User Guide
9
of the panels. To work out this figure the details of the exact site of
installation are required. This is because the amount of energy that can be
captured varies with latitude and local climate.
It is generally advisable to have at least one month’s capacity in the battery,
assuming that the panel provides no power. This allows for periods of bad
weather, which apart from causing less solar radiation might also result in
snow or ice build-up on the panel surface, thus reducing the panel output
further.
Technical Note 12, ‘Calculating Power Consumption and Solar Panel Size’ gives
much more information on this subject, and is available on request.
When estimating the battery capacity, remember to allow for any
reduction caused by low temperatures.
It is possible to deviate from these rules in many circumstances, e.g. a smaller
panel might be used if only operating in the summer months. In some
circumstances it is also more cost effective to opt for a much larger battery to
cover several months in the winter than to buy a much larger panel to give positive
charging at all times.
If a larger battery is to be used with an existing power supply system (e.g. a PS
power supply), either disconnect the existing supply altogether or connect the
external battery to the existing supply using a diode/resistor connection technique
(see Figure 6). This gives some protection against reverse polarity connection and
also guards against excessive current flowing when the external battery is first
connected to the internal battery.
Figure 6. Connecting to External Power Supply
If using this connection it is essential to connect the solar panel and shunt regulator
directly across the external battery. The battery voltage monitored by the logger
will be 0.7V lower than the voltage on the external battery.
When using external lead acid batteries it is good
practice (and sometimes a legal requirement) to fit a fuse
in the leads coming from the battery so the accidental
shorting of the leads does not lead to overheating of the
cables or a fire.
NOTE
WARNING
IN4001 3 ohm 5 watt
