Remote Processing CX-10 - Manual (Page 31)

BATTERY CHARGER & POWER SECTION 8
Page 8-1
INTRODUCTION
BATTERY CHARGER & POWER SECTION 8
The CX-10 requires a minimum of 12 volts to operate.
Power may be from a line powered DC supply (1
ampere) or solar panel and lead acid battery.
The CX-10 incorporates a temperature compensated
battery charging circuit. The circuit is designed to
charge a lead acid type battery.
Battery voltage and switched battery voltage are
available at P2.
BATTERY CHARGER
Two charging rates are possible through register 4827. A
lower voltage float charge and a higher voltage charge.
The following table shows the theoretical charging
voltages at different temperatures.
Temperature
(

C)
Float
voltage
Charge
voltage
Ideal
charge
0 14.71 15.74 15.6
25 13.87 14.83 14.88
50 13.47 14.41 14.4
The temperature sensor is R24, located next to the “Batt
V adj.” pot. Under ideal conditions, this resistor would
be at the same temperature as the battery. When the CX-
10 is mounted in a box outside, it is probable that the
temperature in the box will differ from the battery. For
this reason, the battery, ideally, should be located near
R24.
Depending upon battery size and use, battery voltage
control may or may not be necessary. If relays will be on
when external power is missing (solar control), then
more active battery management is necessary. If the
battery is drained excessively, the hgher charge voltage
should be applied for an hour or two each day to prevent
sulfation. This can be done under modbus or Basic
program control.
Register 8 returns the supply voltage as a number
between 0 and 4095. Register 9 returns the battery
backup voltage as a number between 0 and 4095. To
convert this reading into volts, multiply by 0.007326.
In Basic, this is done as follows:
100 A = REGREAD(8) * 0.007326
Project 3 will also return supply (charging) or battery
voltage when registers 1-12 are returned.
POWER CONNECTIONS
DC power to the CX-10 is usually to P4 to the terminal
marked “Ext. Pwr”. Use this terminal for solar panel
power and AC line power DC supplies with voltages
above 12 volts. Maximum voltage at this terminal is 26
volts DC.
If you are not connecting a battery backup to the CX-10
(or you are taking power from another device that is
charging a battery), and your DC voltage in is under 15
volts, then apply power to the “Batt” terminal on P4.
Battery Backup
The CX-10 has a temperature compensated lead acid
battery charging circuit. It can, under program or
modbus control, change between float and charging
voltages.
Virtually any size battery may be connected. Maximum
charging current is limited, however. Charge current
depends upon temperature around the CX-10, charging
(solar panel) voltage, and current demanded by the CX-
10 at the time.
A combination of high charging voltage (solar noon),
high temperatures, and CX-10 current draw due to
energized relays, opto inputs, and RF modem
transmission could cause the CX-10 to draw power from
the battery.
As a general rule, relays will not be energized all the
time when used in remote applications. Battery sizes of
7-12 AH should be adequate in many instances.
However, if relays are frequently energized, especially at
night, then a larger battery may be necessary.
Other Power Connections
Continuous and switched +5V and battery power are
available at several connectors for different purposes.
Switched +5V is available at both RS-232 serial ports at
pin 8. Pin numbering from the top of the PCB is shown
below.