Ni-Cd Ba lie des U George Wilson NICKEL-CADMIUM Ni-Cd cells/batteries developed space program come sizes shapes have uses development has extensive has resulted cells/batteries have long life under difficult environmental conditions temperature shock vibration etc timing fortunate hobby As more-sophisticated radio control equipment introduced economical reliable power source ready Ni-Cd wet cells covered article good batteries starter motor glow plug igniters Light-duty Ni-Cds like used RC transmitters airborne radio systems have extensive recharge capabilitiesespecially transmitters approach 1000 recharges sometimes claimed Ni-Cd literature have retired transmitter batteries still worked well after seven seasons Airborne batteries less likely provide long life primarily because subjected mechanical shock vibration Todays dry Ni-Cd cells manufactured three different ways 1 traditional slowcharge overnight 14-16 hours type 2 fast-charge type 3 high-capacity type slow-charge type have enough internal resistance cause undesirable amount heating during fast charge discharge well role RC system batteries Fast-charge types have relatively low internal resistance better able withstand fast charging/discharging recommended powering Electric flight motors high-capacity types useful applications require long discharge times little no increase size typically RC Soaring models Ni-Cds used Electric models less likely provide long life addition shock vibration subject heat during discharge during overcharge Ni-Cds designed service seem operate little short-term capacity degradation Well managed batteries service last years used occasional basis includes avoidance overcharging charging batteries hot Memory long after Ni-Cd batteries introduced use RC modeling myth tho o,thnr rnnhin floninn hulill Ann ted about having memory problem myth states regularly draw small amount capacity before recharging will become incapable deep dischargesunable supply full capacity Most Ni-Cd experts agree memory does exist except certain high-tech applications see sidebar Ni-Cd cells have three failure modes Remember battery consists two cells connected series First fail opentheir voltage goes zero close it becomes impossible recharge Charging current will pass through open cell exists battery battery voltage will zero close single cell will impossible recharge battery type failure occurs because overcharging total wearout cause failure mechanical open circuit loss electrolyte small amount liquid chemical allows current flow through cell has vented out cell frequently evidenced white powder accumulates around positive tenninal obvious open-type failure broken wire between cells open circuit inside cell type failure frequently occurs airborne packs vibration present writer has pointed out spot-welded strip-type interconnection between cells particularly prone vibration failure recommends soldered connections used Use bit paste-type flux eg NoKrode little heat possible clean off residual flux second failure mode shorted frequent failure mode results crystals aka dendrites forming electrolyte passing through separator between cells positive negative electrodes crystals cause short circuit between electrodes voltage across cell goes zero close charging normal charging rate say /io rated current will cause cell recharge type failure occurs often during storage during periods tricklecharging Typically 48- 96-volt batteries will supply 36 84 volts May 1998 43 12-volt Ni-Cd battery electric motors shown 48-volt 100 mAh airborne battery gliders D cell Typical 96-volt Ni-Cd transmitter battery almost ideal environmentlittle shock vibration Battery cases held transmitter back Velcrot0 discharging shorted cell will produce no voltage will allow current flow through Note charged battery eight fewer cells shorted cell produces less voltage allowable minimum 11 volts per cell have methods used fix shorted Ni-Cd cells Most experts agree cell has shorted internally has fixed cell should used critical applications Use flashlight never alrborne RC system Shorted cells have traditionally fixed charging large capacitor several thousand microfarads 10 12 volts discharging plus-to-plus across shorted cell usually clears short cell will act normally thereafter favorite method use currentcontrolled bench power supply has voltmeter ammeter current llmiting cell placed across supply plus-to plus current through increased until voltage across jumps up 12 volts voltage increased watching current After reaching 5 10 amperes CONSTANT-CURRENT DISCHARGE CIRCUIT 24ohm 100 1v ohm ww set 20 ohm Wv fine set circuit useful determine battery cells capacity After fully charging battery cell set discharge current batterys nominal discharge value time long takes battery cell discharge 11 volts per cell discharge time hours times discharge current milliamperes mA will batterys capacity milliampere-hours discharge current measured using milliammeter multimeter set appropriate scale set using variable resistor shown circuit 24 ohm resistor sets maximum current about 300 mA minimum current will less 10 mA variable resistor should rated watt preferably will wire-wound type cannot find resistor values Radio Shack RS can supply substitutes LM 317 IC number 276-1778 24 ohm resistor can made five 10 ohm resistors RS 271-1301 parallel variable resistor can made using four 22 ohm resistors RS 271-1103 wired series switched multiposition switch RS 275-1386 20 ohm variable resistor RS 271-265A fine adjustment See circuit diagram Some transmitters use diode series charging circuits prevent reverse polarity connection charger cases discharger circuit must connected before diode will necessary open transmitter case get proper connection point Use care light cost automatic discharge/charge devices home-brew discharger may well worth effort 44 Model Aviation AA cells constitute 48-volt airborne Ni-Cd battery Five cells would increase servo powerand battery drain CONSTANT CURRENT LOAD 0 VOM LM 317 coarse set 4-10 ohm 4-22 ohm L1ZA1 Substitute Parts See text voltage control dropped way voltmeter will show 12 volts short has cleared couple trips high current may good insurance method can used sizes Ni-Cd cells great rejuvenating cells hand tools flashlights using overvoltage/overcurrent method fix shorted cell cell should show no perceptible heating maximum life NiCd batteries/cells should charged manner causes heat above about 1000 Fahrenheit Above level electrolyte cell may vented through cells seal Fast-charging beyond full charge consequent heating will shorten batterys life Luckily Ni-Cds cool during charge below full charge heat above full charge during discharge Modem fast-charge Ni-Cds designed handle moderate overcharging overcharging extent heating occurs should still avoided third failure mode wear out mode cell becomes leaky discharges itself rapidly becomes partially shorted appearance grayish powder around positive terminal indicator condition Time retire cell/battery cell new and/or good condition will hold its charge extended period typically week two old and/or wellused cell may lose its charge day mechanism appears barrier between electrodes becomes partially conductive Cells condition appear accept full charge checked constant current load voltmeter timed determine long takes discharge 11 volts per cell will have less rated capacity good cell will have its rated capacity sometimes cell will produce 80 percent its rated capacity time get new cell battery cells same age Remember cells bearing same label same lot created equal Variations order 10% up down have observed new cells lucky enough own battery management system Ace R/C Digipace FMD Einstein similar device determination battery capacity easy make devices expensive may want build constantdischarge circuit like the sidebar lacks automatic features will job Cycling Cycling deep discharging 11 volts per cell will frequently improve batterys capacity essential cells/batterys well-being like technique used remove shorts partial shorts appear get burned off care feeding power packs some users advise running motor end flight until loses speed Others think unnecessary am Electric flier wont take sides youre through day power batteries should charged C/l0 rate going fly again charging C/3 usual cells have carefully matched capacity inevitable Cycling/Memory Red Scholefield Among users batteries both industrial consumer sectors idea memory phenomenon nickelcadmium batteries has widely misused misunderstood term memory has become buzzword used describe raft application problems often being confused simple voltage depression suspect memory myth will continue survive grow benefit gadget gizmo manufacturers claiming recondition Ni-Cd packs RC systems suggests some breakthrough will eliminate battery problems forever Frequently articles appear hobby publications addressing selection care maintenance critical part RC system products being introduced enhance performance Ni-Cd cells Sophisticated charging schemes conditioning devices performance analyzers pulse reflex charge burp dememorize initialize stimulate receiver transmitter packs achieve ultimate reliability no effort part modeler Sony guyslife doesnt work way unfortunately neither batteries Cycling often given way get rid memory cleans out anxiety closet thing cycling does reduce voltage depression came agglomeration crystal structure active material lattice long-term overcharge shallow discharges will low man totem pole use high-tech charging equipment poorer cell will fully charged others peak out indicated temperature rise end charge voltage peak cycle continued flight will shorter previous deviation cell capacity serious flight times will degrade rapidly possible damage ailing cell good practice equalize cells after days use charging C/10 least overnight cycle pack deep discharge 11 volts per cell recharge pack C/b So people insist memory really exists explanation probably first third failure mode cell falls rapidly because lealry battery voltage drops about 12 volts puffing below 11 volt per cell minimum allowable voltage level point bad cell being charged backwards battery drained further will make worse Recharging battery full output voltage will restore battery briefly will discharge again very rapidly hence apparent memory phenomenon cell voltages measured individually after rapid discharge occurrences will easy locate errant cell cell maybe individually defective battery has well used old time replace battery other cells probably close failure Some Helpful Facts Current drains nominal approximate Transmitter100-150 mA Receiver5-30 mA Servos5-20 mA idle Note 1 up 1000 mA restricted Recharging efficiency 40-60% energy required recharge used Charge rates C capacity Ah mAh Trickle continuous C/50 Slow ovemight 14-16 hoursNote 2C/l0 Quick 3-6 hoursNote 3 C/3 C/6 Fast 1 hour 6 minutesNotes 3 4 CtoCX1O Storage Store cool place less 700 F High temperatures promote self-discharge Occasional cycling during storage helps Minimum safe voltage measured under load directly after use Four-cell receiver battery 46 volts Eight-cell transmitter battery 92 volts Normal no-load voltage per cell after charging 135 volts Nominal discharge voltage per cell 12 volts Minimum discharge voltage per cell Note 5 11 volts Notes I Coreless special designs may much double drain 2 Several days rate causes little no damage 3 Overcharging rate damaging 4 Must stopped immediately full charge heating damage will occur 5 Careful discharge zero volts permissible cell discharged separately Thanks counselors Hans Sagamuehl Red Scholefield Neil Whitman help advice during preparation article ge Wilson 82 Frazier Way Marstons Mills MA 02648 geowilson @juno corn May 1998 45
Edition: Model Aviation - 1998/05
Page Numbers: 43, 44, 45
Edition: Model Aviation - 1998/05
Page Numbers: 43, 44, 45
Ni-Cd Ba lie des U George Wilson NICKEL-CADMIUM Ni-Cd cells/batteries developed space program come sizes shapes have uses development has extensive has resulted cells/batteries have long life under difficult environmental conditions temperature shock vibration etc timing fortunate hobby As more-sophisticated radio control equipment introduced economical reliable power source ready Ni-Cd wet cells covered article good batteries starter motor glow plug igniters Light-duty Ni-Cds like used RC transmitters airborne radio systems have extensive recharge capabilitiesespecially transmitters approach 1000 recharges sometimes claimed Ni-Cd literature have retired transmitter batteries still worked well after seven seasons Airborne batteries less likely provide long life primarily because subjected mechanical shock vibration Todays dry Ni-Cd cells manufactured three different ways 1 traditional slowcharge overnight 14-16 hours type 2 fast-charge type 3 high-capacity type slow-charge type have enough internal resistance cause undesirable amount heating during fast charge discharge well role RC system batteries Fast-charge types have relatively low internal resistance better able withstand fast charging/discharging recommended powering Electric flight motors high-capacity types useful applications require long discharge times little no increase size typically RC Soaring models Ni-Cds used Electric models less likely provide long life addition shock vibration subject heat during discharge during overcharge Ni-Cds designed service seem operate little short-term capacity degradation Well managed batteries service last years used occasional basis includes avoidance overcharging charging batteries hot Memory long after Ni-Cd batteries introduced use RC modeling myth tho o,thnr rnnhin floninn hulill Ann ted about having memory problem myth states regularly draw small amount capacity before recharging will become incapable deep dischargesunable supply full capacity Most Ni-Cd experts agree memory does exist except certain high-tech applications see sidebar Ni-Cd cells have three failure modes Remember battery consists two cells connected series First fail opentheir voltage goes zero close it becomes impossible recharge Charging current will pass through open cell exists battery battery voltage will zero close single cell will impossible recharge battery type failure occurs because overcharging total wearout cause failure mechanical open circuit loss electrolyte small amount liquid chemical allows current flow through cell has vented out cell frequently evidenced white powder accumulates around positive tenninal obvious open-type failure broken wire between cells open circuit inside cell type failure frequently occurs airborne packs vibration present writer has pointed out spot-welded strip-type interconnection between cells particularly prone vibration failure recommends soldered connections used Use bit paste-type flux eg NoKrode little heat possible clean off residual flux second failure mode shorted frequent failure mode results crystals aka dendrites forming electrolyte passing through separator between cells positive negative electrodes crystals cause short circuit between electrodes voltage across cell goes zero close charging normal charging rate say /io rated current will cause cell recharge type failure occurs often during storage during periods tricklecharging Typically 48- 96-volt batteries will supply 36 84 volts May 1998 43 12-volt Ni-Cd battery electric motors shown 48-volt 100 mAh airborne battery gliders D cell Typical 96-volt Ni-Cd transmitter battery almost ideal environmentlittle shock vibration Battery cases held transmitter back Velcrot0 discharging shorted cell will produce no voltage will allow current flow through Note charged battery eight fewer cells shorted cell produces less voltage allowable minimum 11 volts per cell have methods used fix shorted Ni-Cd cells Most experts agree cell has shorted internally has fixed cell should used critical applications Use flashlight never alrborne RC system Shorted cells have traditionally fixed charging large capacitor several thousand microfarads 10 12 volts discharging plus-to-plus across shorted cell usually clears short cell will act normally thereafter favorite method use currentcontrolled bench power supply has voltmeter ammeter current llmiting cell placed across supply plus-to plus current through increased until voltage across jumps up 12 volts voltage increased watching current After reaching 5 10 amperes CONSTANT-CURRENT DISCHARGE CIRCUIT 24ohm 100 1v ohm ww set 20 ohm Wv fine set circuit useful determine battery cells capacity After fully charging battery cell set discharge current batterys nominal discharge value time long takes battery cell discharge 11 volts per cell discharge time hours times discharge current milliamperes mA will batterys capacity milliampere-hours discharge current measured using milliammeter multimeter set appropriate scale set using variable resistor shown circuit 24 ohm resistor sets maximum current about 300 mA minimum current will less 10 mA variable resistor should rated watt preferably will wire-wound type cannot find resistor values Radio Shack RS can supply substitutes LM 317 IC number 276-1778 24 ohm resistor can made five 10 ohm resistors RS 271-1301 parallel variable resistor can made using four 22 ohm resistors RS 271-1103 wired series switched multiposition switch RS 275-1386 20 ohm variable resistor RS 271-265A fine adjustment See circuit diagram Some transmitters use diode series charging circuits prevent reverse polarity connection charger cases discharger circuit must connected before diode will necessary open transmitter case get proper connection point Use care light cost automatic discharge/charge devices home-brew discharger may well worth effort 44 Model Aviation AA cells constitute 48-volt airborne Ni-Cd battery Five cells would increase servo powerand battery drain CONSTANT CURRENT LOAD 0 VOM LM 317 coarse set 4-10 ohm 4-22 ohm L1ZA1 Substitute Parts See text voltage control dropped way voltmeter will show 12 volts short has cleared couple trips high current may good insurance method can used sizes Ni-Cd cells great rejuvenating cells hand tools flashlights using overvoltage/overcurrent method fix shorted cell cell should show no perceptible heating maximum life NiCd batteries/cells should charged manner causes heat above about 1000 Fahrenheit Above level electrolyte cell may vented through cells seal Fast-charging beyond full charge consequent heating will shorten batterys life Luckily Ni-Cds cool during charge below full charge heat above full charge during discharge Modem fast-charge Ni-Cds designed handle moderate overcharging overcharging extent heating occurs should still avoided third failure mode wear out mode cell becomes leaky discharges itself rapidly becomes partially shorted appearance grayish powder around positive terminal indicator condition Time retire cell/battery cell new and/or good condition will hold its charge extended period typically week two old and/or wellused cell may lose its charge day mechanism appears barrier between electrodes becomes partially conductive Cells condition appear accept full charge checked constant current load voltmeter timed determine long takes discharge 11 volts per cell will have less rated capacity good cell will have its rated capacity sometimes cell will produce 80 percent its rated capacity time get new cell battery cells same age Remember cells bearing same label same lot created equal Variations order 10% up down have observed new cells lucky enough own battery management system Ace R/C Digipace FMD Einstein similar device determination battery capacity easy make devices expensive may want build constantdischarge circuit like the sidebar lacks automatic features will job Cycling Cycling deep discharging 11 volts per cell will frequently improve batterys capacity essential cells/batterys well-being like technique used remove shorts partial shorts appear get burned off care feeding power packs some users advise running motor end flight until loses speed Others think unnecessary am Electric flier wont take sides youre through day power batteries should charged C/l0 rate going fly again charging C/3 usual cells have carefully matched capacity inevitable Cycling/Memory Red Scholefield Among users batteries both industrial consumer sectors idea memory phenomenon nickelcadmium batteries has widely misused misunderstood term memory has become buzzword used describe raft application problems often being confused simple voltage depression suspect memory myth will continue survive grow benefit gadget gizmo manufacturers claiming recondition Ni-Cd packs RC systems suggests some breakthrough will eliminate battery problems forever Frequently articles appear hobby publications addressing selection care maintenance critical part RC system products being introduced enhance performance Ni-Cd cells Sophisticated charging schemes conditioning devices performance analyzers pulse reflex charge burp dememorize initialize stimulate receiver transmitter packs achieve ultimate reliability no effort part modeler Sony guyslife doesnt work way unfortunately neither batteries Cycling often given way get rid memory cleans out anxiety closet thing cycling does reduce voltage depression came agglomeration crystal structure active material lattice long-term overcharge shallow discharges will low man totem pole use high-tech charging equipment poorer cell will fully charged others peak out indicated temperature rise end charge voltage peak cycle continued flight will shorter previous deviation cell capacity serious flight times will degrade rapidly possible damage ailing cell good practice equalize cells after days use charging C/10 least overnight cycle pack deep discharge 11 volts per cell recharge pack C/b So people insist memory really exists explanation probably first third failure mode cell falls rapidly because lealry battery voltage drops about 12 volts puffing below 11 volt per cell minimum allowable voltage level point bad cell being charged backwards battery drained further will make worse Recharging battery full output voltage will restore battery briefly will discharge again very rapidly hence apparent memory phenomenon cell voltages measured individually after rapid discharge occurrences will easy locate errant cell cell maybe individually defective battery has well used old time replace battery other cells probably close failure Some Helpful Facts Current drains nominal approximate Transmitter100-150 mA Receiver5-30 mA Servos5-20 mA idle Note 1 up 1000 mA restricted Recharging efficiency 40-60% energy required recharge used Charge rates C capacity Ah mAh Trickle continuous C/50 Slow ovemight 14-16 hoursNote 2C/l0 Quick 3-6 hoursNote 3 C/3 C/6 Fast 1 hour 6 minutesNotes 3 4 CtoCX1O Storage Store cool place less 700 F High temperatures promote self-discharge Occasional cycling during storage helps Minimum safe voltage measured under load directly after use Four-cell receiver battery 46 volts Eight-cell transmitter battery 92 volts Normal no-load voltage per cell after charging 135 volts Nominal discharge voltage per cell 12 volts Minimum discharge voltage per cell Note 5 11 volts Notes I Coreless special designs may much double drain 2 Several days rate causes little no damage 3 Overcharging rate damaging 4 Must stopped immediately full charge heating damage will occur 5 Careful discharge zero volts permissible cell discharged separately Thanks counselors Hans Sagamuehl Red Scholefield Neil Whitman help advice during preparation article ge Wilson 82 Frazier Way Marstons Mills MA 02648 geowilson @juno corn May 1998 45
Edition: Model Aviation - 1998/05
Page Numbers: 43, 44, 45
Ni-Cd Ba lie des U George Wilson NICKEL-CADMIUM Ni-Cd cells/batteries developed space program come sizes shapes have uses development has extensive has resulted cells/batteries have long life under difficult environmental conditions temperature shock vibration etc timing fortunate hobby As more-sophisticated radio control equipment introduced economical reliable power source ready Ni-Cd wet cells covered article good batteries starter motor glow plug igniters Light-duty Ni-Cds like used RC transmitters airborne radio systems have extensive recharge capabilitiesespecially transmitters approach 1000 recharges sometimes claimed Ni-Cd literature have retired transmitter batteries still worked well after seven seasons Airborne batteries less likely provide long life primarily because subjected mechanical shock vibration Todays dry Ni-Cd cells manufactured three different ways 1 traditional slowcharge overnight 14-16 hours type 2 fast-charge type 3 high-capacity type slow-charge type have enough internal resistance cause undesirable amount heating during fast charge discharge well role RC system batteries Fast-charge types have relatively low internal resistance better able withstand fast charging/discharging recommended powering Electric flight motors high-capacity types useful applications require long discharge times little no increase size typically RC Soaring models Ni-Cds used Electric models less likely provide long life addition shock vibration subject heat during discharge during overcharge Ni-Cds designed service seem operate little short-term capacity degradation Well managed batteries service last years used occasional basis includes avoidance overcharging charging batteries hot Memory long after Ni-Cd batteries introduced use RC modeling myth tho o,thnr rnnhin floninn hulill Ann ted about having memory problem myth states regularly draw small amount capacity before recharging will become incapable deep dischargesunable supply full capacity Most Ni-Cd experts agree memory does exist except certain high-tech applications see sidebar Ni-Cd cells have three failure modes Remember battery consists two cells connected series First fail opentheir voltage goes zero close it becomes impossible recharge Charging current will pass through open cell exists battery battery voltage will zero close single cell will impossible recharge battery type failure occurs because overcharging total wearout cause failure mechanical open circuit loss electrolyte small amount liquid chemical allows current flow through cell has vented out cell frequently evidenced white powder accumulates around positive tenninal obvious open-type failure broken wire between cells open circuit inside cell type failure frequently occurs airborne packs vibration present writer has pointed out spot-welded strip-type interconnection between cells particularly prone vibration failure recommends soldered connections used Use bit paste-type flux eg NoKrode little heat possible clean off residual flux second failure mode shorted frequent failure mode results crystals aka dendrites forming electrolyte passing through separator between cells positive negative electrodes crystals cause short circuit between electrodes voltage across cell goes zero close charging normal charging rate say /io rated current will cause cell recharge type failure occurs often during storage during periods tricklecharging Typically 48- 96-volt batteries will supply 36 84 volts May 1998 43 12-volt Ni-Cd battery electric motors shown 48-volt 100 mAh airborne battery gliders D cell Typical 96-volt Ni-Cd transmitter battery almost ideal environmentlittle shock vibration Battery cases held transmitter back Velcrot0 discharging shorted cell will produce no voltage will allow current flow through Note charged battery eight fewer cells shorted cell produces less voltage allowable minimum 11 volts per cell have methods used fix shorted Ni-Cd cells Most experts agree cell has shorted internally has fixed cell should used critical applications Use flashlight never alrborne RC system Shorted cells have traditionally fixed charging large capacitor several thousand microfarads 10 12 volts discharging plus-to-plus across shorted cell usually clears short cell will act normally thereafter favorite method use currentcontrolled bench power supply has voltmeter ammeter current llmiting cell placed across supply plus-to plus current through increased until voltage across jumps up 12 volts voltage increased watching current After reaching 5 10 amperes CONSTANT-CURRENT DISCHARGE CIRCUIT 24ohm 100 1v ohm ww set 20 ohm Wv fine set circuit useful determine battery cells capacity After fully charging battery cell set discharge current batterys nominal discharge value time long takes battery cell discharge 11 volts per cell discharge time hours times discharge current milliamperes mA will batterys capacity milliampere-hours discharge current measured using milliammeter multimeter set appropriate scale set using variable resistor shown circuit 24 ohm resistor sets maximum current about 300 mA minimum current will less 10 mA variable resistor should rated watt preferably will wire-wound type cannot find resistor values Radio Shack RS can supply substitutes LM 317 IC number 276-1778 24 ohm resistor can made five 10 ohm resistors RS 271-1301 parallel variable resistor can made using four 22 ohm resistors RS 271-1103 wired series switched multiposition switch RS 275-1386 20 ohm variable resistor RS 271-265A fine adjustment See circuit diagram Some transmitters use diode series charging circuits prevent reverse polarity connection charger cases discharger circuit must connected before diode will necessary open transmitter case get proper connection point Use care light cost automatic discharge/charge devices home-brew discharger may well worth effort 44 Model Aviation AA cells constitute 48-volt airborne Ni-Cd battery Five cells would increase servo powerand battery drain CONSTANT CURRENT LOAD 0 VOM LM 317 coarse set 4-10 ohm 4-22 ohm L1ZA1 Substitute Parts See text voltage control dropped way voltmeter will show 12 volts short has cleared couple trips high current may good insurance method can used sizes Ni-Cd cells great rejuvenating cells hand tools flashlights using overvoltage/overcurrent method fix shorted cell cell should show no perceptible heating maximum life NiCd batteries/cells should charged manner causes heat above about 1000 Fahrenheit Above level electrolyte cell may vented through cells seal Fast-charging beyond full charge consequent heating will shorten batterys life Luckily Ni-Cds cool during charge below full charge heat above full charge during discharge Modem fast-charge Ni-Cds designed handle moderate overcharging overcharging extent heating occurs should still avoided third failure mode wear out mode cell becomes leaky discharges itself rapidly becomes partially shorted appearance grayish powder around positive terminal indicator condition Time retire cell/battery cell new and/or good condition will hold its charge extended period typically week two old and/or wellused cell may lose its charge day mechanism appears barrier between electrodes becomes partially conductive Cells condition appear accept full charge checked constant current load voltmeter timed determine long takes discharge 11 volts per cell will have less rated capacity good cell will have its rated capacity sometimes cell will produce 80 percent its rated capacity time get new cell battery cells same age Remember cells bearing same label same lot created equal Variations order 10% up down have observed new cells lucky enough own battery management system Ace R/C Digipace FMD Einstein similar device determination battery capacity easy make devices expensive may want build constantdischarge circuit like the sidebar lacks automatic features will job Cycling Cycling deep discharging 11 volts per cell will frequently improve batterys capacity essential cells/batterys well-being like technique used remove shorts partial shorts appear get burned off care feeding power packs some users advise running motor end flight until loses speed Others think unnecessary am Electric flier wont take sides youre through day power batteries should charged C/l0 rate going fly again charging C/3 usual cells have carefully matched capacity inevitable Cycling/Memory Red Scholefield Among users batteries both industrial consumer sectors idea memory phenomenon nickelcadmium batteries has widely misused misunderstood term memory has become buzzword used describe raft application problems often being confused simple voltage depression suspect memory myth will continue survive grow benefit gadget gizmo manufacturers claiming recondition Ni-Cd packs RC systems suggests some breakthrough will eliminate battery problems forever Frequently articles appear hobby publications addressing selection care maintenance critical part RC system products being introduced enhance performance Ni-Cd cells Sophisticated charging schemes conditioning devices performance analyzers pulse reflex charge burp dememorize initialize stimulate receiver transmitter packs achieve ultimate reliability no effort part modeler Sony guyslife doesnt work way unfortunately neither batteries Cycling often given way get rid memory cleans out anxiety closet thing cycling does reduce voltage depression came agglomeration crystal structure active material lattice long-term overcharge shallow discharges will low man totem pole use high-tech charging equipment poorer cell will fully charged others peak out indicated temperature rise end charge voltage peak cycle continued flight will shorter previous deviation cell capacity serious flight times will degrade rapidly possible damage ailing cell good practice equalize cells after days use charging C/10 least overnight cycle pack deep discharge 11 volts per cell recharge pack C/b So people insist memory really exists explanation probably first third failure mode cell falls rapidly because lealry battery voltage drops about 12 volts puffing below 11 volt per cell minimum allowable voltage level point bad cell being charged backwards battery drained further will make worse Recharging battery full output voltage will restore battery briefly will discharge again very rapidly hence apparent memory phenomenon cell voltages measured individually after rapid discharge occurrences will easy locate errant cell cell maybe individually defective battery has well used old time replace battery other cells probably close failure Some Helpful Facts Current drains nominal approximate Transmitter100-150 mA Receiver5-30 mA Servos5-20 mA idle Note 1 up 1000 mA restricted Recharging efficiency 40-60% energy required recharge used Charge rates C capacity Ah mAh Trickle continuous C/50 Slow ovemight 14-16 hoursNote 2C/l0 Quick 3-6 hoursNote 3 C/3 C/6 Fast 1 hour 6 minutesNotes 3 4 CtoCX1O Storage Store cool place less 700 F High temperatures promote self-discharge Occasional cycling during storage helps Minimum safe voltage measured under load directly after use Four-cell receiver battery 46 volts Eight-cell transmitter battery 92 volts Normal no-load voltage per cell after charging 135 volts Nominal discharge voltage per cell 12 volts Minimum discharge voltage per cell Note 5 11 volts Notes I Coreless special designs may much double drain 2 Several days rate causes little no damage 3 Overcharging rate damaging 4 Must stopped immediately full charge heating damage will occur 5 Careful discharge zero volts permissible cell discharged separately Thanks counselors Hans Sagamuehl Red Scholefield Neil Whitman help advice during preparation article ge Wilson 82 Frazier Way Marstons Mills MA 02648 geowilson @juno corn May 1998 45
