Samlex America PST-200S-24E - Manual (Page 25)

24 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 25
seCtIOn 7 | General Information on Batteries for
Powering Inverters
teries to form a 12V, 400 Ah battery bank. Two 6V, 200 Ah batteries, Batteries 1 and 2
are connected 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.
!
cAUtion!
When 2 or more batteries / battery strings are connected in parallel and are
then connected to an inverter or charger (See figs 7.3 and 7.4 given above),
attention should be paid to the manner in which the charger / inverter is con-
nected to the battery bank. Please ensure that if the Positive output cable of
the battery charger / inverter (Cable “A”) is connected to the Positive battery
post of the first battery (Battery 1 in fig 7.3) or to the Positive battery post of
the first battery string (Battery 1 of String 1 in fig. 7.4), then the Negative out-
put cable of the battery charger / inverter (Cable “B”) should be connected to
the Negative battery post of the last battery (Battery 4 as in fig. 7.3) or to the
Negative Post of the last battery string (Battery 4 of Battery String 2 as in
fig. 7.4). This connection ensures the following:
- The resistances of the interconnecting cables will be balanced.
- All the individual batteries / battery strings will see the same series resistance.
- All the individual batteries will charge / discharge at the same charging
current and thus, will be charged to the same state at the same time.
- None of the batteries will see an overcharge condition.
Sizing the inverter Battery Bank
one of the most frequently asked questions is, "how long will the batteries last?" This
question cannot be answered without knowing the size of the battery system and the
load on the inverter. Usually this question is turned around to ask “How long do you
want your load to run?”, and then specific calculation can be done to determine the
proper battery bank size.
There are a few basic formulae and estimation rules that are used:
1. Power in Watts (W) = Voltage in Volts (V) x Current in Amperes (A).
2. for an inverter running from a 12V battery system, the DC current required from
the 12V batteries is the AC power delivered by the inverter to the load inWatts (W)
divided by 10 & for an inverter running from a 24V battery system, the DC current
required from the 24V batteries is the AC power delivered bythe inverter to the
load in Watts (W) divided by 20.
3. Energy required from the battery = DC current to be delivered
(A) x time in Hours (H).