Devices and methods for protection of rechargeable elements

In combination, a protection circuit and a chargeable element, comprising:

• a voltage regulator coupled in parallel to the chargeable element, the voltage regulator having a threshold ON voltage;
• and
• a variable resistor coupled in series to the chargeable element and electrically and thermally coupled to the voltage regulator,
• wherein the variable resistor limits current flowing through the voltage regulator during an overvoltage or overcurrent condition before the current reaches a level sufficient to cause the voltage regulator to fail.

A protection circuit for use with a chargeable element, comprising:

• a smart circuit;
• a variable current-limiting element coupled in series to the smart circuit;
• and
• a voltage regulator having first and second terminals for coupling to the chargeable element, the voltage regulator having a selected threshold ON voltage.

A protection system for use with a chargeable element, comprising:

• detection means for detecting an overcharging condition of the rechargeable element;
• shuntinng means, responsive to said detection means, for shunting the rechargeable element when the overcharging condition occurs;
• and
• protection means, responsive to the shunting means, for limiting current flowing in the rechargeable element when the shunting means shunts the rechargeable element.

A protection circuit for use with a charger and a chargeable element, comprising:

• a shunt regulator having first and second terminals for coupling in parallel across the chargeable element, the shunt regulator having a threshold ON voltage;
• a first positive temperature coefficient (PTC) device thermally and electrically coupled to the shunt regulator, the first PTC device having a first terminal for coupling to the charger in series and a second terminal for coupling to the chargeable element in series;
• and
• a second PTC device coupled in series with the shunt regulator,
• wherein the first PTC device switches from a relatively low resistance to a relatively high resistance when heated to a first transition temperature, and
• wherein the second PTC device switches from a relatively low resistance to a relatively high resistance when heated to a second transition temperature higher than the first transition temperature.

In combination, a protection circuit and a battery, the battery having a positive terminal and a negative terminal, the protection circuit comprising:

• a transistor switch coupled in series with the battery, such that, when the transistor switch in ON, the battery will discharge through a load;
• a temperature-dependent resistor thermally coupled to the transistor switch, and having first and second terminals, the first terminal coupled to the positive battery terminal;
• and
• a fixed resistor having a first terminal coupled to the second terminal fo the temperature dependent resistor, and a seond terminal coupled to the negative battery terminal, the respective temperature dependent resistor and fixed resistor thereby coupled in series with each other and in parallel with the battery,
• wherein the transistor switch has an activation gate coupled in a divider configuration to the second terminal of the temperature dependent resistor and first terminal of the fixed resistor.