Classifications

• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/007—Regulation of charging or discharging current or voltage
  • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
  • H02J7/00714—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery charging or discharging current
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
  • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
  • H02J7/007—Regulation of charging or discharging current or voltage
  • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
  • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage

Definitions

• the present invention relates to a method of regulating the charging of batteries containing a number of cells, for example NiCd cells, in that the battery is connected to a battery charger for impressing a current through the battery.
• a plurality of different principles for charging batteries containing, for example, NiCd cells are known in the art. Examples are constant current charging, constant voltage charging, pressure and temperature charging, and pulse charging.
• the major advantage afforded by constant current charging is that the charger may be of extremely simple design, while its major drawbacks are those of being re ⁇ stricted to a temperature range of between 0 and 40°C and an extremely long charging time at lower temperatures, since the permitted mean current under cold conditions is considerably lower than at room temperature.
• the charging itself takes place completely uncontrolled and without any adaptation whatever to the capacity of the cells to accept the charging energy.
• Constant voltage charging is also uncontrolled, but in this process the properties of the cell are utilized somewhat better, but also in this case the charging time will be long, in par ⁇ ticular at low temperatures.
• the task forming the basis of the present invention is to realize a novel method of regulating the charging of a battery containing a number of cells, for example NiCd cells, this method providing a complete charging of the battery in a considerably shorter time than has hitherto been possible at both room temperature and particularly at low temperatures.
• the primary advantage afforded by the method according to the present invention resides in the possibility of a com ⁇ plete charging of a battery in a considerably shorter time than has hitherto been possible, without any risk whatever of undesired pressure elevation in the individual cells arising from gas formation.
• a charger for carrying out the method according to the present invention may ap ⁇ pear to be relatively complex, its degree of complexity is undoubtedly motivated by the extraordinary advantages af ⁇ forded by the charger which gives as good as 50% shorter charging times, and in many cases even shorter, than prior art chargers, this without any risk whatever of undesired gas formation in the cells.
• the method ac ⁇ cording to the present invention makes it possible to take into account the capacity of the individual cells to re ⁇ ceive charging energy, whereby all cells in a battery will be given substantially the same charging level irrespec ⁇ tive of whether any of the cells become fully charged before any of the others.
• the method according to the present invention has proved to permit charging of batteries at such low temperatures as -20°C.
• the expression “rest vol ⁇ tage” is taken to signify the voltage measured at a given timepoint across the connection terminals of a battery, when no current flows to or from the battery.
• the expres ⁇ sion “terminal voltage” is taken to signify the voltage measured at a given timepoint across the connection ter ⁇ minals of the battery, when current is flowing to or from the battery.
• EMF EMF
• a battery which is to be charged according to the present invention may comprise, for example, ten NiCd cells each of 1.2V, which are connected in series to form a 12V bat ⁇ tery.
• An NiCd cell has a so-called critical voltage of 1.52-1.55V at room temperature. At or above this critical voltage, there is a risk of gas formation in the cell, and this critical voltage is established by purely chemical means. However, the value should not be considered as ab ⁇ solute, since it varies somewhat with the ambient temper ⁇ ature and, thereby, the temperature in the cell proper.
• a method for regu ⁇ lating the charging of the battery entails, as illus ⁇ trated more closely in the Drawing, that a number of re ⁇ latively short current pules 11, 12 and 13 are impressed through the battery.
• the value of the terminal voltage U1 , U2 and U3, respectively, achieved on each current pulse 11, 12, 13 is measured and the rest voltage U0 of the bat ⁇ tery is subtracted from the result, the obtained differ ⁇ ence being substantially equal to that voltage drop which occurs in total throughout the entire chain - cables, ter ⁇ minals, inner resistances of the battery, and so on - at the different values of the current pulses 11, 12 and 13.
• the value corresponding to the obtained voltage drop is stored in a suitable memory circuit, whereby there will be access to a direct value of the voltage drop occurring at each current value.
• the whole voltage value U1 , U2, U3, respectively can be stored instead of merely the difference between the above-mentioned voltage value and the rest voltage of the battery, whereafter the difference is calculated later.
• the Drawing shows the voltage along the* vertical axis and the time along the horizontal axis, the curve showing those voltage values which are attained at the different currents.
• the max ⁇ imum permitted terminal voltage of the battery without risk of gas formation in the cells will amount to 15.2- 15.5V.
• the battery can be impressed with a current 11 of the same value as the current pulse 11 at the time T1, and the cur- rent 11 is allowed to flow through the battery until the time T2, when the terminal voltage has reached the value U4, which corresponds to the maximum permitted terminal voltage plus the voltage drop measured at the short cur ⁇ rent pulse 11.
• the current is reduced to 12, whose value corresponds to the value of the short current pulse 12.
• This charging current 12 is maintained until the terminal voltage of the battery reaches the value U5 , which corresponds to the maximum permitted ter- minal voltage with the addition of the voltage drop estab ⁇ lished at the current pulse 12.
• the cur ⁇ rent 12 is reduced to the current 13, whereupon the cur ⁇ rent 13 is impressed through the battery until the maximum permitted terminal voltage plus the voltage drop at the short current pulse 13 is reached and corresponds to the terminal voltage U6.
• a criterium hereof may be that the value of the currents in 11, 12 and 13 once again in ⁇ crease instead of successively decreasing.
• the charging cycle proper or the method of charging, is largely a question of programming an apparatus according to Applicant's earlier patent application No. 8901317-1, a suitable apparatus being illustrated therein in Fig. 4.

Landscapes

• Engineering & Computer Science (AREA)
• Power Engineering (AREA)
• Secondary Cells (AREA)
• Charge And Discharge Circuits For Batteries Or The Like (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=20379602

Family Applications (1)

Country Status (6)

Cited By (5)

Families Citing this family (5)

Citations (3)

Family Cites Families (1)

• 1990
  • 1990-05-28 SE SE9001900A patent/SE468615B/sv not_active IP Right Cessation
• 1991
  • 1991-05-24 US US07/952,828 patent/US5329218A/en not_active Expired - Fee Related
  • 1991-05-24 AU AU79619/91A patent/AU7961991A/en not_active Abandoned
  • 1991-05-24 WO PCT/SE1991/000368 patent/WO1991019343A1/en active Application Filing
  • 1991-05-24 DE DE19914191204 patent/DE4191204T/de not_active Ceased
• 1992
  • 1992-11-09 GB GB9223474A patent/GB2260453B/en not_active Expired - Fee Related

Patent Citations (3)

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