A. DCGeneration(continued)
19. ChargingBattery
A battery'scapacityis measured in amperehours(AH),whichisthe productof the numberof ampsflowingandthe hoursthis currentflows. Thechargerequiredis also measuredin ampere hoursand isalwayssomewhatlargerthanthe dischargeobtainable.Theamountof recharge
requiredat normalratesand temperatures is 140% of the dischargeobtainable.
Voltagesvalues,currents,etc,referto Chart 4. Chargingis mostefficientwhenperformedat batterytemperaturesbetween+40°Fand+80°F. Donot startcharging,exceptwhen necessary,if the batterytemperatureis above 100°F.
Donotchargea nickelcadmiumbatteryin the proximityof leadacid batteries. Fumesor acid spillagecan exist to contaminatethe nickelcadmiumbattery. If the sameequipmentis usedto
chargebothtypesof batteries.cleanthoroughlywith a sodiumbicarbonatesolutionbeforeusing it on nickel cadmiumbatteries. Thereareseveralmethodsusedto chargethis typeof battery. The preferredmethodand an alternatemethodarepresentedin Figure301.
20. ConstantCurrentCharging
If batterycharge isunknown,completelydischargethe batterybeforecharging.
(a)
Chargebatteryat 13.3 ampsuntilbatteryvoltagereachescontrolpoint(30.5volts).
(b)
Thefinishingchargeratewill be 4 amps. Todeterminetimeto fully chargebatteryat finishing rate,usethe followingformula:
Tf -Time,in hoursrequiredforfinishingcharge.
Tf = Is x Ts 3 x If Is -Startingchargerate,in amps. Ts -Time, in hours,of charge atthe startinguntil "ControlPoint"voltageis
reached.
If -Rate, in amps, of finishingcharge.
NOTE: For furtherinformationon batteryreferto SAFToperatingand maintenancemanual, P/N DC 3-01-78-3176-5 A.
21. ConstantPotentialCharging
(a)
Chargethe batteryfor 4 hoursat propervoltage(referto Chart 4). Thechargershouldbe able to deliver a minimumof 43amps.
(b)
A nearlyfull chargemaybe restoredin one hourif the chargeris capable of delivering86 amps.
(c)
A batteryin a dischargedstatewill accept veryhighcurrents,for a few minutes,atthe beginningof the charge (350ampsmaximumin rushcurrent). Thiscurrentdoesnotdamage
the battery,butthe chargershouldhaveinherentcurrentlimitingorbe otherwiseprotected againstoverload.
EFFECTIVITY:
24-30-00PAGE
Jan10/90
PIPER AIRCRAFT
PA-42-720(Advanced Trainer)
MAINTENANCEMANUAL
A. DC Generation (continued)
22. BatteryCellReplacement
WARNING: TO AVOIDPERSONALINJURYOR BATTERYDAMAGE,DO NOTREMOVEA CELLOR TERMINALLUGSFROMA CHARGED BATTERY.WEARSAFETY GOGGLESAND PROTECTIVECLOTHINGTO PROTECT EYESANDBODY FROMANY ELECTROLYTESPRAYSQUEEZEDFROMREPLACEMENTCELL WHENITIS PUSHED INTOPLACE.
CAUTION: DO NOT REMOVEDEFECTIVECELL FROMBATTERYUNTILA PROPER REPLACEMENTCELLIS AVAILABLE (REFERTO PARTS CATALOGFOR CORRECTPARTNUMBER).
(a)
Dischargebatteryat 20 amps for 2 hours.
(b)
With clip leads,short acrosseachcell as voltage goesbelow1/2 volt.
(c)
After allcells are shorted, removeconnectingstrapsfromdefectivecell.
(d)
Liftdefectivecell frombatteryby liftingat terminalsusinga speciallyfabricatedtool (referto Figure 302).
(e)
Installnewcell ensuringit is discharged and polaritysymbolsareproperlypositioned.
NOTE: Toaid insertion, be sure vents on all cellsin the same row, includingreplacementcell, are loosened.
(f)
If cell is difficultto install, applyvaselineor Shell Dorina2 on sides of replacementcell.
(g)
Reassembleattachinghardware.
NOTE: Theseparts arespecificallydesignedto providean adequate electricalconnection. Neverusehomemadehardware.
Socket screw terminals
(2 required)
Appropriate thread(5/16)
FabricatedCell PullerTool
Figure 302
EFFECTIVITY:
Jan 10/90 24-30 00
Jan 10/90
PIPER AIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCE MANUAL
A. DC Generation (continued)
THERMOSTAT
FUSEHOLDER
I
Cell Layout -Nickel Cadmium Battery
Figure 303
23. Removal of Battery
The battery is located behind the nose cone.
(a)
Openforwardbaggagecompartmentdoor.
(b)
Releasenosecone latch located immediatelyto the left, inside the baggage compartmentdoor.
(c)
Swingopen nose cone, cut safety wire on large Elconelectrical connector and unplug connector.
(d)
Locatesinglewire (in line connector)to battery temperatureprobe and disconnect the wire ends.
(e)
Turncamlocksloose at bottomfrontof battery and remove battery supportangle.
(f)
Slidebatteryforwardon tracks andwithdrawfromnose section. Be careful,batteryweightis considerable.
24. Installationof Battery
(a)
Placebatteryon mounting bracket and reconnectvent lines previouslyremoved.
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