10 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 11
Figure 4.4 above shows a series – parallel connection consisting of four 6V, 200 Ah batteries
to form a 12V, 400 Ah battery bank. Two 6V, 200 Ah batteries, Batteries 1 and 2 are con-
nected in series to form a 12V, 200 Ah battery (String 1). Similarly, two 6V, 200 Ah batteries,
Batteries 3 and 4 are connected in series to form a 12V, 200 Ah battery (String 2). These two
12V, 200 Ah Strings 1 and 2 are connected in parallel to form a 12V, 400 Ah bank.
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Caution!
When 2 or more batteries / battery strings are connected in parallel and are then connected
to an Inverter Charger (See Figs. 4.3 and 4.4 given above), attention should be paid to the
manner in which the Inverter Charger is connected to the battery bank. Please ensure that
if the Positive output cable of the Inverter Charger (Cable “A”) is connected to the Positive
batterypostoftherstbattery(Battery1inFig.4.3)ortothePositivebatterypostofthe
rstbatterystring(Battery1ofString1inFig.4.4),thentheNegativeoutputcableofthe
Inverter Charger (Cable “B”) should be connected to the Negative battery post of the last
battery (Battery 4 as in Fig. 4.3) or to the Negative Post of the last battery string (Battery 4 of
Battery String 2 as in Fig. 4.4). This connection ensures the following:
• Theresistancesoftheinterconnectingcableswillbebalanced.
• Alltheindividualbatteries/batterystringswillseethesameseriesresistance.
• Alltheindividualbatterieswillchargeatthesamechargingcurrentandthus,willbe
charged to the same state at the same time.
• Noneofthebatterieswillseeanoverchargecondition.
If the Positive output cable of the Inverter Charger (Cable “A”) is connected to the Positive
batterypostoftherstbattery(Battery1inFig.4.3)ortothePositivebatterypostofthe
rstbatterystring(Battery1ofString1inFig.4.4),andtheNegativeoutputcableofthe
InverterCharger(Cable“B”)isconnectedtotheNegativebatterypostoftherstbattery
(Battery1asinFig.4.3)ortotheNegativePostoftherstbatterystring(Battery1ofBattery
String 1 as in Fig. 4.4), the following abnormal conditions will result:
• Theresistancesoftheconnectingcableswillnotbebalanced.
• Theindividualbatterieswillseedifferentseriesresistances.
• Alltheindividualbatterieswillbechargedatdifferentchargingcurrentandthus,
will reach fully charged state at different times.
• Thebatterywithlowerseriesresistancewilltakeshortertimetochargeas
compared to the battery which sees higher series resistance and hence, will
experienceovercharginganditslifewillbereduced.
Sizing Inverter Battery Bank
The following basic rules are used to determine the size of the battery bank:
• ActivePowerinWatts(W)=
VoltageinVolts(V)xCurrentinAmperes(A)xPowerFactor ...................... Formula 1
• Foraninverterrunningfroma12Vbatterysystem,
the DC current required from the 12V batteries is the
AC power delivered by the inverter to the load in Watts (W)
divided by 10 ..................................................................................................... Formula 2
• Energyrequiredfromthebattery=
DCcurrenttobedelivered(A)xtimeinHours(H) ........................................ Formula 3
• AsaRuleofThumb,Ahcapacityofthebatteriesrequired=
2xEnergyrequiredfromthebattery ............................................................. Formula 4
SECTION 4 | Installation