GB2359945A - Control of battery charging - Google Patents

Description

1 PROCESS FOR CONTROLLING BATTERY RECHARGING AND DEVICE FOR THE

IMPLEMENTATION OF THE PROCESS.

2359945 The present Invention relates to the recharging of a battery, in particular that of a radiotelephony handset. In order to limit the weight of the, handset;. the use. of lead batterleis i's avQided and preference given for example to. batteries employing Cadmium-Nick-o4 or N1MH (Nickel Metal Hydridia) technologies., althouWb the are more delicate.. In order to avoid damagn y them, they are recharged using a limited cuirent, 'from a charger comprising. a current generator.

A current generator isi by natuze, designed to, deliver the re4uisi.?-.e currpnt, regardless of the..

voltage of the battery, Hence, a momentarily very; low.

battery voltage.'cannot cause an excessive::;nrush current. However, the voltage of the batttry, Which rises owing to the recharging current, cannot oppose this current when' the battery is recharged.: The energy of the recharging currentl which is normally converted Into chemical energy for rechargng the batteiry, can do longer perform this conversion when all the electrolyte has been converted and the battery Is e.quivalent, in. respect of the. recharging. current, to a heating resistor. The corresponding heating might thereford'' destroy it if it is not possible to detect the end 6f' chemical recharging state,,.so as to stop the recharging. current.

To detect the end of. rechargingf it is known practice to monitor the voltage of the battery, 'which increases during recharging but decreases slightly and temporarily in the transient phase during which, at the', end of recharging, the battery begins to become--equivalent to a heating resistor.' However, in an environment of use in an' apparatus, such as the atotementioned haMset, the circuits supplied by the battery are sometimes placed.

temporarily on standby and reactivated, so. that the,' variations in discharge current induced thereby cause positive or negative j umpa. j fi battery voltagis.

r Recharging might therefore be interrupted too soon c.', conversely, it ra. ght never be interrupted. if such a 1 1 voltage jump masks the temporary tall In voltage, indicative of the end of redbarging..

The applicant has contemplated monztori.ng, addition to. the voltage, the absolute le-Vel of the temperature of the battery so as to:detect the changeover to the-"heating resistorll.mode. However, the discharge current, or else the environmental conditipn;o:',.

of the terminal, such as exposure to the '.sun 1 s raysf may also cause heating of: the battery, which might wrongly be regarded.as an end of recharging, The present invention aims to reliably and: effectively control the recharging of a batthry.

Accordingly, the invention firstly relates to a process for controlling. the recharging of. a battery.

from a generator, in which p.roCesa:' - the battery is charged. alternately and cyclically based on curr ent:n d on voltage, - during,the voltage-based charging.cycles, the charging voltage is allowed to vary andi beyond a bottom threshold, it Is allowed to vary beyond a top threshold fo ' r a predetermined. duration before allowing it to fall back to..the. bottom threshold, - during the current-based charging the, i value of the charging current is varied cyclically frofn'.'.. 25 an Initial value, - the temperature of the battery is monitored.... so as to sea.rch for and meagure therein a cQrr6sponding...: variation of the temperature'. and - the value of the current is reduiced if the..

temperature variation exceeds a target threshold.

Thus.. at the start of charging, and up to the: bottom threshold of charging voltage, the Pharging of' the battery is accelerated: by performing a voltag'ebased charging in the time intervals sepaxating the time intervals duxing which the current-based charging, is performed.

However, throughoutthe charging, the variati6nl in current is equivalent to a succession of pulat-$".: which is manifested thermally at the. battery,level by,'S''., succession of thermal cycles in phase with these pulses. It is this sensiltivity of conversion', or slop!'(. between the variation in current and variation temperature which. is thug determined so as, if need b',,, to bring,the current to a value such that it does no;,:

by itself,, heat the battery by a value: exceeding the target threshold value. -The. value of the ambient temperature does not interveno as such, snce.it may be constant, and sin.ce It Is sufficlett to dedijct It frow the temperature rdeasurements so as to deduce therefr.'m the thermal variation, or since it may drift but It is' equivalent to avariable changing at a dif f erdn't frequency from that of the pulsesi, hence.with h6 phase relationship with. the:pulses,: this making it possiblor eventually, to accurately determine their influence. It is appreciated that the process applies to any b,attex:y' be it isolated or incorporated into any type of apparatus.

Preferably, the value of the temperature 20 variation is slaved to the threshold value)y adjustin.g is the current in accordance with the deviation between the said temperature values.

It is thus possible. to recharge to. the.maximum. current compatible with. the target value.

Advantageously, the value of the temperature, variation is determined by comparison between.a heatin9 slope.and a cooling slope.

It. 1.s thus possible to circumvent the drifting of the ambient without having to monitor 'the latter....

since its. overall effect is th.."en zero.

In a particular implementation, the battery is... recharged from a current generator and from a voltage generator.

In another, preferred', impleMentation the battery is recharg.ed from a current gdnexator and from, a voltage-based slaving 'by' means of. the. current' generator.

In this case. the adding of further hardware is:: limited.

The invention furthermord. relates to a device.:: for controlling recharging of a;battery configured'' as to be supplied.by a gen.eratoi:f. compriising,,.

- means of. variation for the rechatgin:g current, - sequencer ineans for cyclically the means of variation, means for providing a cha.t.g:lt)g voltagei means for measuring the'devi. ation:between tho : 1 p charging voltage of the battery and bottbm and:to thresholds of charging voltage, means of measuring the tiamperatiire of the; battery, means of providing a ta:tg6t threishold vi.;(..luf 15 for temperature mbdulation of the,ba.ttery, - means of calculation, lin.ked at input to:the and to 'the measuring means so as to d#termino temperature varia:ton value and:.to c;oh'trol incans:.of a threshold-providinc meanj temperaturetherefrom.

adjusting the current in accordance with the deviat.io-pl between the temperature variat.idn Value and t hie threshold value, 'az well as( iinOr. the action of the means for measuring the temperatur,-. deviation:. to control the means'-df providing the.cha.kgl'ng.oltage.

The device can comprise a.current ge'nerator 'and a voltage generator.

Preferably.. the Ice gomp;rises a current generator and a vo Itage-based by moons of the current generator.

The inventi. on will. be bttter.r! understood with the aid of the..following deocript.loo of a' p ref erred mode of Implementation of the process bf the' Invention., with reference to.the appended d.r4wi..ngin which:

- Figure 1. is a functional. bliock diagram of a radiotelephony handset implementing the process of the invention, - Figure 2 is a time chart illts'trating a thermal excitation o the battery of the handset, t Figure 3 is a chart illustrating the steps of the processf - Figure 4 is a time chart illustratizig. the principle of alternate charging, based on voltage And 5 on current, of the battery, - Figures 5A and 5B forming Figure 5 respectively illustrate, as a function of the time. t'dl the slaving of the charging voltage of the battery', and' - Figure 6 is a flowchart illustrating the slaving process of the invention...

The radiotelephony handset represented. in Figure 1 comprises a battery 2, here of the. NiMM type' ' in series with a breaker 3, presented in the forM of a relay, for controlling the recharging. current o f t he battery 2, originating from a generator 1, here a current generatorr s. upplied from the mains and wh,idh can be plugged into the'handset via a connector.

In the present patent appli. cation, the problem of the charging of the battery.2 is dealt with recharging being the most frequent _specific case. The concepts of charging and of recharging are regard.id bore as being strictly identical.

Fixed on the battery 2 is a temperato.xe detector 4 and. here specifically, a resistor, 0 r thermistor, of value varying with temperature acc ording to a known law.. As a variant, it would be possible.'..to provide a diode,, whose voltage drop, and hence 'whos.e static and dynamic resistance, varies in the oppb.s.ite direction to the temperature. 30 A central unit with microprocessor 11, wit h operation clocked by a timebase 10, controls thd recharging of battery 2, by operating the relay 3. For the charging and recharing of the battOry 2, the handset essentially comprises two sets of circuits:

- a set of circuits 4 and 12 to 21, for current-based recharging, and - a set of circuits 22 to 25, for voltagebased recharging.

-. 6 - As mentioned at the. start, curren.t.-basgd charging consists' in providing the battery. 2 with current independent of the voltaige which it exhibitp. whereas voltage-based charging consists In providin'. the battery 2 with a current determined bt thic'. deviation between the voltage of a source,, determined' value,: and the voltage, increas.ing, of the battery 2.

These two sets are successi.vely hereinbelow.

The central unit comprises at input an analogue/digital b.onverter (A DC). 12: measuring the valut of the resistor 4:' for example,by.measuring its voltagt when it is supplied with a determined current. The output of the ADC.12 Is liniced to the positive input. o:ú a subtractor 16 Peceiving, on its negative input, th.C. output of an adder I.S. The adder.15 receives the au.tput o.t a memory 13 providing an ambient temperature va.lue, described:.

(def ined later) and the output.of a. memory. 14 providing:...,.target threshold Tc, a value of a limiting temperature modultion of the battery 2 by the current..

from the aenerator 1.

The result output by the subtractor 16 Integrated in an Integrat,Qx 17:, tte. result of which is routed, by a router 19, represented ve ry diagrammat i call y 'by a relay J01adek to a calculating.

block 20 or to a calculating bloc.k 21. depending on the j control of the router 19, originating from a sequencer circuit 18.

The calcu,.lating block. 20' calculates the value of the ambient tenperature and. stores it in memory 13.. The expression ambient 'teTperature is understood to mean the temperat. ure of the battety.2 in the.absence. 0.t recharging curren.t. The ambient temp6rature theref ore depends in particular on the tdinperature of the ambient air, on the temptrature of any surface on which the handset is placed, on its direct exposure to the sun rays and also on the discharge current in the telephone i components, or ijsdful chrge, of the. handset, whi6h not represented.

The calculating block 21 -cod.trolso in... accordance with the 6utput f rom the integrator.17,. 5 breaker, 3 so as to limit 'the mean 'rechar 'ing curr 9 a value such that by: itself. it only causes.. heAting p t:. the battery 2 riot. exOcedi.ng, the threshold value.,.T.c. of;".. the memory 14 (or a valve tied to the latt.er, Isuch:is. proportional), an.d does.:.so ihd.ependently of the other causes of heating. It, is. therefore. necessary to'be able..! to discriminate between the heating from 'the recharging current and that due to the other dause!p indicated above.

As indicated,. th. c handset compriset a: Stt of circuits 22 to 25 for the voltage-based'. reCh.ar4ihg 6f the 'battery 2. It comprisea an anal6gue/di'gital converter 24 linked at input to the terminals. of the..:

battery 2 (the earth connection2. 1 Inked tQ, the e.otive, terminal of the biattery: 2 hav!s r)..ot been rieprdaRrte.d) and a memory 23 containing two numbers representirig two values of threshold VOltge. respectively top, V1., and bottom, VO, for rechargino the'battery 2.

The circuits 23 and 24 are respectively linked the.'..- at each output to a subtraction input.and to addition Input of a subtractor 25 whose outppt covitrols a calculating block 22 which itself co"nt.rdls. the breaker 3 via a circuit. 26, a two-input OR gate, also controlled.by the calculating block 21.

Figure 2:the principle' Of the current-based charging of the process of the inventi.on by means of the tirst set of circuits 4 and 12 to:. 2 1.0 the temperature of the battery 2 measured (.12) be.ifig plotted as ordinat4 and the t'.j.Th t as'abscisjia, Curve CO represelts the, profile of the am.b'l.ejht temperature, of the battery 2, as defined heretnabove. This temperature increases 'here according td monotonic curve CO-with-sijbstantially constant slope.

Curve Cl represiznts the temperature of the ' battery 2 actually rneasur"0d, tht is to.9,by the:arnblent'.

i temperature (C0). to. which is added a positive modulation or variatibn due to the fact that thi$' recharging current - varies frpm.an Initial. valuei, whii,Ic. being applied cyplically, according to duccessl'!ve':

periods T, to thi3 battery 2 each 'time for a cha.r'gi::ng, duration tc follcvwed by a stoppage of duration ta.,: T.he' battery 2 therefore receives cyclic current pul s es:a t' determined Instants.

In this example, tC - 10 min.

ta = 5 mih'.

With respect to the ambient CO, the initi.,'al.' temperature 00 (here at a given instant with th& thermal regime already established.) vatiest over tie.' duration tc of th.e first phase (curve C2), und.er thd, effect of the heating due to the recha.rgin'g curren.t, towards a top as.ym'ptot.ic, value parallel to. the, curive:

CO. The heating perceived, w. hich will control. the' regulation. is strictly speaking the difference betwe'onl the heating due to the. currebt and the natural codlip during this phaso. tc. The temperature variation. is' 6f exponential form,. dwindling away as one approaches theasymptote. Added thereto, as absolute variation,.is the drift. positive as here or else negativel, of the ambient temperature col going from 0 (arbitraJcy. reference) to 0A1.

During the -second phase ta of rest (curve. C3l: the thermal excitatioti of the battery 2 by, the recharging current no longer exists ond curve C3. N1.5" the "natural" curve CO of the ambient as bottom asymptote. Curve C3 may therefore rise, If curve Cd.: rises sufficiently, or else, in the general. icaa'e represented here,.. it falls back to a value 02t t be..'; ambient temperatute having then reached the.val.ue.,.OA,.

The sawtooth shape of the curves.C2, C3 is repeated for. the subsequent periods T.

As a first approximation, the ainbieii.t temperature CO may be regarded, for the ca.ke. of' - expl-anation, as varying with -a. time constant which is.' 1 much greater than the period T, that is to say. the. curve CO is substantially a string of straight Un6, segments, ea.ch period T corresponding to a Oegment." Th4. period T/ here 15 minutes, is however large enough,: here of the order of magnitude of the thermal -time; constant of the battery 2, f or the thermal. modulat.9n to be clearly discernible and hence measUrable. with good accuracy. More generally, since the profile of the ambient CO does not exh;ibit any correlation with: thie'.

controlled thermal modulation, the ambient iterely introduces background noise' into the calculatIoner which is filtered by repeating, or integrating, thei-i2: results.

Curve C4, the mean or integral of cUrves C 2.. an d':' C3, circumvents the instantaneous effects oú1 the pa 5 tc and ta and is parallel, 'when the recjula,ting of current is at equilibriumi, to the ambient aurve C.0 and: above, by A@. The temperature offset A9 between cirv- c. CO and C4 therefore corresponds. to an 'equilib.riid.

between the therthal excitation due to the cutrent, during tc, and the llde-excitationll due to the ambiei.it,,. which then progressively, Rbsorbs the thermal overrun o'f". the battery 2, during ta. The larger the c(eviation the more effective is this shift back towards the curve:

CO (slope of the exponential for the decrease, In. deviation). It is therefore possi:ble to C-Stimate Ae.; according to the ensuing cooling effect which is equalf. in absolute value and at equilibriumt to the thermal.' heating produced by the recharging current:. 1 when it flows, that is to say here according to..a relativd.. angle of flow P.

Here: P L T with L: relative angle of flow of the current n a circuit 38 (Fig. 3) for adjusting. the width. of cyclic.,. pulses of the recharging current, here havihg a pcriod':. of much less than T,' adjusting..the re'qg.isite mean current so as not to exceed the heating threshold.

i t.:.

The thermal excitation 'Power RI2 P (R battetyl;." resistance), or thermal heating flux#'; is. equal to the;: thermal cooling flux, proportional.:to 40. Thus, at,. equilibrium, the heating 40 represents. the 'Value of the' resistance R. Stated otherwise, the integral of the thermal! flux. due to the current durng. t..c:is to integral of the coolin during ta.

We may therefore write:

Aoc - 01 - 00 - ECH +.OA1 and A0a = 02 - 01 RAP + (OAI ta.te).

since OAI/to (OA2 -.OAI) 't4o with:

ECH: heating due to the recharoing:current, and RAP: thermal shift back toward. ambient, dutirig.':::

in this example, different du;oatibne ta cind tc;':

have been chosen. The effects of the'; drifting of the::,!' ambient CO will however be circumvented. The ambient CO, assumed to vary substaLntially Iinearlyk theregore'.' has, in the two phases tc and ta,, a' temperature drift..:

effect proportional to. the relevant: duration tc or ta.

Knowing the ratio of these two durations tc and ta,. it! is possible to correct the tempera-ure me.asurementg;:. so:.

as to circumvent the drifting. of: - the' ambient CO, b norming the temperature variations.:With respect to.:' time:

Age A0a te ta (5) so as ultimately to determine a thermal gradient Per:.! unit time, by means of a single temp!Prature sensor (4) Stated otherwise, the natutial, cooling of 'the..'!;. battery 2, proportional to tho. mdan heating AO( compensates for the introduction' o:f th41rMal ener,

9y - This introduction of thermal energy is proportional to.:!: the thermal conversion slope, or effectiveness, of the.: recharging current,. to the square.of' the value 1. of this current and to the shape factors'. tc/T and L. The

1 1.

11 - values I, tc/T and L being known, A0c ir, therefore directly indicative of the tharmal sensitivity, or conversion slope... of the battery '2 with respect to the recharging current.

It is then possible to establish an estimate EST of the amplitude of 'the thermal modulation of the battery 2 througrh the mpdulation..of the current., EST representing AG toi within a factor (x. Starting from equation (5.) and. expanding according to equations (2.) and (3), at equil:ibrium, When ECH -RA..P, we obtain:. W EST Ak- 40a ECH + 9Al[-ECH+.9AIL01 ta ta tC tC - ECH (I± :ta, with.

1 (6).

k (OC/A): thermal.'sensitivity of the battery and a = 1. + c 3 here. ta As shown by the 'structure of the term (%,'the estimate or fictitious:heating ST is a calculated value which is proportional to the. 'actual heating value.

40 and represerns it perfectly. It is. therefore. sufficient to s14ve the variable EST to. a beating threshold value -so as likewise to slave the actual heating 40 to a corresponding threshold value Tc.

The recharging current I is provided by the current generatoz.1, adjuctment; of the in.stantanoput. current of which is not envisaged in this example. AS a' variant; it would. have been possible to envisage static regulation by means of a..cieries'element with'adjustable impedance, such as a transistor, without cutting off, the current. Here however, in order to adjust the mea"n current during the phases tc, the current is cut of f cyclically in the circuit 38 so as to allow. it through in pulses only during the fraction L of the time. (relative angle of flow). Since the pulsatile current is equivalent to a direct curren't. (mean current) on which is superimposed an alternating component, the..

latter can be. eliminated, as therefore can the additional heating which it induces, by tiltering it through a reactive element downstream of the breaker 3, such as for example a series inductor.

Figure 3 illue.trates the process for regulating current-based chArging as explained hereinabove with reference to Figure 2.

The temperature of the battery 2 being monitored and recorded continuously, or cyclically, by the sensor 4 in a step 32, the foilowing is calculated at a step 33:

EST - A0c 40a te/ta which, as indicated previously, amounts to comparin(l (subtracting) the beating slope 40c/tc and the cooling' slope A0a/ta. In this example, the deviation in the slopes is brought into the teTperature: domainby multiplying by a certain duration,. here taken to tc. In another example, the threshold 34 could howeve r have been expressed in the form of a thermal slope with.

respect to time. This value. EST i.g compared (subtracted), in & step 35., with a threshol,d value Tc originating from a memory 34 (equivalent of'. the memory. 14). The differende obtained is' amplified by. a factor G. in a step 36 so as to provide a utilizable error signal, e which is integrated 'in a step 37, over a sliding. duration of around T, so as to provide an integrated error signal INT which controls. the adjusting of the.. gate 38, that is to say fixes the shape factor L, or.: percentage of time of flow,. and hence the mean current..

The output from the gate 38 1.9 applied to an input Ofthe gate 40, another input of which receives (stop 39). a fixed shape factor signal tc/T (here 213)' originating. from the sequencer 18 so as to switch oft thb breaker.3 during ta. Through the OR gate 26, the output front the. gate 40 controls the breaker 3 and hence the inean. recharging current I. L during the phase tc.

A loop for regulating the rise in the temperature of the battery 2 is thus Constructed, circumventing the variations in the ambient.

If the formula serving to estimate t.h.e temperature rise were otherwise. and exhibited some sensitivity to the drifting of the ambient, it would be possible to envisage measuring the latter cyclically, by stopping all excitation (to) for one or more periodh T, so as to revert substantially and temporarily to the curve CO. In practice, thi.s cat. be achieved, In the example detailed, by teinporarily' forcing the target value Tc to zero (14; 34).

To likewise detect an abrupt drift in the ambient temperature, the calculating block 21 could be designed to include a comparator. for comparing, with aT. alarm threshold, the aeviation (c or INT) between the measured temperature modulation an O.the targict vilue Ti and for controlling an ambient temperature measurement,. cycle if the devic.ition.,exceeds the..threshold.' By virtue of the above. ot s of the process of.

ap the invention, it is t. hus possible to reduc6 the value. of the current (reduction in the shape factor. F.) if the temperature modulaltion. exceeds the'.target threshold Tc.'.

Preferably, the value of the temperature. modulation is slaved, as explained, to the threshold value Tot so that the current holds a maximum valuer. allowing rapid r.echarging, but temaining 'compatible with the temperature rIse threshold To. The shape factor F may therefore also inctease temporarily', if. for example the telephone cirduits of the terminal' discharge the battery 2.

Current-based charging 'having hus been described, - all ' the steps of the process of the invention, which. utilize:s such current-based chargino and voltage-based 'charging, will 1 now be described According. to this proceiss.Ifor controlling the recharging of the battery 2 from the generator.l:

- the battery 2 is charged alternately and cyclically based on current and on voltage, - during the voltage-based charging cycleaf.the charging voltage is allowed to vary and, beyond the bottom threshold VOi it is allowed,'to vary beyond the i 14 - top threshold V1 for a predetermined duration Ts before. allowing it to fall back to the bottom threshold VO, the temperature of the battery 2 is monitored so as.to:. search for and measure therein a corresponding. 5 variation of the temperature, - during the current-based charging cycle.s, the:. value of the charging current is varied cyclically from. an initial value, and - the value of the current is reduced if the temperature variation exceeds a target threshold TC More precisely, the voltage-based chargingisi perf.ormed during the period of duration ta of Figure 2, which was specified as being a period with zero recharging current. The sequencer circuit 18 controla the above alternation, by alternately enabling the,:

outputs of the calculating blocks 21 and 22. The voltage-based re. charging is perfornied by the circuits 22 to 25 and the battery 2 is then:: rechargtd from the current generator 1 and from a voltage-based slaving by means.of the latter.and of th.e breaker 3, controlAed so as to, cut off the current and.: thus slave the battery voltage. Accordingly, the;: deviation between the battery voltage measured. by he converter 24 and another voltage value (.asymptotic) greater than VI, in memory 23, adjusts the mean,' recharging current;in such a way that the latter vari. es:in the same direction as this deviation, without however exceeding a predetermined m.ximum cutrent for a low battery voltage. 30 Hence., as long as the battery 2 remains discharged, the recharging current holds its maximum value both during the period of duration tc of current-. based control and during the period of duration ta. of. voltage-based control. 35 As a varlant, an extra. generator may be. provided, but noW a voltage generator,. controlled exclusively by the calculating block 22 (the OR gate 26 thus being ornitted) and the battery 2 is recharged froni the current generator 11 controlled by the calculatjng:,block 21, and from the voltage generptor.

During the cycles ta of voltage-based chargillg,.the calculating block 22 here controls the reading of, the memory 23 cyclically so as to compare the batteiry. voltage with the bottom 'threshold voltage VO and with the top threshold valtago VI. Beyond the bottom voltagi' VO (Fig. 4), the generator 1 controlled so as tQ' operate, with the breaker 3, as a voltage generator#..- causes the battery volt'.age to rise again. When the'. latter reaches the top nominal voltage threshold V l.,, here 4.3 V, the calculating block 22 activates a' timeout circuit, not represented, so as to allow the.. voltage to vary beyond the top' threthold V1 for the.,. predetermined duration Ts, here 0,2 seconds, before. allowing it to fall back to the bottom threshold VO, by opening the breaker 3. figure 4 illustrates two suchcycles.

As illustration In Figure. 50. the period represented, of voltage-based recharging, comprises. 4n.. alternation of voltage-based chargings and of stoppages of charging, as is illustrated in. figure. 5B, whi.ch. represents the voltage-b4sed recharging current 1 as a. function of the battery voltage of F.igure SA, AS showti" in this Figure SA, the' time to fall.back to the bottom threshold value VO increases after each cuprent pulse: (of. substantially cons tant duration) so that the mean:current decreases.

When the battery 2 is fully recharged, it$ voltage does not drop back, in the short term, to the.: bottom threshold VO. The subsequent voltage-based.. recharging cycles therefore cor're! pond solely to tht operating steps,, or calcdlation steps, of the circuits.. 22 to 25 always operating according to the envizaged.; sequencing, but having no effect,the breaker. 3' remaining open. Having thus, Initia.1ly, recharged the, battery 2 under a continuous current, possibly a maximumo the current is chopped and hence decreases on,.' average as soon as the top threshold V1 is. reached a - 16.. - f irst time, and the manner of operation becomes eve. r.i more like the purely currexit-ase.d rectiargit..ig manner of operation, explained 6t the start. Any risk of th' thermal destruction of the battery 2 fit therefotd avoided.

The flowchart of Figure 6 Illustratis the' S t 0 P,!9: of the process.

At a step, 61, the sequencer circult 18 determines whether the current Instant t be.longs' tt a.

period ta. If not (period 'to). the output of. t hecalculating block 21 is enabled and that of. the calculating block. 22 is disabled, at a step 62f.. gite 26. The details of the current-based charging arO rot recalled here. Step 62 is looped back to step 61 'whos.e.

Yes output branch 1s followed by a step 63,'.the j.nvpits,e, of step 62, in 'which it is the, output of t.hb calculating block 22 which is enabled. and the output..of, the calculating block 21 Is disabled.

At a next step 64, the breaker 3 is,.closed tor' voltagebased recharging then, in a step P5, the;s-et' 22-25 determines whether the battery voltage V reaches.

1 the top threshold. value V1. lt not, we 'loop badk:ti::.

step 61 and thus go back periodically to step 6. If. the answer is yed, at this:step 65, the 0. 2 'a (T!s) timeout circuit is activated. at. a step P6 and 'this:.':.,circuit then compares,: at a atep 57, the va.1 u e o-.f the: time elapsed with the value Ta. I.f the value TS 14 no t. reached, we loop back here to step 61 (or to a lot.ail, equivalent step) to check that. we are still in t h 0 period ta of volt4ge-based. char-gng and, likewise, Me' go back to step 67. The No brnch of step 6.7 could,;as' an option, be looped back to tlni; .step.67 since hete.Ts' Is much less than ta and than tc: 'ta could overshoot onto to. The Yes output branch of step 67 is followed by a step 68 for resetting the tizn,eout circuit to zero and for opening the breaker.3. At a next step 9 ye determine whether. the battery voltage V reaches 'ho bottom threshold Voltage VO. If not, we 1Qop back to,.. step 61 for a new elementary. volta:ge-based. recha.rgring.;.

cycle, similar to one of the three cycles of Figure 5A.... If the answer is.'yest in step 69, we test locally, in d' step 70, as to whether the current instant still.--belongs to the period ta so as, if it does, to loop:' back to step 69... Hende, there is no. reclocure of the... breake. r 3 while the battery voltage V remains greater... than the bpttom threshold VO. The negative branch of:step 70 is looped' back to the negative bran.ch of th.e. counterpart step 61, here via step Cl..

If, In step 69o the battery voltaggR V 1.9 1ess than the bottom threshold VO, we loop back to step '61 so as subsequentl ' to close the breaker 3 in step'.64, y thereby recommencing, the voltagi- ibased rechargin4,.,' procedure.

: '.... ',. 1 i 1..

- is - CLADW 1 Process tor controning the recharging of a battery from a generator., in which proces.s n - the battery' is charged alternately aid cyclically based on current and on v91tage, - during the v,oltage-ba'sed charging cycles, the charging voltage is Allowed to 'Vary and., beyond. a bottom threshold, it Is allowed to'vary)peyond a top threshold for a predetermited duration before allowing it to fall back to thd..bottom thresholl - during the current-baged charging 'cycles, the. value of the charging current j,s varied cyclically from,,. an initial value,, - the temperature of the battery monitored so as to search for and measure therein a.

corresponding variation, 6f the temperature,' and, - the value of the current Is redticed if the temperature variat.lon.' ciCeeds a target threshcfld

Claims (1)

1. 2. Process a ccording to. Claim 1, in which value of the temperature

   varia.ti.bn Is slaved to the threshold value, by adj.usting the current n' accordance with the deviation, between. the 'sa.id temperature values.

   3. Process according to one of Claims 1 and 2, in which the value. of the temperature variation' is determined 1by comparison between a beating slope and a cooling slope.

   4, Process according to one of Claims 1 to 3, in which the battery is r6charged from acurrent.

   generator and from a voltacle generator'.

   5. Process according to one of Claims.1 to 3, n which the battery is rethaxged from a cuz;:eiit generator and ú rom a voltaqe-based slaving by rteans of the current generator.

   6. Device for controlling. recharging of a battery configured so as to be supplied by a generator comprising 1 i:: '..

   - means of variation recharging current, - sequencer means f or varying th, for - cyclIC4il.l,, controlling the means of variation., - means for providing a chargin' voltage., means for measuring the devia'tioP'.

   between the charging voltage:of the battery an.

   bottom (V0) and top (V1) thresholds of charging, voltage, - means the battery., of measuring.the te:mperature. of means of providing. a target. threshold value for temperature modulation of thie; battery and - means of calculation.

   linked at ihput to the t.h:eshbld-providing meanw and- to, the temperature-measuring means. so as to deterinine therefrom a. temperature variAtion value.,-.

   and to control means of adjusting th e', current in accordance with the deviation between th temperature variation and the threshold value, and.

   thereby, under the action of the means for measuring".

   the temperature deviation, to control the meahs of providing tht chargin.voltage.

   7. Device according: to..Claim 6, current generator and a voltage. generat'or.

   cc. mprising a Device according: to Claim. 6,: comprising current generator and a voltage-based slaying by means.' 30 of the current generator..

   9.. Process for controlling the recharging of a battery substantially as herein described with 'reference to the accompanying drawings.

   10. Device for controlling the recharging of a battery substantially as herein described with reference to the accompanying drawings,