Print this page

Powering the Base Unit

For most SiteMonitor systems, all power for the Base and Expansion modules is obtained from the base unit. As a result, the power requirements for the Base unit will vary widely.

The SiteMonitor System is designed to operate on voltages typically found in a 12, 24 or 48V battery system. The unit will actually operate on voltages up to 60V, so typical charging voltages found in a 48V battery system are acceptable. Just be sure to not exceed 60V under normal operation, and never exceed 62V under any conditions.

Note that the original base unit had a lower maximum voltage rating, up to an absolute maximum under any conditions of 30V. In addition, expansion modules with a Revision prior to revision H have the same limits. If you have either an original base unit, or you have earlier expansion modules (serial numbers prior to 32767), you must limit the power supply voltage to under 30V in all cases.

The amount of current needed for the SiteMonitor System will vary depending on the voltage provided to the unit. Higher supply voltages will generally result in lower current draw - but will also generally result in higher power consumption since some SiteMonitor components use the same current regardless of voltage.

Almost all smaller sitemonitor systems (up to a few expansion modules) will operate off of a 12V power supply at 1A, or a 24V or 48V power supply at 0.5A. When powering from a source capable of providing more than 2 Amps at whatever voltage it supplies, an external fuse is *REQUIRED*, prefererably in both the positive and negative power lines. The fuse should typically be 1A fast blow unless a lot of modules have been added to the system.

On the SiteMonitor base unit, there are two power inputs labeled as "Pwr1" and "Pwr2". Either or both of these inputs can be used to power the SiteMonitor unit. If both are connected, the SiteMonitor will draw power from the input with the highest voltage.

When operating at a site with both commercial and conditioned (UPS) power, we recommend connecting the SiteMonitor to two power sources - typically one which is derived directly from the commercial power, and one which is derived from the UPS power. This will permit two things - the first is the monitoring of commercial power availability separately from the UPS power. The second is permitting remote control of the conditioned power source without affecting the SiteMonitor availabilty.

When operating at a site with a battery system, we realize that only one power source is often available. As a result, we expect that many solar sites will only use one of the two power inputs. There is minimal benefit to connecting both power connections to the same source. We do not recommend connecting one of the power inputs directly to solar cells or a similar "unregulated" source, as the open-circuit voltage across a typical solar array will exceed the 30V maximum rating. In addition, it is important to ensure that any source connected to the power inputs is capable of providing sufficient current to power the unit - that is, don't try to use the unused power input as a spare "voltmeter input".

When connecting the power, it is important to observe proper polarity. In addition, it is important to understand that the negative on both inputs is electrically connected internally. Or stated differently... there is a wire internal to the sitemonitor which connects the - pin of Pwr1 with the - pin of Pwr2. If power is connected incorrectly, you can damage the sitemonitor simply by causing a short through this internal connection. As a result, we recommend verifying proper connection and polarity with a voltmeter before plugging the removable terminal strip into the unit.

To connect power, simply attach the power to the appropriate screw terminals, and attach to the unit (if the screw terminal block was removed to simply connections).

The use of the remaining terminals on the base unit is documented in the "Module Specifics" section of this document.