DETAILED ACTION
Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
Claim Objections
Claim 2 objected to because of the following informalities: the claim comprises a plurality of period signs which makes the claim multiple incomplete sentences. Appropriate correction is required.
Claim Rejections - 35 USC § 103
The following is a quotation of 35 U.S.C. 103 which forms the basis for all obviousness rejections set forth in this Office action:
A patent for a claimed invention may not be obtained, notwithstanding that the claimed invention is not identically disclosed as set forth in section 102, if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date of the claimed invention to a person having ordinary skill in the art to which the claimed invention pertains. Patentability shall not be negated by the manner in which the invention was made.
Claim(s) 1-22 are rejected under 35 U.S.C. 103 as being unpatentable over Onnerud et al. (US 2013/0278218) in view of Kim et al. (US 20180262021)
Re Claims 1 and 21; Onnerud discloses a method of battery balancing an electrical series string of lithium-ion batteries, the electrical series string of lithium-ion batteries including multiple lithium-ion batteries connected together in electrical series
Onnerud teaches a battery pack containing multiple lithium-ion cells arranged in series.
“A battery pack 150 comprises a number of cells, which may be arranged in a series…” (¶[0023]). This directly shows a series string of lithium-ion cells.
the multiple lithium-ion batteries each having a plurality of battery cells and a battery management system (BMS) comprising a comparator, (the voltage sensor 130 and the ADC+) a MOSFET, and a balancing resistor
Onnerud teaches a BMS with voltage monitoring, control electronics, MOSFET switches, and balancing resistors.
“The balancing circuit includes a resistor RB… and a transistor QB configured in parallel to a cell.” (¶[0027]).
“Voltage monitor 130 detects the voltage at the cells… forwards this information to the battery management system (BMS) controller 110.” (¶[0023]).
an ADC + microcontroller for voltage detection (¶[0024]).
while charging, detecting, using the comparator, when a battery voltage of each of the multiple lithium-ion batteries is near end-of-charge
Onnerud teaches detecting when a cell voltage exceeds a threshold during charging.
“The dissipative resistive element RB is switched… across any cell that exceeds a predetermined voltage threshold…” (¶[0004]). This threshold corresponds to “near end-of-charge.”
and upon detecting that the battery voltage of each of the multiple lithium-ion batteries is near end-of-charge, turning on the MOSFET of each respective one of the multiple lithium-ion batteries,
What Onnerud teaches:
Onnerud teaches turning on a MOSFET (switch transistor) to activate balancing when the voltage threshold is exceeded.
“The dissipative resistive element RB is switched using balancing switch transistor TsB across any cell that exceeds a predetermined voltage threshold…” (¶[0004]).
wherein turning on the MOSFET for a lithium-ion battery shunts a portion of charge current from the plurality of battery cells and through the balance resistor, which slows down charging of the lithium-ion battery.
What Onnerud teaches:
Onnerud teaches that activating the MOSFET bypasses charge current through the resistor and slows charging.
“Charge current to lower-capacity cells is being reduced…” (¶[0004]).
“The balancing circuit… can generate a balancing current IB… through the balancing circuit resistance RB.” (¶[0027]).
This is exactly the claimed “shunts a portion of charge current… which slows down charging.”
Series lithium-ion packs are universally charged using a single charger. Onnerud assumes a standard pack-level charger (¶[0002]–[0004]).
Onnerud does not disclose a single electrical charger explicitly stated.
However, using Kim teaches a single charger (12) for a series string (11a, b).
Therefore, it would have been obvious to one of the ordinary skilled in the art before the effective filing of the invention to have been motivated to use a single charger because:
A single charger ensures equal current through all series cells.
It simplifies system architecture.
It is the industry-standard configuration.
Thus, explicitly stating “single charger” does not confer patentable distinction.
Re Claims 2 and 22; Onnerud discloses a method of battery balancing an electrical series string of lithium-ion batteries, the electrical series string of lithium-ion batteries including multiple lithium-ion batteries connected together in electrical series
Onnerud teaches a battery pack containing multiple lithium-ion cells arranged in series.
“A battery pack 150 comprises a number of cells, which may be arranged in a series…” (¶[0023]).
the multiple lithium-ion batteries each having a plurality of battery cells and a battery management system (BMS) comprising an Analog-to-Digital Converter (ADC), a microcontroller, a MOSFET, and a balancing resistor
Onnerud explicitly discloses a BMS with an ADC, microcontroller, MOSFET, and balancing resistor.
“An analog-to-digital converter 116 converts the received voltage signals…” (¶[0024]).
“BMS microcontroller 118…” (¶[0024]).
“The balancing circuit includes a resistor RB… and a transistor QB configured in parallel to a cell.” (¶[0027]).
“The performance and lifetime of a battery pack is significantly affected… particularly in demanding applications such as operating electric vehicles.” (¶[0002]). Charging is inherent, but the number of chargers is not specified.
while charging, detecting, using the microcontroller and the Analog-to-Digital Converter (ADC), when a battery voltage of each of the multiple lithium-ion batteries is near end-of-charge;”
Onnerud teaches detecting cell voltage using an ADC and microcontroller.
“An analog-to-digital converter 116 converts the received voltage signals… for determining the voltage level at each of the battery cells 160A-N.” (¶[0024]).
“Based on the voltage data… the BMS controller 112 provides balancing control signals…” (¶[0024]).
Onnerud also teaches detecting when a cell reaches a high-voltage threshold:
“The dissipative resistive element RB is switched… across any cell that exceeds a predetermined voltage threshold…” (¶[0004]).
This corresponds to “near end-of-charge.”
and upon detecting that the battery voltage of each of the multiple lithium-ion batteries is near end-of-charge, turning on the MOSFET of each respective one of the multiple lithium-ion batteries,
Onnerud teaches turning on a MOSFET (switch transistor) to activate balancing when the voltage threshold is exceeded.
“The dissipative resistive element RB is switched using balancing switch transistor TsB across any cell that exceeds a predetermined voltage threshold…” (¶[0004]).
wherein turning on the MOSFET for a lithium-ion battery shunts a portion of charge current from the plurality of battery cells and through the balance resistor, slows down charging of the lithium-ion battery.
Onnerud teaches that activating the MOSFET bypasses charge current through the resistor and slows charging.
“Charge current to lower-capacity cells is being reduced…” (¶[0004]).
“The balancing circuit… can generate a balancing current IB… through the balancing circuit resistance RB.” (¶[0027]).
This is exactly the claimed “shunts a portion of charge current… which slows down charging.”
Onnerud does not disclose a single electrical charger explicitly stated.
However, using a single charger for a series string is standard practice
Series lithium-ion packs are universally charged using a single charger. Onnerud assumes a standard pack-level charger (¶[0002]–[0004]).
Therefore, it would have been obvious to one of the ordinary skilled in the art before the effective filing of the invention to have been motivated to use a single charger because:
A single charger ensures equal current through all series cells.
It simplifies system architecture.
It is the industry-standard configuration.
Thus, explicitly stating “single charger” does not confer patentable distinction.
Re Claim 3; Onnerud discloses wherein a battery voltage threshold where the balance resistor begins to bypass charge current is set to a voltage that is near the full charge voltage for the particular lithium-ion battery chemistry used.
Onnerud teaches that balancing is triggered when a cell approaches its upper-voltage limit, which corresponds to the full-charge voltage of the chemistry.
“The lifetime of the pack degrades significantly if the voltage across one or more of its component cells falls outside a predetermined range (typically 3 volts to 4.20 volts) during discharging or charging.” (¶[0002]).
“The dissipative resistive element RB is switched… across any cell that exceeds a predetermined voltage threshold…” (¶[0004]).
Re Claim 4; Onnerud discloses wherein as the electrical series string of batteries is charged, cell balancing will be turned on in each battery as it reaches the balance threshold, and eventually all of the batteries in the electrical series string will have cell balancing turned on. (Par 0023, 24)
Re Claim 5; Onnerud discloses, wherein balancing is performed only during charging. (Par 0034)
Re Claim 6; Onnerud discloses wherein the balancing requires the balancing circuit to detect when the battery is being charged. (Par 0024)
Re Claim 7; Onnerud discloses wherein the balancing is done by setting the voltage threshold for balancing to be near the full charge voltage, and when the battery is charging and reaches this threshold, balancing is enabled. (Fig. 9b)
Re Claim 8; Onnerud discloses wherein after charge termination, the battery voltage will naturally relax to a voltage below the threshold which disables balancing. (not shown but implicit)
Re Claim 9; Onnerud discloses wherein control electronics in the battery management system (BMS) provides a signal to the balancing circuit that indicates if the battery is being charged. (Fig. 5)
Re Claim 10; Onnerud discloses wherein balancing current isabalancing, which aims to keep cell voltages equal, and charging, which aims to bring the entire pack to a specific voltage or current threshold. Balancing current must be high enough to "bleed down" (in passive) or "transfer" (in active) energy from high-voltage cells faster than the charger pushes energy into them, but low enough that the charger's total current still tapers off, allowing it to detect the end of the charge cycle. High Enough to Effectively Balance Cells Preventing Premature Cutoff: When cells are unbalanced, the cell with the highest voltage (the "runner") reaches the overvoltage limit first. If the balancing current is too low, the BMS shuts down the entire charge prematurely, resulting in an partially charged pack).
Re Claim 11; Onnerud discloses wherein a value for balancing current.
Onnerud does not disclose is between 100mA and 500mA. It would have been obvious to one having ordinary skill in the art at the time the invention was made to have the value between 100mA and 500mA, since it has been held that discovering an optimum value of a result effective variable involves only routine skill in the art. In re Boesch, 617 F.2d 272, 205 USPQ 215 (CCPA 1980).
Re Claim 12; Onnerud discloses wherein a battery voltage threshold where the balance resistor begins to shunt charge current is set to a voltage that is near the full charge voltage for the particular lithium-ion battery chemistry used. (Fig. 9b)
Re Claim 13; Onnerud discloses as the electrical series string of batteries is charged, cell balancing will be turned on in each battery as it reaches the balance threshold, and eventually all of the batteries in the electrical series string will have cell balancing turned on. (Fig. 9b)
Re Claim 14; Onnerud discloses wherein balancing is performed only during charging. (Fig. 9b, Par 0034)
Re Claim 15; Onnerud discloses wherein the balancing requires the balancing circuit to detect when the battery is being charged. (Fig. 2b)
Re Claim 16; Onnerud discloses wherein the balancing is done by setting the voltage threshold for balancing to be near the full charge voltage, and when the battery is charging and reaches this threshold, balancing is enabled. (Fig. 9b)
Re Claim 17; Onnerud discloses wherein after charge termination, the battery voltage will naturally relax to a voltage below the threshold which disables balancing. (Not shown but implicit)
Re Claim 18; Onnerud discloses wherein control electronics in the battery management system (BMS) provides a signal to the balancing circuit that indicates if the battery is being charged. (Fig. 5)
Re Claim 19; Onnerud discloses, wherein balancing current ispack to a specific voltage or current threshold. Balancing current must be high enough to "bleed down" (in passive) or "transfer" (in active) energy from high-voltage cells faster than the charger pushes energy into them, but low enough that the charger's total current still tapers off, allowing it to detect the end of the charge cycle. High Enough to Effectively Balance Cells Preventing Premature Cutoff: When cells are unbalanced, the cell with the highest voltage (the "runner") reaches the overvoltage limit first. If the balancing current is too low, the BMS shuts down the entire charge prematurely, resulting in an partially charged pack).
Re Claim 20; Onnerud discloses wherein a value for balancing current.
Onnerud does not disclose is between 100mA and 500mA. It would have been obvious to one having ordinary skill in the art at the time the invention was made to have the value between 100mA and 500mA, since it has been held that discovering an optimum value of a result effective variable involves only routine skill in the art. In re Boesch, 617 F.2d 272, 205 USPQ 215 (CCPA 1980).
Response to Arguments
Applicant's arguments filed 05/21/2026 have been fully considered but they are not persuasive.
The applicant contends that Omerod fails to teach or suggest charging multiple lithium‑ion batteries using a single electrical charger and argues that the Examiner’s rationale lacks documentary support. This characterization is not accurate. The rejection does not rely on Omerod explicitly stating “single charger”; rather, it relies on the inherent and well‑established electrical behavior of series‑connected lithium‑ion cells. When cells are connected in series, the charging current is necessarily equal through all cells, and industry practice universally reflects this by using a single charger for the series string. This is not official notice, nor is it an unsupported generalization. It is a fundamental electrical reality recognized throughout battery‑system engineering. Omerod’s pack‑level balancing system presumes a charging environment for a series string, and whether the reference names the charger explicitly is immaterial to what it teaches. The applicant’s argument therefore does not rebut the core finding that Omerod teaches the charging configuration required by the claims.
Nevertheless, the Examiner has provided a reference (Kim US 20180262021 A1) solely based on the applicant’s argument.
The applicant also argues that Omerod does not disclose multiple batteries each having its own BMS performing MOSFET‑based shunting during charging. This argument attempts to distinguish the claims by describing a distributed, multi‑battery architecture, but the claims themselves do not require physically separate BMS units. They require only that each battery includes a MOSFET and balance resistor and that the BMS detects end‑of‑charge and activates the MOSFET to shunt current. Omerod teaches precisely this behavior: individual cell monitoring, individual cell balancing, MOSFET‑based shunting, and balancing triggered by cell‑voltage thresholds during charging. Whether Omerod’s controller is centralized or distributed is not a claimed limitation and cannot serve as a basis for patentability. The applicant’s argument relies on importing features from the specification into the claims, which is improper under MPEP § 2111.
The applicant further asserts that the Examiner’s rationale is conclusory and relies on hindsight. This is not the case. The rationale is grounded in Omerod’s explicit teachings and in well‑known engineering motivations, including ensuring uniform charging of series cells and using MOSFET‑based shunting to slow charging of high‑voltage cells. The rejection does not use the applicant’s disclosure as a roadmap; it relies solely on what Omerod teaches and what a person of ordinary skill would understand about series charging and balancing. The applicant has not identified any teaching in Omerod that would discourage the claimed method, nor have they provided evidence of unexpected results or criticality in the claimed sequence. As a result, the prima facie case remains intact.
Regarding the dependent claims reciting a balancing‑current range of 100–500 mA, the applicant argues that the Examiner has not shown balancing current to be a result‑effective variable. This argument is not persuasive. Omerod teaches MOSFET‑based shunting, balancing resistors, and balancing during charging. Balancing current is a result‑effective variable because it directly affects the rate at which charging is slowed, and it is controlled by resistor value and MOSFET conduction. Engineers routinely select balancing‑current values based on thermal limits, charge‑rate targets, and cell characteristics. The applicant has not demonstrated that the claimed range is critical, nor have they shown unexpected results or any teaching in the art that would discourage selecting this range. Under MPEP § 2144.05, optimizing a known variable through routine experimentation is obvious, and the rejection of claims 11 and 20 is therefore proper.
In summary, while the applicant provides a thorough narrative of their preferred architecture, the arguments do not identify any claim limitation missing from Omerod. They rely on distinctions not present in the claims, mischaracterize the teachings of the reference, and request documentary evidence for inherent electrical facts that do not require citation. The applicant has not shown criticality, unexpected results, or teaching away, and the Examiner’s rationale is fully supported by Omerod and by established engineering principles. For these reasons, the rejection under 35 U.S.C. § 103 is maintained.
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
Any inquiry concerning this communication or earlier communications from the examiner should be directed to DANIEL KESSIE whose telephone number is (571)272-4449. The examiner can normally be reached Monday-Friday 8am-5pmEst.
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If attempts to reach the examiner by telephone are unsuccessful, the examiner’s supervisor, Rexford Barnie can be reached at (571) 272-7492. The fax phone number for the organization where this application or proceeding is assigned is 571-273-8300.
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/DANIEL KESSIE/
07/07/2026
Primary Examiner, Art Unit 2836
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