Samlexpower BBM-1225 - Operation and Protections; Operation; Protecting the Battery Against Deep Discharge; Overload and Short Circuit Protection

8 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 9
SECTION 5 | Operation and Protections
5.1 OPERATION
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CAUTION!
 Pleaseensurethattheratedoutputcurrentofthe12VDCor24VDCpower
supplyisonlyupto25A.
AsalreadystatedatinSection3.1,thisunitisapassivedeviceandfunctionsonlyasan
interfacebetweentheexternalpowersupply,thebatteryandtheDCload.
SwitchONtheexternalpowersupplytopowerontheloadandalsotostartcharging
thebattery.IfthepowersupplyfailsorisswitchedOFF,theloadwillbeimmediatelyfed
bythebattery.Whentheloadissuppliedbythebattery,thebatterywillstartdraining
anditsvoltagewillcontinuetodrop.Duringthistime,thevoltageattheLoadTerminals
(4&3,Fig2.2)willbeupto0.5VlowerthanthevoltageattheBatteryTerminals(5&3,
Fig2.2)duetotheForwardVoltageDropacrosstheinternalSchottkyDiodeD2.
5.2 PROTECTING THE BATTERY AGAINST DEEP DISCHARGE
Forlongerlife,LeadAcidBatteriesshouldnotbeallowedtodischargemorethan
80%.Forexample,a12V/24VloadedbatteryatloadcurrentofC/10Amps(CistheAh
capacity)willbe100%dischargedataround11V/22Vand80%dischargedat11.5V/23V.
Itisrecommendedthatasuitable“LowVoltageDisconnectDevice”,alsocalled“Battery
Guard”,maybeusedinserieswithPositivelineoftheloadforprotectionagainstdeep
dischargeofthebattery.Battery Guard, Model No. BG-40, made by Samlex America, Inc.
may be considered.
5.3 OVERLOAD AND SHORT CIRCUIT PROTECTION
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INFO
 Explanationgivenbelowisbasedonuseofexternalpowersupplywith
“ConstantCurrentLimit”valueof25A.InaConstantCurrentLimitedPower
Supply,whentheCurrentLimitvalueisreached,theoutputvoltagewillnotbe
regulatedandwilldrop.
Iftheloadtriestodrawcurrenthigherthanthecurrentlimitvalueoftheexternal
powersupply(25A),theoutputvoltageoftheexternalpowersupplywillnotbe
regulatedandthevoltageattheLoadTerminals(4&3,Fig2.2)willdrop.Portionof
overloadcurrentbeyondthecurrentlimitvalueoftheexternalpowersupply(25A)
willnowbefedfromthebatteryandthebatterywillstartdrainingatthisdifferential
current.ThevoltageattheBatteryTerminals(5&3,Fig2.2)willstartdroppingandwill
beequaltothevoltagecorrespondingtostateofdischargeofthebattery.Thevoltage
attheLoadTerminals(4&3,Fig2.2)willbeupto0.5VbelowthevoltageattheBattery
Terminals(5&3,Fig2.2).External25AFuse(F2)ontheloadsidewillblow.