voltage has exceeded a predetermined upper limit programmed in the microprocessor (for example, 17 VDC). If voltage exceeds the predetermined limit on the Main battery stud 112 the contactor assembly 100 will remain in its current contacts open or contacts closed state and continue to monitor conditions until measurements indicate the voltage is within the predetermined limits. This circumstance will also set an error condition (for example, turning the LED 190 to “off-solid”) to notify the operator that there is a potentially hazardous system fault.
Similar to the High voltage lockout discussed above; low voltage measured at the Main battery stud 112 will create conditions that endanger proper operation of the contactor assembly 100 as well. Lower than rated system voltage may be passed through the logic and control circuit to the coil assembly 122 and the coil assembly 122 will not be given enough power to properly change the state of the solenoid assembly 122.
Lower than rated system voltage on only the Main battery stud 112 also likely indicates a damaged Main battery 30 and creates a greater potential differential between the Main and Auxiliary batteries 30, 40. The greater potential between batteries 30, 40 directly creates higher magnitude inrush currents that are likely to damage, weld, or prematurely age the contacts 160.
According to the present invention, the potential for damage from lower than rated system voltages may be reduced by continuously monitoring the Main and Auxiliary battery studs 112, 116 and applying logic to determine if the system voltage has dropped below a predetermined lower limit programmed in the microprocessor (for example, 9.8 VDC). If voltage is at or below the predetermined limit on the Main battery stud 112, the contactor assembly 100 will remain in its current contacts open or contacts closed state and continue to monitor conditions until measurements indicate the voltage is within the predetermined limits. This circumstance will set an error condition (for example, turning the LED 190 to “off-solid”) to notify the operator that there is a potentially hazardous system fault.
Additionally or alternatively, it is determined whether the voltage measurements require the opening or closing of the contactor 1016. If not, continue to monitor the voltage values 1018. If so, it is determined whether the voltages of the main and auxiliary battery are in a safe voltage range to open or close the contactor 1020. If the voltages are in the safe range, continue to monitor for a predetermined amount of time 1022. If the measurements remain consistent with switching the contactor, switch the state of the contactor 1024. If the voltages are not within the safe range, an error condition is set and monitoring continues 1026.
The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.
