Electricity: battery or capacitor charging or discharging – Battery or cell discharging – With charging
Patent
1997-09-09
1999-08-24
Wong, Peter S.
Electricity: battery or capacitor charging or discharging
Battery or cell discharging
With charging
320DIG21, H02J 700
Patent
active
059428783
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to method and device for reducing memory effect of batteries mounted as a power source on, for example, an electric motor-operated vehicle.
TECHNICAL BACKGROUND
Batteries mounted as a power source on, for example, an electric motor-operated vehicle include the alkaine secondary battery or the like. When such batteries are used with repeated charge-discharge cycles without using up their battery capacity 100% (rated capacity), the discharge ends as shown in FIG. 3 within a period of time which is shorter than that of previous discharge. In the worst case, the battery voltage reaches a discharge end voltage before discharging almost no charge.
Such a phenomenon in which the discharge comes to an end in a shorter period of time than previously possible when the battery is used with repeated charge-discharge cycles without using up 100% of the battery capacity is known as the memory effect. To avoid such a situation, the battery capacity must be used up almost 100%. Practically the memory effect is reduced by discharging the battery at a relatively small current, for example 0.1 to 0.2 CA.
That is to say, a refresh discharge at a small current should be carried out when the discharge time (usable time of the battery) has become short. However, the decision on the timing when the refresh discharge should be carried out is up to general users and so it is not clear what timing is effective and efficient for reducing the memory effect. As a result, in most cases the refresh discharge is not effective.
The object of the invention made in view of the above is to provide method and device for reducing the memory effect of the battery by carrying out the refresh discharge at an appropriate timing either automatically or manually upon receiving an alarm to reduce the influence of the memory effect effectively and efficiently.
SUMMARY OF THE INVENTION
According to this method of the invention for reducing the memory effect of batteries, the discharge depth representing the ratio of discharged capacity relative to the rated discharge capacity of a battery is divided into a plurality of ranges with each range allocated with the number of charges at which a refresh discharge should be carried out. The discharge depth is obtained as a sum of discharged capacity between one charge and the next. At the time of charging, summing up the count of the number of charges in the corresponding range according to the discharge depth is repeated until the number of charges in any of the ranges reaches the number at which the refresh discharge should be carried out. Then the refresh discharge is carried out either automatically or manually. Since the discharge depth is divided into a plurality of ranges with each range allocated with the number of charges at which the refresh discharge should be carried out and the refresh discharge is carried out when the number of charges in any of the ranges reaches the allocated number, the refresh discharge is carried out at an appropriate timing at which the effect of the refresh discharge is most efficiently used either automatically or manually so that the influence of the memory effect is effectively and efficiently reduced.
Also, an alarm is given when the number of charges at which the refresh discharge should be carried out is reached. When the refresh discharge is carried out automatically, the alarm of carrying out the refresh discharge is to call the user's attention that the user's manner of carrying out the refresh discharge is inappropriate. When the refresh discharge is carried out manually, the manual operation is carried out upon an alarm of the refresh discharge.
The memory effect reducing device for storage batteries of the invention comprises; refresh discharge setting means for dividing the discharge depth representing the ratio of discharged capacity relative to the rated capacity of the storage battery into a plurality of ranges and allocating the number of charges to each of the ranges at which number the refresh discharge should
REFERENCES:
patent: 5561362 (1996-10-01), Kawamura et al.
patent: 5650712 (1997-07-01), Kawai et al.
patent: 5717256 (1998-02-01), Okumura et al.
Luk Lawrence
Wong Peter S.
Yamaha Hatsudoki Kabushiki Kaisha
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