Mastervolt SCM20 PWM, Installation Manual, Page: 10 / 16

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EN / SCM20 & SCM40 PWM User’s Manual
3.4 SPECIFICATIONS OF THE PV ARRAY
WARNING
When the PV array is exposed to light, it
supplies a DC voltage to the Solar
Chargemaster which can be dangerous to touch.
For this reason, use of an external DC-switch is
strongly recommended. Alternatively, before
attempting any maintenance or cleaning the PV-
array should be protected from light exposure,
e.g. by covering the PV modules.
CAUTION!
Do not connect Solar Chargemasters in parallel
on the side of the PV array.
The Solar ChargeMaster is appropriate for nominal 12V
and 24V solar systems. The table shows the number of
cells required for the nominal voltages.
Battery voltage U
NOM
= 12V
Model Panel type
Max input
voltage Max input
current
SCM20 PWM 36 cells 28V 20A
SCM40 PWM 36 cells 28V 40A
Battery voltage U
NOM
= 24V
Model Panel type
Max input
voltage Max input
current
SCM20 PWM 72 cells 55V 20A
SCM40 PWM 72 cells 55V 40A
CAUTION!
Never connect voltages higher than specified to
the PV-input, as this will cause permanent
damage to the Solar Chargemaster.
Configuration examples for PV-arrays consisting of
monocrystalline or polycrystalline PV-modules:
3.5 CONNECTION OF LOADS
Depending on the energy system in which the Solar
Chargemaster is used, there are two options to connect the
electrical load to the Solar Chargemaster:

To the Load output on the Solar Chargemaster, or

Directly to the battery.
3.5.1 Load connected to the Load output
See Figure 5 for a typical installation diagram. The Load
output is provided with a protection circuit that switches off
the connected load automatically in case of overload or if
the battery voltage is too low. This kind of installation is
typically used when the PV-modules are the only source of
electrical power to charge the battery.
3.5.2 Load connected to the battery
If the maximum load will exceed 20 Amps (SCM20 PWM),
40 Amps (SCM40 PWM) or if the battery will also be
charged by other energy sources, such as a battery
charger or an alternator, the electrical load shall be
connected to the battery directly. See Figure 6 for a typical
installation diagram. In this situation the battery is no longer
protected against too low battery voltages. Installation of
additional undervoltage protection circuits may be
necessary. See section 5.3 for ordering information
3.6 THINGS YOU NEED
Make sure you have all the parts you need to install the
Solar Chargemaster:

Solar Chargemaster (included);

Battery temperature sensor with cable and plug
(optional, not included; see section 5.3 for ordering
information);

DC cables to connect the Solar Chargemaster; see
section 3.3 for specifications;

DC-fuse holder with a DC-fuse, to be integrated in the
positive DC-cable to the battery; see section 3.3;

Screws / bolts (Ø 4mm max.) (with plugs) to mount the
Solar Chargemaster to a surface;

Batteries;

Appropriate and reliable cable terminals, strain reliefs,
battery terminals and boot lace ferrules.
We recommend as a minimum tool kit:

Phillips screw driver nr.2 or flat blade screw driver 5
mm to fix the DC-cables;

Tools to fix the screws / bolts with plugs to mount the
Solar Chargemaster to a surface;