Campbell CH201, Product Manual

Page: 29 / 44

7. Operation
This section covers the following:
7.1 Charging algorithm 19
7.2 Maximum power point tracking 20
7.3 Communications 21
7.3.1 SDI-12 communications 23
7.3.2 RS-232 communications 25
7.4 LED indicators 29
7.1 Charging algorithm
The CH201 uses a two-step constant voltage charging algorithm, which is the preferred method
for rapidly charging VRLA batteries
1
from a solar panel. If the CH201 is powered solely from a
continuous power supply, bypass the two-step charging and use continuous, unaggressive
charging by using the battery capacity setting of zero (default value). When powered from a solar
panel, the battery charge deficit (Qloss) is compared to the specified battery capacity to
determine if aggressive cycle charging is necessary. Cycle charging is used if Qloss is determined
to be greater than 20% of the battery capacity. Upon detection that the battery is near full
charge, the constant voltage charging level is reduced from the aggressive cycle charging voltage
to the non-aggressive float-charge voltage to prevent overcharging and unwanted gassing of the
battery.
If the battery capacity is left at the default value of zero, Qloss always equals 0, which disables
cycle charging. Consequently, CH201 users must enter the battery capacity in the Device
Configuration Utility to enable the aggressive cycle charging capability of the two-step constant
voltage charging algorithm that is optimal for charging from solar panels.
Discharged VRLA batteries can initially accept large charging currents, often resulting in the
charger being unable to initially maintain a constant voltage because of current limiting by the
charge source or the charger itself. As a result, a typical two-step constant voltage charging cycle
usually consists of three distinct stages; a current limited charge stage, a constant cycle voltage
charge stage, and a constant float voltage charge stage (see
FIGURE 7-1 (p. 20)). The current
limited stage and/or the constant cycle charge voltage stage may not occur if the battery size is
CH201 12V Charging Regulator 19