Electricity: battery or capacitor charging or discharging – Cell or battery charger structure – For handheld device
Reexamination Certificate
1999-07-09
2001-01-30
Tso, Edward H. (Department: 2838)
Electricity: battery or capacitor charging or discharging
Cell or battery charger structure
For handheld device
Reexamination Certificate
active
06181105
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a self contained transportable power source maintenance and charge system for an implantable medical device encased in a sterile package. More specifically, the system includes a ribbon cable on a sterile plastic or blister package containing an implantable medical device. The system is connected to the ribbon cable, which in turn is coupled to the medical device, whereby a desired maintenance charge can be maintained on a battery of the medical device until the sterile package is opened for implanting the device.
Rechargeable lithium ion batteries are known for their high voltage and high energy density. Compared to nickel cadmium or nickel metal hydride batteries, lithium ion batteries contain 1.5 times more capacity, 3 times higher voltage with 1.5 to 2 times less weight. Unlike other rechargeable batteries, lithium ion batteries do not exhibit a memory effect, they are friendly to the environment and may be recharged in excess of 500 cycles while retaining acceptable capacity.
Another desirable feature of a lithium ion battery is that properly charged and discharged, lithium ion batteries do not produce gases; hence, they could be enclosed in a hermetically sealed enclosure.
With these attractive technical features in mind, lithium ion batteries may be utilized to power implantable devices.
Nevertheless, certain rechargeable lithium ion electrochemical cells and batteries require a specific voltage and or charge capacity control during storage or transit in order to preserve cell functional integrity. Due to cell chemistry, the cells exhibit a self discharge rate that may over time reduce the voltage down to a detrimental level. If the cell's voltage is allowed to discharge below a specific threshold voltage, prior to charging, the cell's ability to be recharged to the maximum specified capacity may be permanently lost. This loss of recharge capacity is usually referred to as faded capacity. Further, if the cell's voltage is allowed to drop to near zero volts, the cell's ability to be recharged at all may be permanently lost, rendering the cell useless. A known electrochemical mechanism that could cause irreversible damage to a lithium ion cell is dissolution of the current collector material upon voltage reduction below certain threshold.
Therefore, it becomes desirable to have a self contained transportable power source maintenance and charge system that can be pre-programmed to maintain a specific voltage and/or charge capacity of a power source, such as a lithium or any other rechargeable secondary power sources, that is affected by self discharge and its consequential damage.
2. Description of the Prior Art
Heretofore various battery power source charging systems have been proposed. Examples of some of these previously proposed systems are disclosed in the following U.S. patents:
U.S. Pat. No.
Patentee
5,411,537
Munshi et al.
5,631,537
Armstrong
5,670,862
Lewyn
5,675,235
Nagai
5,764,030
Gaza
5,811,959
Kejha
5,818,199
Beard
5,880,576
Nagai
SUMMARY OF THE INVENTION
The self contained transportable power source maintenance and charge system of the present invention uses an auxiliary power source and circuitry for delivering energy at a regulated voltage or capacity to a battery of a medical device to compensate for the inherent self discharge manifested by rechargeable power sources over storage or transit time.
The power source maintenance and charge system also provides a safe voltage or charge level for lithium ion cells and for devices that are powered by such a power source during storage or transit.
Further, the power source maintenance and charge system can safely switch from a maintenance mode to a charge mode by activating a Reed switch with a remote magnet or actuating a mechanical switch or other means thereby increasing the regulated maintenance voltage to a higher specified charging voltage. The charge activation using an electro-mechanical switch or Reed switch can be achieved inside a device's sterile blister package in order to prevent opening of the blister which may violate sterility. This feature also facilitates charging the device prior to implant without opening the sterile blister package.
REFERENCES:
patent: 4674509 (1987-06-01), Decote, Jr.
patent: 5811959 (1998-09-01), Kejha
Barreras, Sr. Francisco Jose
Cutolo Vincent
Echarri Guillermo
Echarri Roberto
Jimenez Oscar
Exonix Corporation
Tso Edward H.
Vigil Thomas R.
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