Chemistry: electrical current producing apparatus – product – and – With control means responsive to battery condition sensing...
Reexamination Certificate
2001-03-16
2003-09-09
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
With control means responsive to battery condition sensing...
C429S062000
Reexamination Certificate
active
06617069
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to batteries, which may be re-chargeable (“secondary”) batteries or non-rechargeable (“primary”) batteries, with over-discharge protection and devices for use in connection therewith.
2. Introduction of the Invention
The use of control circuitry outside the battery casing or cell, but within the housing of a battery pack containing two or more cells, is well-known, with separate integrated circuits, circuit boards, and discrete FETs employed to sense and control cell behavior. Over-discharge, sometimes referred to as “deep discharge”, means discharge of a battery to a level where irreversible damage occurs within the battery cell. This is undesirable, and U.S. Pat. Nos. 4,785,229 and 5,179,337, for example, describe various means for protecting rechargeable batteries from over-discharge by using protective circuits comprising field-effect transistors (FETs), for example a metal-oxide-silicon FET (MOSFET), coupled to conduct current from a re-chargeable battery to a load so long as the voltage potential across the battery is above the threshold which keeps the FET turned on. When the battery voltage drops below that threshold, the FET progressively turns off and reduces discharge to a negligible level, thus saving the battery from over-discharge.
SUMMARY OF THE INVENTION
The present invention relates to a much more convenient battery, which eliminates the need for separate coupling to an overdischarge protective device and, in one aspect, has a simple FET protection circuit, preferably mounted on a plastic substrate, which is housed within the battery cell itself. The invention is applicable both to primary and to secondary batteries. The invention accordingly provides a battery comprising positive and negative electrode materials in electrical contact with electrolyte material sealed within a casing (which may provide one of the electrode materials) provided with external positive and negative connection areas for electrical connection to load or other circuits when the battery is in use, wherein an over-discharge protection (ODP) circuit, preferably in the form of a semi-conductor device or integrated circuit, is provided within the casing and is electrically coupled between the electrode material and one of the said connection areas so as to substantially terminate discharge of the battery when the output voltage supplied by the battery falls below a predetermined level. The invention is useful with any battery which can be damaged by over-discharge, for example a nickel-cadmium battery or especially a lithium battery.
A preferred aspect of the present invention relates to a battery containing an over-discharge over-current preventing circuit, and more specifically relates to an over-discharge over-current preventing circuit composed of an over-discharge preventing circuit having a FET and an over-current protection element (PTC element) for protecting the FET, a primary or secondary battery having such an over-discharge over-current preventing circuit, and a battery pack comprising a plurality of primary or secondary batteries having such over-discharge over-current preventing circuits.
In this preferred aspect of the invention, consideration is also given to the problem of over-current when dealing with batteries. This is an effect wherein a battery will release excessive currents and generate heat when a short occurs in an electric circuit connected to the battery. Thus, it is necessary to protect the electrical circuits or batteries themselves from damage due to excessive currents and heat.
As devices for protecting electric circuits and the like from over-current, elements (PTC elements) having positive temperature coefficients composed of ceramics or preferably polymers are known. PTC elements composed of polymers (PPTC) are formed by dispersing particles of a conductive material inside a substrate composed of polymers, and while the electrical resistance of the device is extremely small while the current is less than or equal to a predetermined value, the electrical resistance will suddenly increase when the current exceeds the predetermined value, so as to substantially cut off the current. PPTCs are preferably such as to have the above-mentioned polymer layer sandwiched between two flat, parallel electrodes. For details on such devices, see U.S. Pat. Nos. 4,237,441, 4,238,812, 4,255,698, 4,426,633, and 5,801,612. Additionally, PPTCs can be obtained from Raychem Corporation under the product name “PolySwitch”.
Thus, in addition to a FET over-discharge preventing device, this preferred aspect of the invention advantageously includes protection against over-current, thus reducing the risk of the battery and/or the FET for protection against over-discharge being damaged by over-current if such an over-current phenomenon occurs. This combined OD and OC protection is especially advantageous when provided inside batteries or battery packs having a plurality of batteries, thus making replacement of damaged protective circuits difficult.
This aspect of the present invention was made in consideration of the above-described problems associated with the prior art, and has the object of offering a battery having an over-discharge over-current preventing circuit capable of retaining over-discharge protection capabilities even after the occurrence of an over-current phenomenon.
This aspect of the present invention has the further object of offering a battery pack having such an over-discharge over-current preventing circuit, and of offering such an over-discharge over-current preventing circuit.
In order to achieve the above purpose, a battery offered based on a first aspect of the present invention comprises (a) an electrolyte; (b) a positive electrode member and a negative electrode member in electrical contact with the electrolyte; (c) a pair of external connection terminals respectively connected electrically to corresponding electrode members; and (d) an over-discharge over-current preventing circuit comprising a FET and PTC element, the PTC element and a source electrode and drain electrode of the FET being serially connected between one of the electrode members and the corresponding external connection terminal, the gate electrode of the FET being connected to the other electrode member, the FET preventing over-discharge by stopping a supply of current to the external connection terminal when the voltage between the electrode members drops below a predetermined value, and the PTC element preventing over-current by restraining the supply of current to the external connection terminal when the current between the electrode members exceeds a predetermined value, thereby also protecting the FET from being damaged by an over-current.
Additionally, a battery pack offered based on a second aspect of the present invention comprises (a) a plurality of primary batteries comprising an electrolyte and a positive electrode member and a negative electrode member in electrical contact with the electrolyte; (b) a pair of external connection terminals respectively connected electrically to corresponding electrode members; and (c) an over-discharge over-current preventing circuit comprising a FET and PTC element, preferably within the battery pack, the PTC element and a source electrode and drain electrode of the FET being serially connected between one of the electrode members and the corresponding external connection terminal, the gate electrode of the FET being connected to the other electrode member, the FET preventing over-discharge by stopping a supply of current to the external connection terminal when the voltage between the electrode members drops below a predetermined value, and the PTC element preventing over-current by restraining the supply of current to the external connection terminal when the current between the electrode members exceeds a predetermined value, thereby also protecting the FET from being damaged by an over-current.
Furthermore, an over-discharge over-current preventing circuit offered
Furuta Masanori
Hopper George Frederick
Penneck Richard
Sato Takashi
Torii Shigefumi
LandOfFree
Battery over-discharge protection does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Battery over-discharge protection, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Battery over-discharge protection will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3096909