6
although it’s a bit less convenient since you have to find that window then press the minus key. Not so good if you
need to shut off the engine quickly for some reason.
Optional Backup Battery mounting kit, and wiring connections
Mount the backup battery cnc holder to the airframe. The battery kit pictured
here, there are 4 countersunk mounting holes in the bottom of the battery
bracket using #10 flathead screws. Do not mount the battery close to a hot
surface where there would be exhaust heat on the other side of the
aluminum. AGM batteries can be mounted in any orientation since they do
not leak. There is no need to switch the battery power to the CPi2. When the
CPi2 is powered off the current drain on the battery is only 0.0000016A, on a
Single board and .0000032A on a Dual board CPi2. Route the wire harness
from the battery to where the ecu is located and plug it into the left side of the
ecu as shown in the ecu photo below.
Using your own backup battery
If you are connecting to your own
already installed backup battery then you will need to mount one or two ATC
fuse holder(s) close to your backup battery. One fuse holder for single board,
two for dual board ecu’s. Battery wiring harness-red to fuse, then fuse to
battery plus, black to battery minus. For the dual board CPi2 the same
applies for the 2
nd
battery harness. 15 amp ATC fuses should be used for the
backup battery.
Battery grounding, important.
If your backup battery is powering devices other than the CPi2, then you
should connect the battery minus to your grounding bus or chassis ground. If the battery is only being used for the
CPi2, there is no need to chassis ground the battery, as it will ground via the CPi2 ecu and harnesses.
Green Tachometer signal output wire
This wire outputs a 12 to16 volt square wave signal to drive instrument panel tachometers. Be sure your instrument
can accept a 12 to 16 volt signal before you connect this wire, most should, but consult your manual.
Use the green wire from the primary main harness.
For Garmin G3X, connect to pin 8 J243, no pullup resistor is required, since there is a pullup resistor in the CPi2.
For Advanced Flight Systems 5000, Connect to pin33 electronic ignition input.
For Dynon skyview, connect to pin32 Standard RPM input wire. For Dynon, if you have removed a magneto, there
could be a 30K or similar resistor installed in the wiring which they require, but for the CPi-2 you must remove this
resistor since the CPi-2 tach output peak voltage is equal to your main bus voltage (less than 15). If the CPi-2
switches to backup power then peak tach signal voltage will equal the backup power source voltage.
On dual board CPi-2’s the backup harness green tach wire could be used for a secondary tach or instrument panel
or be unconnected. Connect to Dynon pin 33 or G3X pin 6 on J243
Programmer DB9 cable
Connects the ecu to the programmer. This is just a generic cable straight through type cable. The Dual Cpi2 unit
has only one programmer cable, which is all that is needed. A switching board spans the two main boards inside the
dual ecu allow the programmer to access each board separately by pressing the PROG key.
