Samlexpower PST-15S-12E Owner's manual - Section 7 |
26 | SAMLEX AMERICA INC.
SAMLEX AMERICA INC. | 27
seCtIOn 7 |
General Information on lead Acid
Batteries
!
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), attention
should be paid to the manner in which the charger / inverter is connected
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 output 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.
7.16 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. Active Power in Watts (W) = Voltage in Volts (V) x Current in Amperes (A)
x Power factor.
2. for an inverter running from a 12V battery system, the approximate DC current re-
quired from the 12V batteries is the AC power delivered by the inverter to the load
in Watts (W) divided by 10 & for an inverter running from a 24V battery system, the
approximate DC current required from the 24V batteries is the AC power delivered
by the 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).
The first step is to estimate the total AC Watts (W) of load(s) and for how long the
load(s) will operate in hours (H). The AC Watts are normally indicated in the electrical
nameplate for each appliance or equipment. In case AC Watts (W) are not indicated,
formula 1 given above may be used to calculate the AC Watts. The next step is to
estimate the DC current in Amperes (A) from the AC Watts as per formula 2 above. An
example of this calculation for a 12V inverter is given below: