Jose M. Fernandez

Overcharge current protection circuit and battery pack using same

A battery pack (62) comprises cells (74), and is charged by a charger (64) providing a current level. The charger (64) is a typical nickel-cadmium battery charger providing a first charge current level in excess of an optimum charge current level. The battery pack (62) further comprises a thermal sensing element (76) and an overcurrent charge protection circuit having an overcurrent switch (78), current sense circuit (80), comparator circuit (82), and temperature signal switch (84). If the current level through the cells (74) exceeds the optimum charge current level, the current sense circuit (80) provides a signal to comparator circuit (82) which actuates the temperature signal switch (84), simulating a hot battery pack. The charger (64) then switches to a second charge current level which does not exceed the optimum charge current level. If the charger (64) does not change current levels, a switch delay (86), after a brief period, accumulates enough voltage to actuate a driver switch (88) which opens the overcurrent switch (78), disconnecting the cells (74) from the charger (64).

Apparatus for simulating high battery temperature used in recharging lithium ion cells

A battery (200) includes a device (201) used for simulating a high temperature condition of a thermistor (216) located in battery (200). The battery (200) includes a charging node (203), temperature node (205) and ground node (207). A control circuit (209) is used with lithium ion cell (211) to measure voltage of lithium ion cell (211). Control circuit (209) produces a control signal when a desired voltage is reached during recharging. The control signal works with a high voltage switch (217), thermistor (216), diode (213) and resister (215) to control the voltage on temperature node (205). Any change in voltage on temperature node (205) may then be detected by an attached charging system to allow it to change its mode of operation.

Apparatus and method of simulating high battery temperature in a rechargeable battery

A device (111) for simulating a high battery temperature used in charging a rechargeable cell (101). The device takes advantage of a control signal generated by a voltage control circuit (103) used to disconnect a rechargeable cell (101) from a charging system (105) when a predetermined voltage is reached. The device (111) is generally used with cells having a lithium based chemistry and requiring a different charging regime then nickel chemistry cells. The device (111) is activated by the control signal from control circuit (103) which detects a predetermined voltage from rechargeable cell (101) enabling thermistor (113) to change its state. This change is detected by the charging system (105) which alters its mode of operation from a rapid charging rate to a slower charging rate. The device is retrofitable to existing rechargeable batteries allowing them to be charged using existing charging systems alien to the rechargeable battery.

Apparatus for controlling excess recharge current applied to a battery

A battery recharge current source 12 provides a recharge current 14 to battery cells 16. Recharge current 14 is in excess of an optimum recharge current level for battery cells 16 and is divided into currents 26 and 28 by variable shunt load 24 as controlled by charge current control circuit 18. Charge current control circuit 18 is comprised of current sense circuit 20 and load control circuit 22. Current sense circuit 20 produces a current sense signal in response to current through battery cells 16. Load control circuit 22 is responsive to the current sense signal and controls variable shunt load 24 as needed to conduct excess current away from the battery cells.