Intelligent serial battery charger and charging block

Abstract

A serial battery charger including a number of serially connected battery charging sections in which the battery charging section is characterized by a first and second parallelly connected branches. The first branch includes terminals for connecting to the battery to be charged and a current blocking device and the second branch includes a by-passing switch which shunts across the terminals of the first branch when activated. The blocking device in the first branch prevents adverse reverse current flow from the battery to the charger when there is no power supply and also functions as a current block to prevent adverse flow of current from the battery into the shunting by-passing switch when the power supply to the charging section is in operation. This invention provides a simple solution to fulfil the conflicting requirements of an intelligent serial battery charger.

Description

[0001]This application claims priority under 35 U.S.C. §§119 and / or 365 to 01106195.9 filed in Hong Kong on Sep. 3, 2001; the entire content of which is hereby incorporated by reference.FIELD OF THE INVENTION[0002]The present invention relates to battery chargers for charging a plurality of rechargeable batteries connected in series. More particularly, this invention relates to battery chargers having a plurality of serially connected battery charging sections. More specifically, although not solely limiting thereto, this invention relates to serial battery chargers in which a battery in any one of the serially connected charging sections can be removed or bypassed without materially affecting the charging conditions of the batteries remaining in other charging sections of the serial battery charger. Furthermore, this invention relates to serial battery chargers in which there is utilized a simple electronic element which provides a low-impedance to the charging circuit during charg...

AI Technical Summary

Benefits of technology

[0011]It is therefore an object of the present invention to obviate the problems or shortcomings associated with existing or known serial battery chargers. In particular, it is an object of the present invention to provide a circuit arrangement for an improved battery charging section which can be used in serial chargers so that the charging section can be shunted or by-passed when selected and, at the same time, providing blocking means to prevent reverse current.

[0012]An important objective of the present invention is therefore to provide an intelligent serial battery chargers in which the charging current or charging conditions of one battery in the serial connection is largely unaffected by the charging conditions of other batteries in the serial connection.

[0013]An equally important object of the present invention is to provide a serial battery charger in which a battery can be removed from the serially connected battery at any time without disrupting the charging of other batteries and, at the same time, adverse reverse current flow from a battery can be avoided.

Problems solved by technology

When a battery is being charged, it will produce oxygen on the electrode and the consumption of oxygen by the negative electrode will cause the battery to heat up.

This is because if the batteries are fast charged in parallel, a power supply having a very large current supply rating will be required and this may be very costly.

This may also create great difficulty in a lot of circumstances.

For example, when a battery is removed from the charger upon completion of charging to avoid overheating or damaging or because it is already defective, charging will be disrupted until a replacement battery has been inserted into the charger.

Similar problems also arise if rechargeable batteries of different capacities are charged together or good batteries are mixed with bad ones.

This is because when a battery of a smaller capacity has been fully charged, there is a good chance that a battery of a larger capacity still requires charging.

As a result, overheating, battery damage or even explosion may result.

This is obviously undesirable as the remaining batteries may still require further charging.

Furthermore, whenever batteries are inserted or removed from a serial battery charger during the charging process, the whole charging process will be interrupted.

For many battery chargers, it is known that, when power supply to the battery charger is turned off, there may be a reverse leakage current which flows from the battery to the charger or the peripheral circuitry.

Reverse leakage current among the serially connected batteries could also cause reverse charging of individual batteries by other batteries that are connected in the series charger.

This is clearly undesirable which may cause draining of the full battery capacity and may even damage the charger.

While serial chargers having arrangements to by-pass some or all of the charging sections have been known, they are generally very complicated and do not simultaneously include means or circuits to prevent reverse leakage or discharge from the batteries.

To provide a serial battery charger which fulfils the above requirements is a difficult task because several conflicting requirements need to be met.

Secondly, that serial block device must have a low impedance when there is a forward current which flows into the battery for battery charging.

On the other hand, if the blocking device has a low forward impedance when the by-passing switch has been activated (which usually occurs when there is still power supply to the battery charging terminals), that low-impedance blocking device will compete with the by-passing switch for the supplied current and, as a result, adverse charging current will keep flowing into the batteries.

In addition, that blocking device must have a high impedance when the by-passing switch has been activated, otherwise, a large and un-desirable current will flow in a current loop which is formed by the battery, the blocking device and the by-passing switch.

Images